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DANIAL ASYRAF BIN DAHARI MOHD 2021601352

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DANIAL ASYRAF BIN DAHARI MOHD 2021601352

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MUHAMMAD FARIS HUSAINI BIN ROHISHAM 2021615452

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MUHAMMAD FARIS HUSAINI BIN ROHISHAM 2021615452

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For a simple and scientific explanation of floods and different types of floods, visit this link. The language is simple and the concepts are clearly explained in this site. See the diagrams to understand how the landscape changes when floods occur.

Causes of floods
To understand how floods are caused, the extent to which they can be considered as "acts of God" and how the activities of man can make floods more or less severe, read this comprehensive guide here.

It is written mainly for insurance companies, builders and other professionals and talks mostly of flooding in UK. But it is very informative as the basic facts remain the same- the change in landscape, land use, how the size of the river basin and the flood plain affects the severity of floods, and how we can prepare for floods in a flood prone area.

1998: A year of floods
One of the nature's most turbulent years was 1998. Floods wreaked havoc in North America, South America, Asia and Europe. Though the El Nino and La Nina were thought to be responsible for these floods, scientists have now found out that these factors combined with global warming caused by pollution and made the disasters more severe.

Deforestation and global warming are cited as two of the main man-made causes that led to such a disastrous year with loss of lives and huge damage. Read these reports from BBC network on some of the worst floods and the devastating effect of Hurricane Mitch - all testimonies to the result of human activity interacting with natural phenomena.

Are man-made floods possible?
A debate around the world is that nature is to blame for natural hazards while one section says that man causes or triggers these hazards by deforestation and pollution. In China, a flood affected the lives of 250 million people and caused large scale devastation and the El Nino was cited as the main cause.

But after some analysis, it has been found that it was caused by large scale deforestation leading to loose soil and therefore huge floods. Read this article to know more about this debate.

How are floods caused by man? How do man-made changes in a river basin affect floods? In Washington, floods are caused by man-made actions. The rapid urbanization of Washington has led to more concrete surfaces that seal the surface and do not allow water to seep in.

Dikes can help contain the water but they also cut off the river from the floodplain. The floodplain helps to retain some of the floodwater but cutting the river off from it means that this natural storage is gone. The consequent pressure on the environment leads to such disasters. Download this report to find out more.

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For a simple and scientific explanation of floods and different types of floods, visit this link. The language is simple and the concepts are clearly explained in this site. See the diagrams to understand how the landscape changes when floods occur.

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Floods are the most frequent type of natural disaster and occur when an overflow of water submerges land that is usually dry. Floods are often caused by heavy rainfall, rapid snowmelt or a storm surge from a tropical cyclone or tsunami in coastal areas.

Floods can cause widespread devastation, resulting in loss of life and damages to personal property and critical public health infrastructure. Between 1998-2017, floods affected more than 2 billion people worldwide. People who live in floodplains or non-resistant buildings, or lack warning systems and awareness of flooding hazard, are most vulnerable to floods.

There are 3 common types of floods:

Flash floods are caused by rapid and excessive rainfall that raises water heights quickly, and rivers, streams, channels or roads may be overtaken.

River floods are caused when consistent rain or snow melt forces a river to exceed capacity.

Coastal floods are caused by storm surges associated with tropical cyclones and tsunami.

Between 80-90% of all documented disasters from natural hazards during the past 10 years have resulted from floods, droughts, tropical cyclones, heat waves and severe storms. Floods are also increasing in frequency and intensity, and the frequency and intensity of extreme precipitation is expected to continue to increase due to climate change.

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Many people in the United States live in coastal areas or regions with high precipitation that experience natural flooding often. Residents of these flood prone areas generally know when to expect flooding and what to do to protect their homes from its effects. People that do not live in flood prone areas must understand that natural flooding can happen literally anywhere in the United States. While the risk of flooding is much lower in certain areas, the right combination of causes and conditions can still lead to serious flooding that can result in property damage. It is important to know how natural floods occur as well as the most common causes of flooding so you can protect yourself and your property.

How Floods Form

Most natural floods form when the ground becomes too saturated to absorb excess water quickly enough. Once the soil has absorbed as much of the flood water as it can, the water starts to accumulate on the surface and spread out into new areas. This may also occur if the soil is too dry and hardened to absorb water. The flood water becomes much more dangerous as it begins to pick up power and speed. Moving flood water has the power to pick up debris and seriously damage anything in its path. It only takes 6 inches of flood water to take down a person and your car can get taken away in just one foot of water. As the flooding gets worse, it can potentially take down power lines, damage homes and buildings, and even result in death.

The condition of the soil is a good indicator of your risk of flooding. If the ground in your area is extremely wet or dry and you expect a storm or heavy rain, you must prepare for the possibility of a flood.

Common Causes of Flooding

There are several potential weather-related and man-made causes of significant flooding. The most common causes include the following:

Broken Levees and Dams: Dams and levees are built to protect the most flood prone areas of the U.S. When they become damaged or overloaded, disastrous flooding occurs because the water that was contained will rush into the surrounding areas at dangerous speeds. Levees and dams can become worn out or damaged over time which puts the area at a much higher risk of flooding. Broken levees caused much of the flooding in New Orleans from Hurricane Katrina.

New Construction and Land Development: New construction and land development on previously unused land affects the natural drainage of the area. With more land devoted to construction for new homes and buildings, there is less natural land to absorb excess water. This makes newly developed areas prone to flooding.

Hurricanes and Tropical Storms: Severe weather conditions and storms are common causes of flooding. Hurricanes bring an excessive amount of rain in a very short period of time and the powerful winds can cause huge waves to crash ashore. This amount of water is too much for drainage systems to handle which leads to very serious flooding.

Heavy Rain: It doesn't take a severe tropical storm to cause flooding, excessive rain is enough to cause floods in the right conditions. Enough rain can oversaturate the soil, cause rivers and creeks to rise, and cause storm drains to backup. Every area of the U.S. experiences heavy rain from time to time which means that there is potential for flooding anywhere.

Melting Snow: Any area that has experienced a significant amount of snow is at risk for flooding when the snow melts. Snow and ice melts quickly when the temperatures get warm enough and the ground may be too oversaturated or frozen to absorb it. The runoff can accumulate to cause flooding in residential areas and find its way into natural bodies of water like rivers and creeks.

By knowing and understanding the common causes and conditions that lead to flooding, you can assess your risk and react accordingly. If your home or building experiences indoor flooding or flood damage, contact a professional right away for water damage restoration. These professionals have state-of-the-art extraction equipment to remove flood water and they can also restore your home or building to its original condition.

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Many people in the United States live in coastal areas or regions with high precipitation that experience natural flooding often. Residents of these flood prone areas generally know when to expect flooding and what to do to protect their homes from its effects.

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Introduction

Most flooding occurs when the volume of water in a river or stream exceeds the capacity of the channel. Flooding also takes place along lake and coastal shorelines, when higher than normal water levels inundate low-lying areas.

Numerous factors affect streamflow, and therefore the potential for flooding. Most important are the amount and type of precipitation, the nature and condition of the drainage basin, and climate.

Precipitation

All rivers are subject to fluctuations in flow. During a rainstorm, the amount, intensity, duration, area of storm, and path of the storm all influence the runoff reaching the stream. The amount, intensity, and duration of storms affect the ability of the land to absorb the precipitation and therefore affect the rate of runoff. The area and path of the storm relate to the area of the basin receiving rainfall, which in turn, represents the area contributing runoff. The area and the runoff rate determine the volume of water that will pass a given point downstream.

Drainage basins

The shape, size, soil type, and topography of the drainage basin are other factors affecting the quantity of water reaching the stream. These factors are usually constant. However, the absorptive or shedding properties of the soil vary with vegetation cover, season, and previous rainfall.

In the case of reforestation and revegetation, the rate at which surface water flows to the main channel may be slowed, and hence the runoff is spread over a longer period. In addition, the passage of water tends to be retarded in basins with many natural storage areas, such as lakes and wetlands, and even those with artificially created storage. Consequently, smaller peak flows are produced than in basins without these modifying influences. The best North American example of a basin with large natural storage is that of the St. Lawrence River, which has the Great Lakes in its headwaters.

Climate

Climate has an important influence on the relationship between precipitation and runoff. Frost makes most soil impenetrable if the soil contains moisture. In northern latitudes, the winter season, during which a large part of the year's precipitation is stored in the form of snow, is often followed by sudden melting, with much of the runoff flowing quickly over frozen ground to reach streams. Also, the heavy ice formation on rivers influences flooding, particularly on the northward flowing rivers. Climate controls the strength of an ice cover in winter, and its manner of breakup, which governs the severity of ice jamming.

Snowmelt Runoff

During the Canadian winter, most of the precipitation is simply stored as snow or ice on the ground. During the springmelt, huge quantities of water are released, which explains our heavy spring runoff and flooding. This is called freshet.

Snowmelt runoff floods are the most common type of flooding in Canada. These floods generally occur in the spring but will also occur during sudden winter thaws. Heavy runoff results from the rapid melting of the snow under the combined effect of sunlight, winds, and warmer temperatures. When the ground is frozen, the water produced by the melting snow is unable to penetrate and runs off over the ground surface into streams and lakes. The amount of surface runoff is usually within the capacity of the channel to drain off without flooding. However, if there is an above-average snow depth, a sudden thaw, or both, then the potential for high volumes of runoff and subsequent flooding increases. The situation can become of even greater concern if the rising snowmelt runoff is compounded by runoff from heavy rainfall. The later the thaw, the more likely this situation will prevail. Since the climatic factors influencing the rate of snowmelt are often widespread, snowmelt runoff flooding conditions can exist over vast areas.

Rainfall

Flash floods can be extremely dangerous. Unanticipated, they usually happen on small watersheds as a result of a torrential downpour, often caused by heavy thunderstorm activity.

A flash flood is characterized by the occurrence of the peak of the flood within six hours of the onset of rainfall. The flood conditions develop rapidly because the rainfall is so heavy the ground is incapable of absorbing the water quickly enough, resulting in a very high runoff rate. The events are generally locally intense and damage is usually restricted to a limited area. Large rivers remain unaffected, while smaller streams can overtop their banks, even in a drought year.

Several notable flash flood events have occurred in Canada. During a storm at Harrow, Ontario, in July of 1989, over 400 millimetres of rain fell in 30 hours. In Quebec, a spectacular flash flood struck Montreal on July 14, 1987. The most intensive rainfall in Canadian history happened on May 30, 1961, at Buffalo Gap, Saskatchewan. More recently, severe prairie convective thunderstorms have produced some of the highest rainfall rates and largest local floods in Canada ( e.g., in Calgary, Edmonton and Lethbridge, Alberta).

Source: Adapted from Handbook on the Principle of Hydrology, D.M. Gray, ed.

Ice Jams

Ice jams are a major cause of flooding in Canada. In fact, for most Canadian rivers, the annual peak water levels are due to ice jams. These jams result from the accumulation of ice fragments that build up to restrict the flow of water and then act as a temporary obstruction. Jams form during both the freeze-up and breakup periods, but it is usually the breakup jams that have the greater flooding potential. While national figures are not available, on a provincial scale, data for the Saint John River basin in Atlantic Canada indicate that over two thirds of total provincial flood damage costs are due to ice-related events. The section on "Flood events in Canada" contains descriptions of ice jam flooding of the Saint John, St. Lawrence and Winisk rivers.

During the freeze-up period, ice forms on the river surface beginning at the banks. Ice crystals may also develop within the river as frazil ice, in open turbulent water under supercooled conditions, that is, the temperature of the water is slightly below 0 °C. It is very common in rapids. The ice crystals tend to coalesce and accumulate, and may become attached to the underside of the ice cover or to the river bed as anchor ice.

The coalescing frazil can also form flocs, which float to the surface when stream turbulence is reduced or when the buoyancy of a growing mass exceeds downward turbulence. The flocs continue to agglomerate and produce pans, which, in turn, may freeze together creating ice floes. Frazil pans and flocs are major components in the formation of a river's initial ice cover. In tranquil reaches, this cover is a mere surface layer of ice floes and pans, but elsewhere it can be several layers thick.

Ice jams during the freeze-up period usually form where floating ice slush or blocks encounter a stable ice cover. The beginning of the ice jam is referred to as the toe and the upstream end as the head. The stable ice is frozen to the banks or is restricted from moving by the channel configuration. Generally, incoming ice fragments either submerge and deposit under the stable ice cover or pile up behind it, or both. There are, however, certain features that, in conjunction with ice cover, or on infrequent occasions, alone, enhance the probability of ice jam formation: bridge piers, islands, bends, shallows, slope reductions, and constrictions.

During breakup in the spring, or during winter thaws, an ice jam results from the accumulation of ice from the breakup of the upstream ice cover. A rise in water levels may result from the spring snowmelt, or common to the southern and Atlantic parts of Canada, a sudden midwinter thaw. Midwinter thaws are often accompanied by substantial rainfall, resulting in a rapid increase in water levels and severe ice jams.

The ice cover may be broken in a major fashion due to uplift pressures exerted by rapidly rising water levels. This causes "hinge cracks," or longitudinal fracture lines parallel to the shores. The cover breaks down into smaller pieces after being set in motion by the flow and impacting with channel boundaries or other sections of ice cover.

Ice jams cause flooding because of two main features. First, ice jam thickness can be considerable, amounting to several metres. Secondly, the underside of the ice cover is usually very rough. Under open water conditions, the only frictional resistance retarding the flow of the water is the streambed. The rougher the streambed, the greater the depth required to pass a given discharge. With an ice jam in place, the additional ice and very rough lower surface retard flow. Therefore, the flow depth has to be much greater than for open water.

If the depth of water necessary to float the jam is added to the depth required to maintain the discharge, it can be seen that extremely high water levels can occur, even at relatively small discharges.

Another potentially damaging condition closely related to ice jam flooding is the surging flow produced by the sudden release of a major ice jam. Flow surges can move as fast as 10 metres per second, or 36 kilometres per hour, which implies that the water level could rise rapidly, allowing little time for emergency measures. Moreover, the velocity of water and floating ice can also be very high, more than 5 metres per second, or 18 kilometres per hour, with the potential for serious erosion or ice impact damages.

Anecdotes

Insight, Alberta Public Safety Services: Spring breakup in Fort McMurray, Alberta, draws crowds each year but the possibility of flooding caused by ice jams is an annual worry.

Betty Brown, Vars, Ontario: As a child growing up on a farm beside the Becaguimec River In New Brunswick, I remember my father in the spring getting the tractor and hauling the outhouse and pigpen away from the river. Over the years we lost a good many outhouses.

During the breakup, we would hear a rumbling noise that sounded like thunder. The ice practically grazed the side of our house, Some of the chunks were the size of our house. One year, my dog got stranded on the ice and my mother rescued him. Daily my brother and I would watch for "strange" stuff. We would see pots and pans, balls and bats, inner tubes, uprooted trees go by... Living in the country, spring breakup is a highlight of the year.

Catastrophic Outbursts

Outburst floods are common in western Canada. Lakes dammed by glaciers or moraines suddenly drain and tonnes of water, mud and debris are released.

Outbursts from glacier-dammed lakes are known as "jökulhlaups," an Icelandic term. An outburst flood typically occurs when the water level becomes high enough to actually float the ice or when a small channel forms under the ice and causes rapid melting, thus expanding the channel. Another common mechanism is overtopping of the ice dam and the rapid thermal and mechanical erosion of a channel, leading to catastrophic drainage. In all cases, the new channel increases rapidly in size and releases the lake water quickly. The release of water is often sudden and catastrophic. Many glacier-dammed lakes have been known to empty and refill a number of times. The typical discharge pattern of outburst floods is illustrated in this hydrograph.

Outbursts from moraine-dammed lakes are less common but can be just as destructive. In the case of these lakes, water overtops and cuts through the moraines. There is also the possibility, with recent lakes, of failure of the dam caused by seepage through the moraine once the internal ice core has melted away.

Floodwaters from glacier- and moraine-dammed lakes can pick up large quantities of sediments and transform into destructive debris flows. This water-saturated, bouldery debris rushes down valley, ripping sediments and trees from the valley floor.

Many jökulhlaups have occured in western Canada in recent years. A description of a jökulhlaup at Kicking Horse Pass, British Columbia is presented in the section on "Flood events in Canada". The locations of others, including those from Hazard Lake in the St. Elias Mountains and from Tulsequah, Flood, Summit and Ape lakes in the Coast Mountains, are represented on the following map.

Coastal Storms

Many Canadians living along the shores of major lakes, such as the Great Lakes, or along Canada's coasts have experienced flooding and property damage as a result of high wind and wave action, or the interaction between high estuarine flows and tides. Shoreline flooding may be caused by storm surge or seiches, often occurring simultaneously with high waves.

Any body of water has a set of natural periods of oscillation at which it is easy to set up motions, which are called seiches. The periods of these seiches, which are dependent on the water depth and the horizontal dimensions of the body of water, can range from several minutes to several hours. They occur commonly in enclosed or partially enclosed basins and are usually the result of a sudden change, or a series of intermittent-periodic changes, in atmospheric pressure or wind velocity. The period of oscillation of a seiche depends on the causative force which sets the water basin in motion and the natural or free oscillating period of the basin. For example, when the wind ceases, the effort of the water to return to equilibrium may create an oscillation at a period unique to the region of occurrence.

The appearance of these seiches can be simulated by tilting a basin partially filled with water and then setting it down on a level surface. The water will slosh back and forth at a period determined by the size and shape of the basin. The maximum amplitude of a seiche in a closed basin occurs at the ends; the point of no vertical change occurs at the middle.

Storm waves from Lake Erie wash over a beach and picnic area at Point Pelee National Park, Ontario (Public Works and Government Services Canada / Richard Vroom, 1976)

Surges are caused by sudden changes in atmospheric pressure and by the wind stress accompanying moving storm systems. Storm systems are significant because of their frequency and potential for causing abnormal water levels at coastlines. In many coastal regions, maximum storm surges are produced by severe tropical hurricanes. Determination of water elevations during storms is a complex problem involving interaction between wind and water, and differences in atmospheric pressure. Winds are responsible for the largest changes in water level due to surge. A wind blowing over a body of water exerts a horizontal force on the water surface and induces a surface current in the general direction of the wind. These currents are impeded in shallow water areas, causing the water level to rise downwind while at the windward side of the basin the water level falls. The term "storm surge" is used to indicate departure from normal water level due to the action of storms. The term "wind setup" is often used to indicate rises in lakes, reservoirs, and smaller bodies of water. A fall of water below the normal level at the upwind side of a basin is called setdown.

Along the coasts of Canada, severe storms can produce surges of up to 2 metres, but in some areas of the world, notably Bangladesh, severe storms can produce surges in excess of 8 metres. Generally, setups in lakes and reservoirs are less. Among the most extreme lake set-ups observed in the world are those on Lake Erie, amounting to 2.5 metres at the eastern end of the lake. These rises in water levels can also provide a base on which high waves can attack the upper part of a beach and penetrate farther inland. Wind-induced surge, accompanied by wave action, accounts for most of the damage to coastal structures and beach areas. Specific types of coastal flooding events include tsunamis and, cyclones and hurricanes.

The section on "Flooding events in Canada" contains additional information on both Great Lakes and Tuktoyaktuk flood events.

Tsunami

The most spectacular coastal flooding event is the tsunami, also known as a tidal wave. The term "tidal wave" is actually incorrect, as tidal activity is not a component of the event.

The Japanese word tsunami means " harbour wave".

A tsunami is a wave set in motion by an undersea movement such as an earthquake or a landslide where the disturbance gives a vertical motion to the water column. An earthquake of 7.0 on the Richter scale is sufficient to generate a series of waves. The resulting set of waves have been known, in the Pacific Basin, to travel at up to 960 kilometres per hour over long distances with little loss of energy. Crests can be several hundred kilometres apart and hardly noticeable on the open sea. As a wave approaches the coast it grows as it slows down and builds up on top of itself in the shallower water. The mass of water that hits the shore still has tremendous velocity as well as force behind it.

The wave that hits the coast is rarely the breaking wave that is commonly perceived, but appears as a rapid rise in the water level. The first wave is often preceded by a lowering of the water level and the draining of harbours, bays, inlets, etc.

Tsunamis are unique with respect to location, amplitude of waves, and time between troughs. They behave like shallow water waves, as their direction is affected by the bottom topography. Topographic information is one of the parameters used in modelling scenarios, but the modelling is crude because the source of the wave is unknown.

For more information on tsunami, see Tsunami strikes the East Coast and Tsunami strikes the West Coast in the section on "Flooding events in Canada".

Cyclones and hurricanes

The dominant type of storm in Canada is the mid-latitude or extratropical cyclone. These are low pressure systems that move from west to east across the country and are typified by the counterclockwise rotation of the associated warm and cold fronts.

Most large-scale flooding associated with extratropical cyclones is the result of precipitation adding to the spring snowmelt runoff or acting in combination with some other factor. Extratropical storms often travel in series and may result in considerable accumulation of precipitation over a long period, resulting in saturated soils becoming a contributing factor to flood conditions.

Tropical cyclones develop over warm tropical or subtropical water and are infrequent compared with extra-tropical storms. The tropical cyclone differs from the extratropical cyclone because it focuses energy in a small area. Only a few hundred kilometres away the weather can be calm. With the approach of a tropical cyclone the weather suddenly deteriorates into a violent maelstrom. The fury of such a cyclone is never forgotten by those who have experienced it. One such storm is Hurricane Hazel, which struck Toronto in 1954.

A tropical cyclone with winds of 64 knots or greater is called a hurricane. A mature hurricane ranges from several hundred to a thousand kilometres across.

Tropical cyclones affecting eastern Canada develop over the tropical or subtropical North Atlantic Ocean, Caribbean Sea or Gulf of Mexico. As the storm moves north over land or cooler water it begins to dissipate.

Tropical cyclones tend to follow seasonal tracks. The early season storms of June and July originate in the Gulf of Mexico and the western Caribbean Sea. These storms rarely affect eastern Canada. Those most likely to affect the Atlantic provinces originate in a broad band from Florida southeast to the Cape Verde Islands during August, September and October.

Source: Adapted from Bowditch, N American Practical Navigator. An Epitome of Navigation.

On average, three tropical cyclones per year affect or threaten to affect Atlantic Canada. However, this number can be considerably higher. In 1969, eight tropical cyclones affected the Atlantic provinces. Tropical cyclones can retain their force as far inland as Ontario. In a Transport Canada study of tropical storms that affected Ontario over the period 1900 to 1949, it was found that 25 tropical hurricanes had passed over or close to Ontario. Eight of these had produced weather characterized by extremely high winds and excessive precipitation.

When hurricanes travel inland

Hurricanes moving inland into a region of uniform temperature, i.e., into a homogeneous tropical air mass, do not reach far inland.

Hurricanes moving inland into a region with a substantial temperature gradient retain enough energy to move inland for a considerable distance.

Most dangerous to inland areas is the hurricane which arrives at the coast following a path almost parallel to a strong cold front which arrives simultaneously. In 1954 Hurricane Hazel met this condition.

A hurricane reaching the coast following a path which is nearly perpendicular to a front usually forms a frontal low which occludes rapidly. Heavy rainfall is not likely to spread far inland.

Source: List adapted from The October 15-16, 1954. Storm "Hurricane Hazel" in Ontario; Mason, Thomas and Boyd

Urban Stormwater Runoff

Urban stormwater runoff can cause the flooding of local rivers as well as of the urban area itself. Urbanization drastically alters the drainage characteristics of natural catchments, or drainage areas, by increasing the volume and rate of surface runoff. While the impact on major river systems may be minimal, the carrying capacity of small streams may be quickly exceeded, causing flooding and erosion problems. Often, the runoff from intense rainfall exceeds the carrying capacity of the sewer system, creating a backup in the system and hence the flooding of basements and of roads.

Dam Failure

Flooding can also result from the failure of dams or other hydraulic structures, when a veritable wall of water can go hurtling down the river channel. As might be expected, the suddenness and magnitude of such an event, which is almost always the result of human failure in design, construction or operation, has disastrous results.

Additional information is contained in the description of the Saguenay flood presented in the section on "Flooding events in Canada".

Return to Floods menu

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Most flooding occurs when the volume of water in a river or stream exceeds the capacity of the channel. Flooding also takes place along lake and coastal shorelines, when higher than normal water levels inundate low-lying areas. Numerous factors affect streamflow, and therefore the potential for flooding.

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Public mind map by Ahmad Fikri Mohd. Create your own collaborative mind maps for free at www.mindmeister.com

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A NASA analysis of a 2015 Texas flood is the first to document the full life cycle and impacts of a flood on both land and ocean.

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This page contains archived content and is no longer being updated. At the time of publication, it represented the best available science.

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Floods are primarily caused by naturally occurring changes in the height of rivers, lakes and oceans. According to Public Safety Canada, floods are the most com...

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The effects of a tsunami on a coastline can range from unnoticeable to devastating. The effects of a tsunami depend on the characteristics of the seismic event that generated the tsunami, the distance from its point of origin, its size ( magnitude) and, at last, the configuration of the bathymetry (that is the depth of water in oceans) along the coast that the tsunami is approaching.

Small tsunamis, non-destructive and undetectable without specialized equipment, happen almost every day as a result of minor earthquakes and other events. They are very often too far away from land or they are too small to have any effect when they hit the shore. When a small tsunami comes to the shoreline it is often seen as a strong and fast-moving tide.

Tsunamis have long periods and can overcome obstacles such as gulfs, bays and islands. These tsunamis make landfall usually in the form of suddenly decreasing and then rapidly increasing water levels (not unlike a tidal bore) a combination of several large waves or bore-type waves. Generally tsunamis arrive, not as giant breaking waves, but as a forceful rapid increase in water levels that results in violent flooding.

However, when tsunami waves become extremely large in height, they savagely attack coastlines, causing devastating property damage and loss of life. A small wave only 30 centimetres high in the deep ocean may grow into a monster wave 30m high as it sweeps over the shore. The effects can be further amplified where a bay, harbour, or lagoon funnels the waves as they move inland. Large tsunamis have been known to rise to over 100 feet!

The amount of energy and water contained in a huge tsunami can cause extreme destruction when it strikes land.

The initial wave of a huge tsunami is extremely tall; however, most damage is not sustained by this wave. Most of the damage is caused by the huge mass of water behind the initial wave front, as the height of the sea keeps rising fast and floods powerfully into the coastal area. It is the power behind the waves, the endless rushing water that causes devastation and loss of life. When the giant breaking waves of a tsunami batter the shoreline, they can destroy everything in their path.

Destruction is caused by two mechanisms: the smashing force of a wall of water traveling at high speed, and the destructive power of a large volume of water draining off the land and carrying all with it, even if the wave did not look large.

Objects and buildings are destroyed by the sheer weight of the water, often reduced to skeletal foundations and exposed bedrock. Large objects such as ships and boulders can be carried several miles inland before the tsunami subsides.

Tsunami waves destroy boats, buildings, bridges, cars, trees, telephone lines, power lines - and just about anything else in their way. Once the tsunami waves have knocked down infrastructure on the shore they may continue to travel for several miles inland, sweeping away more trees, buildings, cars and other man made equipment. Small islands hit by a tsunami are left unrecognizable.

Especially along a high seismic area, known as the Ring of Fire, tsunamis may have dramatic consequences as they hit less developed countries.

The buildings infrastructure in these poorer nations are not well built and cannot withstand the impact of the tsunami. Whole areas and towns are a picture of destruction as the tsunami leaves at trail devastation and misery behind it.

One of the biggest and worst effects of a tsunami is the cost to human life because unfortunately escaping a tsunami is nearly impossible. Hundreds and thousands of people are killed by tsunamis. Since 1850 alone, tsunamis have been responsible for the loss of more than 430,000 lives. There is very little warning before a tsunamis hits land. As the water rushes toward land, it leaves very little time to map an escape plan.

People living in coastal regions, towns and villages have no time to escape. The violent force of the tsunami results in instant death, most commonly by drowning. Buildings collapsing, electrocution, and explosions from gas, damaged tanks and floating debris are another cause of death. The tsunami of December 2004 that struck South East Asia and East Africa killed over 31,000 people in Sri Lanka only, leaving 23,000 injured.

Tsunami waves and the receding water are very destructive to structures in the run-up zone. The areas close to the coast are flooded with sea water, damaging the infrastructure such as sewage and fresh water supplies for drinking.

Flooding and contamination of drinking water can cause disease to spread in the tsunami hit areas. Illnesses such as malaria arise when water is stagnant and contaminated. Under these conditions it is difficult for people to stay healthy and for diseases to be treated, so infections and illnesses can spread very quickly, causing more death.

Tsunamis not only destroy human life, but have a devastating effect on insects, animals, plants, and natural resources. A tsunami changes the landscape. It uproots trees and plants and destroys animal habitats such as nesting sites for birds. Land animals are killed by drowning and sea animals are killed by pollution if dangerous chemicals are washed away into the sea, thus poisoning the marine life.

The impact of a tsunami on the environment relates not only to the landscape and animal life, but also to the man-made aspects of the environment. Solid waste and disaster debris are the most critical environmental problem faced by a tsunami-hit country.

Recycling and disposal of this waste in an environmentally sensitive manner where possible (crushing concrete, bricks, etc. to produce aggregate for rebuilding and road reconstruction) are critical.

Combined with the issue of waste is that of hazardous materials and toxic substances that can be inadvertently mixed up with ordinary debris. These include asbestos, oil fuel, and other industrial raw materials and chemicals. Rapid clean-up of affected areas can result in inappropriate disposal methods, including air burning and open dumping, leading to secondary impacts on the environment.

Contamination of soil and water is the second key environmental impact of a tsunami. Salination of water bodies such as rivers, wells, inland lakes, and groundwater aquifers can occur in most cases. This also affects the soil fertility of agricultural lands, due to salination and debris contamination, which will affect yields in the medium and long term. Sewage, septic tanks and toilets are damaged contaminating the water supply.

Last but not least, there may be radiation resulting from damage to nuclear plants, as it happened in Japan in March 2011. Since radiation exists for a long time, it has the capacity to inflict damage upon anything exposed to it. Radiation is most dangerous to animals and humans causing destruction as molecules loose their electrons. The damage caused by radiation to the DNA structure determines birth defects, cancers even death.

Massive costs hit communities and nations when a tsunami happens. Victims and survivors of the tsunami need immediate help from rescue teams.

Governments around the world may help with the cost of bringing aid to devastated areas. National institutions, the United Nations, other international organizations, community groups and NGOs , and a variety of other entities come together to provide different kinds of aid and services. There might also be appeals and donations from people who have seen pictures of the area in the media.

Reconstruction and clean up after a tsunami is a huge cost problem. Infrastructure must be replaced, unsafe buildings demolished and rubbish cleared. Loss of income in the local economy and future losses from the destruction of infrastructure will be a problem for some time to come.

The total financial cost of the tsunami could be millions or even billions of dollars of damage to coastal structures and habitats. It is difficult to put an exact figure on the monetary cost but the cost may represent an important share of a nation's GDP.

Victims of tsunami events often suffer psychological problems which can last for days, years or an entire lifetime. Survivors of the Sri Lankan tsunami of December 2004 were found to have PTSD (post traumatic stress disorder) when examined by the World Health Organization (WHO): 14% to 39% of these were children, 40% of adolescents and 20% of mothers of these adolescents were found to have PTSD 4 months after the tsunami.

These people were suffering from grief and depression as their homes, businesses and loved ones were taken from them. Many still had PTSD. Periliya Village counts 2,000 dead and 400 families became homeless. These people were found to still have psychological problems 2 years after the tsunami.

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tsunamis effects destruction death environmental impacts

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video earthquake tsunamis 2011 japan destruction

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Tsunami | Effects, large destruction of property and loss of life

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The effects of a tsunami on a coastline can range from unnoticeable to devastating. The effects of a tsunami depend on the characteristics of the seismic event that generated the tsunami, the distance from its point of origin, its size ( magnitude) and, at last, the configuration of the bathymetry (that is the depth of water in oceans) along the coast that the tsunami is approaching.

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What are tsunamis?

The word "tsunami" comprises the Japanese words"tsu" (meaning harbour) and "nami" (meaning wave). A tsunami is a series of enormous waves created by an underwater disturbance usually associated with earthquakes occurring below or near the ocean.

Volcanic eruptions, submarine landslides, and coastal rock falls can also generate a tsunami, as can a large asteroid impacting the ocean. They originate from a vertical movement of the sea floor with the consequent displacement of water mass.

Tsunami waves often look like walls of water and can attack the shoreline and be dangerous for hours, with waves coming every 5 to 60 minutes.

The first wave may not be the largest, and often it is the 2nd, 3rd, 4th or even later waves that are the biggest. After one wave inundates, or floods inland, it recedes seaward often as far as a person can see so the seafloor is exposed. The next wave then rushes ashore within minutes and carries with it many floating debris that were destroyed by previous waves. When waves enter harbors, very strong and dangerous water currents are generated that can easily break ship moorings, and bores that travel far inland can be formed when tsunamis entire rivers or other waterway channels.

What are the causes of tsunamis?

1. Earthquakes

It can be generated by movements along fault zones associated with plate boundaries. The region where two plates come in contact is a plate boundary, and the way in which one plate moves relative to another determines the type of boundary:

spreading, where two plates move away from each other;

subduction, where two plates move towards each other and one slides beneath the other;

transform where two plates slide horizontally past each other.

Most strong earthquakes occur in subduction zones where an ocean plate slides under a continental plate or another younger ocean plate.

All earthquakes do not cause tsunamis. There are four conditions necessary for an earthquake to cause a tsunami:

1. The earthquake must occur beneath the ocean or cause the material to slide into the ocean.

2. The earthquake must be strong, at least magnitude6.5 on the Richter Scale

3. The earthquake must rupture the Earth's surface and it must occur at shallow depth - less than 70km below the surface of the Earth.

4. The earthquake must cause vertical movement of the seafloor (up to several meters).

(source: http://weready.org/tsunami/index.php?option=com_content&view=article&id=8&Itemid=2 from - CDEMA[Carribean Disaster Emergency Management Agency])

2. Landslides

A landslide that occurs along the coast can force large amounts of water into the sea, disturbing the water and generate a tsunami. Underwater landslides can also result in tsunamis when the material loosened by the landslide moves violently, pushing the water in front of it.

(source: http://weready.org/tsunami/index.php?option=com_content&view=article&id=8&Itemid=2 from - CDEMA[Carribean Disaster Emergency Management Agency])

3. Volcanic Eruption

Although relatively infrequent, violent volcanic eruptions represent also impulsive disturbances, which can displace a great volume of water and generate extremely destructive tsunami waves in the immediate source area. According to this mechanism, waves may be generated by the sudden displacement of water caused by a volcanic explosion, by a volcanos slope failure, or more likely by a phreatomagmatic explosion and collapse/engulfment of the volcanic magmatic chambers.

One of the largest and most destructive tsunamis ever recorded was generated in August 26, 1883 after the explosion and collapse of the volcano of Krakatoa (Krakatau), in Indonesia. This explosion generated waves that reached 135 feet, destroyed coastal towns and villages along the Sunda Strait in both the islands of Java and Sumatra, killing 36, 417 people.
DIAGRAM SOURCE: GEOSCIENCE AUSTRALIA
4. Extraterrestrial Collision

Tsunamis caused by extraterrestrial collision (i.e. asteroids, meteors) are an extremely rare occurrence. Although no meteor/asteroid induced tsunami has been recorded in recent history, scientists realize that if these celestial bodies should strike the ocean, a large volume of water would undoubtedly be displaced to cause a tsunami. Scientists have calculated that if a moderately large asteroid, 5-6 km in diameter, should strike the middle of the large ocean basin such as the Atlantic Ocean, it would produce a tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States.

On both sides of the Atlantic, coastal cities would be washed out by such a tsunami. An asteroid 5-6 kilometers in diameter impacting between the Hawaiian Islands and the West Coast of North America, would produce a tsunami that would wash out the coastal cities on the West coasts of Canada, the U.S., and Mexico and would cover most of the inhabited coastal areas of the Hawaiian islands.

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The word "tsunami" comprises the Japanese words"tsu" (meaning harbour) and "nami" (meaning wave). A tsunami is a series of enormous waves created by an

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SHAH ALAM: Flash floods have hit Taman Sri Muda again after steady rainfall that began at 3pm Monday (Jan 24), raising concerns among residents.

Taman Sri Muda resident Balram Tikaram Kami, who was in his 30s, said many residents had panicked and driven their cars out of the area.

"A family member called me saying it was raining heavily.

"I passed by the Klang River in Taman Sri Muda when driving home but saw that the water levels were normal," Balram said.

He said most parts of Taman Sri Muda, which was flood prone, were not affected by the flash flood caused by Monday's rainfall.

Resident Subashini Karunakaran, 28, said the flooding was limited to the usual places where water rose whenever there was heavy rainfall.

"These locations are flood prone due to the problematic drainage system," the financial services executive said.

However, the authorities said the situation was under control and they were monitoring it.

Taman Sri Muda was heavily flooded during a heavy downpour on Dec 17 and there were even several deaths due to the tragedy.

Floodwaters had risen to almost the rooftop of single storey homes and with a lot of damage incurred to belongings and vehicles.

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Taman Sri Muda residents spooked by latest flood incident

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SHAH ALAM: Flash floods have hit Taman Sri Muda again after steady rainfall that began at 3pm Monday (Jan 24), raising concerns among residents. Taman Sri Muda resident Balram Tikaram Kami, who was in his 30s, said many residents had panicked and driven their cars out of the area.

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Snowmelt Runoff and the Water Cycle | U.S. Geological Survey

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Perhaps you've never seen snow. Or, perhaps you built a snowman this very afternoon and perhaps you saw your snowman begin to melt. Regardless of your experience with snow and associated snowmelt, runoff from snowmelt is a major component of the global movement of water, possibly even if you live where it never snows.

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Burning fossil fuels, cutting down forests and farming livestock are increasingly influencing the climate and the earth's temperature.

This adds enormous amounts of greenhouse gases to those naturally occurring in the atmosphere, increasing the greenhouse effect and global warming.

Global warming

2011-2020 was the warmest decade recorded, with global average temperature reaching 1.1°C above pre-industrial levels in 2019. Human-induced global warming is presently increasing at a rate of 0.2°C per decade.

An increase of 2°C compared to the temperature in pre-industrial times is associated with serious negative impacts on to the natural environment and human health and wellbeing, including a much higher risk that dangerous and possibly catastrophic changes in the global environment will occur.

For this reason, the international community has recognised the need to keep warming well below 2°C and pursue efforts to limit it to 1.5°C.

Greenhouse gases

The main driver of climate change is the greenhouse effect. Some gases in the Earth's atmosphere act a bit like the glass in a greenhouse, trapping the sun's heat and stopping it from leaking back into space and causing global warming.

Many of these greenhouse gases occur naturally, but human activities are increasing the concentrations of some of them in the atmosphere, in particular:

CO ₂ produced by human activities is the largest contributor to global warming. By 2020, its concentration in the atmosphere had risen to 48% above its pre-industrial level (before 1750).

Other greenhouse gases are emitted by human activities in smaller quantities. Methane is a more powerful greenhouse gas than CO ₂, but has a shorter atmospheric lifetime. Nitrous oxide, like CO ₂, is a long-lived greenhouse gas that accumulates in the atmosphere over decades to centuries. Non-greenhouse gas pollutants, including aerosols like soot, have different warming and cooling effects and are also associated with other issues such as poor air quality.

Natural causes, such as changes in solar radiation or volcanic activity are estimated to have contributed less than plus or minus 0.1°C to total warming between 1890 and 2010.

Causes for rising emissions

Burning coal, oil and gas produces carbon dioxide and nitrous oxide.

Cutting down forests (deforestation). Trees help to regulate the climate by absorbing CO₂ from the atmosphere. When they are cut down, that beneficial effect is lost and the carbon stored in the trees is released into the atmosphere, adding to the greenhouse effect.

Increasing livestock farming. Cows and sheep produce large amounts of methane when they digest their food.

Fertilisers containing nitrogen produce nitrous oxide emissions.

Fluorinated gases are emitted from equipment and products that use these gases. Such emissions have a very strong warming effect, up to 23 000 times greater than CO₂.

Countering climate change

As every tonne of CO ₂ emitted contributes to global warming, all emissions reductions contribute to slowing it down. In order to stop global warming completely, CO ₂ emissions have to reach net zero worldwide. In addition, reducing emissions of other greenhouse gases, such as methane, can also have a powerful effect on slowing global warming - especially in the short term.

The consequences of climate change are extremely serious, and affect many aspects of our lives. Both countering climate change and adapting to a warming world are top priorities for the EU.We need climate action now. Find out about what the EU is doing to fight the climate crisis.

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Burning fossil fuels, cutting down forests and farming livestock are increasingly influencing the climate and the earth's temperature.

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"If we don't have it, we don't need it," pronounces Daniel Fagre as we throw on our backpacks. We're armed with crampons, ice axes, rope, GPS receivers, and bear spray to ward off grizzlies, and we're trudging toward Sperry Glacier in Glacier National Park, Montana. I fall in step with Fagre and two other research scientists from the U.S. Geological Survey Global Change Research Program. They're doing what they've been doing for more than a decade: measuring how the park's storied glaciers are melting.

So far, the results have been positively chilling. When President Taft created Glacier National Park in 1910, it was home to an estimated 150 glaciers. Since then the number has decreased to fewer than 30, and most of those remaining have shrunk in area by two-thirds. Fagre predicts that within 30 years most if not all of the park's namesake glaciers will disappear.

"Things that normally happen in geologic time are happening during the span of a human lifetime," says Fagre. "It's like watching the Statue of Liberty melt."

Scientists who assess the planet's health see indisputable evidence that Earth has been getting warmer, in some cases rapidly. Most believe that human activity, in particular the burning of fossil fuels and the resulting buildup of greenhouse gases in the atmosphere, have influenced this warming trend. In the past decade scientists have documented record-high average annual surface temperatures and have been observing other signs of change all over the planet: in the distribution of ice, and in the salinity, levels, and temperatures of the oceans.

"This glacier used to be closer," Fagre declares as we crest a steep section, his glasses fogged from exertion. He's only half joking. A trailside sign notes that since 1901, Sperry Glacier has shrunk from more than 800 acres (320 hectares) to 300 acres (120 hectares). "That's out of date," Fagre says, stopping to catch his breath. "It's now less than 250 acres (100 hectares)."

Everywhere on Earth ice is changing. The famed snows of Kilimanjaro have melted more than 80 percent since 1912. Glaciers in the Garhwal Himalaya in India are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035. Arctic sea ice has thinned significantly over the past half century, and its extent has declined by about 10 percent in the past 30 years. NASA's repeated laser altimeter readings show the edges of Greenland's ice sheet shrinking. Spring freshwater ice breakup in the Northern Hemisphere now occurs nine days earlier than it did 150 years ago, and autumn freeze-up ten days later. Thawing permafrost has caused the ground to subside more than 15 feet (4.6 meters) in parts of Alaska. From the Arctic to Peru, from Switzerland to the equatorial glaciers of Man Jaya in Indonesia, massive ice fields, monstrous glaciers, and sea ice are disappearing, fast.

When temperatures rise and ice melts, more water flows to the seas from glaciers and ice caps, and ocean water warms and expands in volume. This combination of effects has played the major role in raising average global sea level between four and eight inches (10 and 20 centimeters) in the past hundred years, according to the Intergovernmental Panel on Climate Change (IPCC).

Scientists point out that sea levels have risen and fallen substantially over Earth's 4.6-billion-year history. But the recent rate of global sea level rise has departed from the average rate of the past two to three thousand years and is rising more rapidly-about one-tenth of an inch a year. A continuation or acceleration of that trend has the potential to cause striking changes in the world's coastlines.

Driving around Louisiana's Gulf Coast, Windell Curole can see the future, and it looks pretty wet. In southern Louisiana coasts are literally sinking by about three feet (a meter) a century, a process called subsidence. A sinking coastline and a rising ocean combine to yield powerful effects. It's like taking the global sea-level-rise problem and moving it along at fast-forward.

The seventh-generation Cajun and manager of the South Lafourche Levee District navigates his truck down an unpaved mound of dirt that separates civilization from inundation, dry land from a swampy horizon. With his French-tinged lilt, Curole points to places where these bayous, swamps, and fishing villages portend a warmer world: his high school girlfriend's house partly submerged, a cemetery with water lapping against the white tombs, his grandfather's former hunting camp now afloat in a stand of skeleton oak snags. "We live in a place of almost land, almost water," says the 52-year-old Curole.

Rising sea level, sinking land, eroding coasts, and temperamental storms are a fact of life for Curole. Even relatively small storm surges in the past two decades have overwhelmed the system of dikes, levees, and pump stations that he manages, upgraded in the 1990s to forestall the Gulf of Mexico's relentless creep. "I've probably ordered more evacuations than any other person in the country," Curole says.

The current trend is consequential not only in coastal Louisiana but around the world. Never before have so many humans lived so close to the coasts: More than a hundred million people worldwide live within three feet (a meter) of mean sea level. Vulnerable to sea-level rise, Tuvalu, a small country in the South Pacific, has already begun formulating evacuation plans. Megacities where human populations have concentrated near coastal plains or river deltas-Shanghai, Bangkok, Jakarta, Tokyo, and New York-are at risk. The projected economic and humanitarian impacts on low-lying, densely populated, and desperately poor countries like Bangladesh are potentially catastrophic. The scenarios are disturbing even in wealthy countries like the Netherlands, with nearly half its landmass already at or below sea level.

Rising sea level produces a cascade of effects. Bruce Douglas, a coastal researcher at Florida International University, calculates that every inch (2.5 centimeters) of sea-level rise could result in eight feet (2.4 meters) of horizontal retreat of sandy beach shorelines due to erosion. Furthermore, when salt water intrudes into freshwater aquifers, it threatens sources of drinking water and makes raising crops problematic. In the Nile Delta, where many of Egypt's crops are cultivated, widespread erosion and saltwater intrusion would be disastrous since the country contains little other arable land.

In some places marvels of human engineering worsen effects from rising seas in a warming world. The system of channels and levees along the Mississippi effectively stopped the millennia-old natural process of rebuilding the river delta with rich sediment deposits. In the 1930s oil and gas companies began to dredge shipping and exploratory canals, tearing up the marshland buffers that helped dissipate tidal surges. Energy drilling removed vast quantities of subsurface liquid, which studies suggest increased the rate at which the land is sinking. Now Louisiana is losing approximately 25 square miles (65 square kilometers) of wetlands every year, and the state is lobbying for federal money to help replace the upstream sediments that are the delta's lifeblood.

Local projects like that might not do much good in the very long run, though, depending on the course of change elsewhere on the planet. Part of Antarctica's Larsen Ice Shelf broke apart in early 2002. Although floating ice does not change sea level when it melts (any more than a glass of water will overflow when the ice cubes in it melt), scientists became concerned that the collapse could foreshadow the breakup of other ice shelves in Antarctica and allow increased glacial discharge into the sea from ice sheets on the continent. If the West Antarctic ice sheet were to break up, which scientists consider very unlikely this century, it alone contains enough ice to raise sea level by nearly 20 feet (6 meters).

Even without such a major event, the IPCC projected in its 2001 report that sea level will rise anywhere between 4 and 35 inches (10 and 89 centimeters) by the end of the century. The high end of that projection-nearly three feet (a meter)-would be "an unmitigated disaster," according to Douglas.

Down on the bayou, all of those predictions make Windell Curole shudder. "We're the guinea pigs," he says, surveying his aqueous world from the relatively lofty vantage point of a 12-foot-high (3.7-meter) earthen berm. "I don't think anybody down here looks at the sea-level-rise problem and puts their heads in the sand." That's because soon there may not be much sand left.

Rising sea level is not the only change Earth's oceans are undergoing. The ten-year-long World Ocean Circulation Experiment, launched in 1990, has helped researchers to better understand what is now called the ocean conveyor belt.

Oceans, in effect, mimic some functions of the human circulatory system. Just as arteries carry oxygenated blood from the heart to the extremities, and veins return blood to be replenished with oxygen, oceans provide life-sustaining circulation to the planet. Propelled mainly by prevailing winds and differences in water density, which changes with the temperature and salinity of the seawater, ocean currents are critical in cooling, warming, and watering the planet's terrestrial surfaces-and in transferring heat from the Equator to the Poles.

The engine running the conveyor belt is the density-driven thermohaline circulation ("thermo" for heat and "haline" for salt). Warm, salty water flows from the tropical Atlantic north toward the Pole in surface currents like the Gulf Stream. This saline water loses heat to the air as it is carried to the far reaches of the North Atlantic. The coldness and high salinity together make the water more dense, and it sinks deep into the ocean. Surface water moves in to replace it. The deep, cold water flows into the South Atlantic, Indian, and Pacific Oceans, eventually mixing again with warm water and rising back to the surface.

Changes in water temperature and salinity, depending on how drastic they are, might have considerable effects on the ocean conveyor belt. Ocean temperatures are rising in all ocean basins and at much deeper depths than previously thought, say scientists at the National Oceanic and Atmospheric Administration (NOAA). Arguably, the largest oceanic change ever measured in the era of modern instruments is in the declining salinity of the subpolar seas bordering the North Atlantic.

Robert Gagosian, president and director of the Woods Hole Oceanographic Institution, believes that oceans hold the key to potential dramatic shifts in the Earth's climate. He warns that too much change in ocean temperature and salinity could disrupt the North Atlantic thermohaline circulation enough to slow down or possibly halt the conveyor belt-causing drastic climate changes in time spans as short as a decade.

The future breakdown of the thermohaline circulation remains a disturbing, if remote, possibility. But the link between changing atmospheric chemistry and the changing oceans is indisputable, says Nicholas Bates, a principal investigator for the Bermuda Atlantic Time-series Study station, which monitors the temperature, chemical composition, and salinity of deep-ocean water in the Sargasso Sea southeast of the Bermuda Triangle.

Oceans are important sinks, or absorption centers, for carbon dioxide, and take up about a third of human-generated CO2. Data from the Bermuda monitoring programs show that CO2 levels at the ocean surface are rising at about the same rate as atmospheric CO2. But it is in the deeper levels where Bates has observed even greater change. In the waters between 820 and 1,476 feet (250 and 450 meters) deep, CO2 levels are rising at nearly twice the rate as in the surface waters. "It's not a belief system; it's an observable scientific fact," Bates says. "And it shouldn't be doing that unless something fundamental has changed in this part of the ocean."

While scientists like Bates monitor changes in the oceans, others evaluate CO2 levels in the atmosphere. In Vestmannaeyjar, Iceland, a lighthouse attendant opens a large silver suitcase that looks like something out of a James Bond movie, telescopes out an attached 15-foot (4.5-meter) rod, and flips a switch, activating a computer that controls several motors, valves, and stopcocks. Two two-and-a-half liter (about 26 quarts) flasks in the suitcase fill with ambient air. In North Africa, an Algerian monk at Assekrem does the same. Around the world, collectors like these are monitoring the cocoon of gases that compose our atmosphere and permit life as we know it to persist.

When the weekly collection is done, all the flasks are sent to Boulder, Colorado. There, Pieter Tans, a Dutch-born atmospheric scientist with NOAA's Climate Monitoring and Diagnostics Laboratory, oversees a slew of sensitive instruments that test the air in the flasks for its chemical composition. In this way Tans helps assess the state of the world's atmosphere.

By all accounts it has changed significantly in the past 150 years.

Walking through the various labs filled with cylinders of standardized gas mixtures, absolute manometers, and gas chromatographs, Tans offers up a short history of atmospheric monitoring. In the late 1950s a researcher named Charles Keeling began measuring CO2 in the atmosphere above Hawaii's 13,679-foot (4,169-meter) Mauna Loa. The first thing that caught Keeling's eye was how CO2 level rose and fell seasonally. That made sense since, during spring and summer, plants take in CO2 during photosynthesis and produce oxygen in the atmosphere. In the fall and winter, when plants decay, they release greater quantities of CO2 through respiration and decay. Keeling's vacillating seasonal curve became famous as a visual representation of the Earth "breathing."

Something else about the way the Earth was breathing attracted Keeling's attention. He watched as CO2 level not only fluctuated seasonally, but also rose year after year. Carbon dioxide level has climbed from about 315 parts per million (ppm) from Keeling's first readings in 1958 to more than 375 ppm today. A primary source for this rise is indisputable: humans' prodigious burning of carbon-laden fossil fuels for their factories, homes, and cars.

Tans shows me a graph depicting levels of three key greenhouse gases-CO2, methane, and nitrous oxide-from the year 1000 to the present. The three gases together help keep Earth, which would otherwise be an inhospitably cold orbiting rock, temperate by orchestrating an intricate dance between the radiation of heat from Earth back to space (cooling the planet) and the absorption of radiation in the atmosphere (trapping it near the surface and thus warming the planet).

Tans and most other scientists believe that greenhouse gases are at the root of our changing climate. "These gases are a climate-change driver," says Tans, poking his graph definitively with his index finger. The three lines on the graph follow almost identical patterns: basically flat until the mid-1800s, then all three move upward in a trend that turns even more sharply upward after 1950. "This is what we did," says Tans, pointing to the parallel spikes. "We have very significantly changed the atmospheric concentration of these gases. We know their radiative properties," he says. "It is inconceivable to me that the increase would not have a significant effect on climate."

Exactly how large that effect might be on the planet's health and respiratory system will continue to be a subject of great scientific and political debate-especially if the lines on the graph continue their upward trajectory.

Eugene Brower, an Inupiat Eskimo and president of the Barrow Whaling Captains' Association, doesn't need fancy parts-per-million measurements of CO2 concentrations or long-term sea-level gauges to tell him that his world is changing.

"It's happening as we speak," the 56-year-old Brower says as we drive around his home in Barrow, Alaska-the United States' northernmost city-on a late August day. In his fire chief's truck, Brower takes me to his family's traditional ice cellars, painstakingly dug into the permafrost, and points out how his stores of muktuk-whale skin and blubber recently began spoiling in the fall because melting water drips down to his food stores. Our next stop is the old Bureau of Indian Affairs school building. The once impenetrable permafrost that kept the foundation solid has bucked and heaved so much that walking through the school is almost like walking down the halls of an amusement park fun house. We head to the eroding beach and gaze out over open water. "Normally by now the ice would be coming in," Brower says, scrunching up his eyes and scanning the blue horizon.

We continue our tour. Barrow looks like a coastal community under siege. The ramshackle conglomeration of weather-beaten houses along the seaside gravel road stands protected from fall storm surges by miles-long berms of gravel and mud that block views of migrating gray whales. Yellow bulldozers and graders patrol the coast like sentries.

The Inupiat language has words that describe many kinds of ice. Piqaluyak is salt-free multiyear sea ice. Ivuniq is a pressure ridge. Sarri is the word for pack ice, tuvaqtaq is bottom-fast ice, and shore-fast ice is tuvaq. For Brower, these words are the currency of hunters who must know and follow ice patterns to track bearded seals, walruses, and bowhead whales.

There are no words, though, to describe how much, and how fast, the ice is changing. Researchers long ago predicted that the most visible impacts from a globally warmer world would occur first at high latitudes: rising air and sea temperatures, earlier snowmelt, later ice freeze-up, reductions in sea ice, thawing permafrost, more erosion, increases in storm intensity. Now all those impacts have been documented in Alaska. "The changes observed here provide an early warning system for the rest of the planet," says Amanda Lynch, an Australian researcher who is the principal investigator on a project that works with Barrow's residents to help them incorporate scientific data into management decisions for the city's threatened infrastructure.

Before leaving the Arctic, I drive to Point Barrow alone. There, at the tip of Alaska, roughshod hunting shacks dot the spit of land that marks the dividing line between the Chukchi and Beaufort Seas. Next to one shack someone has planted three eight-foot (2.4-meter) sticks of white driftwood in the sand, then crisscrossed their tops with whale baleen, a horny substance that whales of the same name use to filter life-sustaining plankton out of seawater. The baleen, curiously, looks like palm fronds.

So there, on the North Slope of Alaska, stand three makeshift palm trees. Perhaps they are no more than an elaborate Inupiat joke, but these Arctic palms seem an enigmatic metaphor for the Earth's future.

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As the climate warms, how much, and how quickly, will Earth's glaciers melt?

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Destructive flooding hit Venice, Italy on November 12, when the second highest water level on record--1.87 meters (6.2 feet)--inundated over 80% of the historic city at 10:50 pm local time. At least two deaths are being blamed on the flood, and damage will be in the hundreds of millions of dollars, said Venice's mayor. Venice's iconic Saint Mark's Square was inundated by more than one meter of water, while the adjacent Saint Mark's Basilica was flooded for the only the sixth time in 1200 years. Four of these six floods have occurred in the past twenty years, according to Reuters. A new storm on Friday, November 15, brought the seventh highest water level on record to Venice: 1.54 meters (5.1 feet), and another strong storm on Sunday, November 17, brought the ninth highest water level on record: 1.50 meters (4.9'). Modern record-keeping extends back to 1897 for the city.

Causes of the acqua alta: wind, rainfall runoff, and full moon tides

The main cause of Venice's flood was the counter-clockwise flow of air around a strong low-pressure system centered off the southwest coast of Italy. The low brought strong winds in excess of 30 knots (34.5 mph) that blew from south to north, nearly parallel to the axis of the Adriatic Sea. The winds forced a large storm surge into Venice, which lies at the north end of the Adriatic (Figure 1.) The flooding was exacerbated by pre-existing high-water levels in Venice's lagoon, due to periodic rains that have affected Venice since early November, plus additional heavy rains from the November 12 storm. November 12 was also the date of the full moon, which brought some of the highest tides of the year.

Venice is notorious for these "acqua alta" (high water) events, which periodically flood the renowned St. Mark's Square-the lowest part of the city-as well as many of the city's waterfront businesses and sidewalks. As explained by Bob Henson at the Category 6 blog after Venice's October 2018 acqua alta event, the phenomenon occurs when water is pushed lengthwise from south to north across the Adriatic Sea, parallel to Italy's east coast. The water naturally sloshes back and forth in the Adriatic over a 22-hour cycle called a seiche. When the seiche happens to slosh into Venice at high tide, it can cause significant flooding during strong storms. Acqua alta events are most common in autumn and winter, when astronomical tides are at their highest.

Storm tides in Venice are classified as "exceptional" when they exceed 140 cm (55.1"), which is enough to flood 50% of the city. According to City of Venice records, exceptional storm tides have occurred twenty times since the late 1880s: once in the 79-year period from 1872 to 1950 (April 16, 1936); nine times in the 50-year period from 1951 - 2000; and-ominously-twelve times in just the last two decades, including the past week's three events. Here are the top-ten highest acqua alta events on record in Venice:

Venice is sinking and sea level is rising

Flooding in Venice is steadily worsening, since sea level is rising at the same time that the city is sinking. Relative sea level has risen about 25 cm (9.8 in) in Venice in the 100 years ending in 2012. About half of the this was due to human-caused global sea level rise, and the other half from subsidence due to natural and human causes. This included compaction of the soil from centuries of building, plus pumping of fresh water from an aquifer beneath the lagoon between the 1920s and early 1970s. The rate of subsidence slowed down by a factor of four after officials put a stop to ground water pumping.

Additional problems: erosion and lack of sand replenishment

Heightened flooding in Venice has also been occurring in recent decades because the protective salt marshes in the lagoon surrounding the city are steadily eroding--largely due to the fact that 600 years ago, the city diverted the courses of the four major rivers that flowed into the lagoon, forcing them to empty into the ocean directly. This was done so that sediments would not build up and allow hostile armies to approach the city via land. Without new sediments to replenish them, the marshes in the lagoon have been steadily eroding away. Water pollution has also contributed to erosion problems by killing eelgrass, the chief anchor of the salt marshes.

Additional problems have been caused by jetties built at the three entrances to Venice's lagoon to hold back the sea. These jetties act as barriers to the natural inflow of fresh sand to replenish beaches in the lagoon, and the sand now accumulates along the jetties. The jetties also act as barriers that disrupt ocean currents and contribute to coastal erosion.

Finally, Venice's lagoon is protected by a number of barrier islands. These islands are steadily eroding, due to construction projects, summer beach crowds, and beach-going vehicles.

A $6.3 billion lagoon defense system is nearing completion

In the wake of the devastating 1966 floods, planning began for a system of inflatable gates that would rise up out of the ocean bed to block incoming storm surges into Venice's three inlets into the Adriatic Sea. In 2003, construction began on the MOSE Project, which was scheduled to be completed in 2012. However cost overruns have tripled the price of MOSE to at least $6.3 billion, and the project has been beset by prolonged delays and corruption--culminating in the arrest and indictment of the mayor of Venice. MOSE is now expected to debut in 2022 at the earliest. "If Mose had been working, then we would have avoided this exceptional high tide," city mayor Luigi Brugnaro Brugnaro said in a Reuters interview.

In theory, the gates and additional coastal defense measures being undertaken will protect Venice against storm surges bringing storm tides of up to 3 meters (9.8'). Lower parts of the city begin flooding at a water level of 0.8 m, and the gates are designed to be closed when water levels exceed 1.1 m (3.6')-enough to flood 14% of the city. However, multiple studies have found that if sea level rises 0.5 m (1.6'), the gates would allow considerable flooding of Venice, since water would find new entry points into the Venice lagoon to the north and south, and leak through the gates. Furthermore, the gates do nothing to reduce the incidence of nuisance flooding--when ordinary high tides combined with heavy rains flood less than 12% of the city. With some climate scientists warning that Earth could see sea level rise 0.5 m by 2050 - 2080, the MOSE gates may have to close every day and open only at the time of low tide just a few decades after they go into service. Operation of the gates in this manner would trap pollutants in the lagoon and adversely affect the ecosystem--and greatly restrict boat traffic through the gate locks. Considering that it has already taken more than 50 years from the initial planning stages to get the current MOSE system nearly ready, Venice needs to start planning now for how it will manage sea level rise when MOSE is obsolete 50 or so years from now.

They'd best learn from their mistakes. In a 2017 investigative report, "Venice and MOSE: story of a failure," the Italian newspaper La Stampa found that the 36-ton hinges that connect the gates to their concrete housing were in an advanced state of corrosion after spending years underwater, and were at an extremely high risk of being unusable. Yale's Environment 360 website has an excellent feature on the MOSE project by Jeff Goodell-author of the must-read 2017 book, The Water Will Come: Rising Seas, Sinking Cities, and the Remaking of the Civilized World. I reviewed the book in 2017.

Andrew Freedman of the Capital Weather Gang has an excellent photo essay of this week's flooding in Venice.

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Destructive flooding hit Venice, Italy on November 12, when the second highest water level on record--1.87 meters (6.2 feet)--inundated over 80% of the historic city at 10:50 pm local time. At least two deaths are being blamed on the flood, and damage will be in the hundreds of millions of dollars, said Venice's mayor.

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As temperatures rise and the air becomes warmer, more moisture evaporates from land and water into the atmosphere. More moisture in the air generally means we can expect more rain and snow (called precipitation) and more heavy downpours. But this extra precipitation is not spread evenly around the globe, and some places might actually get less precipitation than they used to get. That's because climate change causes shifts in air and ocean currents, which can change weather patterns.

What's happening now?

On average, the world is already getting more precipitation now than it did 100 years ago: 6 percent more in the United States and nearly 2 percent more worldwide.

The effects vary by region, though. For example, states in the Northeast are getting more precipitation than they used to get, but Hawaii is getting less.

What will happen in the future?

Precipitation is expected to increase in higher latitudes and decrease in areas closer to the Equator. The northern United States will become wetter while the South, particularly the Southwest, will become drier.

Why does it matter?

Too little or too much water can be a problem. In many places, people depend on rain and snowmelt to fill lakes and streams and provide a source of water for drinking, watering crops, and other uses. However, heavy rain can cause flooding.

Check out the major effects of changing rain and snow patterns on people and the environment:

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Changing Rain and Show Patterns | A Student's Guide to Global Climate Change | US EPA

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As temperatures rise and the air becomes warmer, more moisture evaporates from land and water into the atmosphere. More moisture in the air generally means we can expect more rain and snow (called precipitation) and more heavy downpours. But this extra precipitation is not spread evenly around the globe, and some places might actually get less precipitation than they used to get.

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Tropical cyclones in the northwestern Pacific have strengthened about 10 percent since the 1970s because of warming ocean temperatures, researchers report this week in Science Advances. According to an extensive analysis of historical cyclone data, nearly 65 percent of typhoons now reach category 3 or higher on the Saffir-Simpson scale, compared with around 45 percent just decades ago.

The northwestern Pacific produces some of the world's most intense and most devastating tropical cyclones, called typhoons in the Pacific and hurricanes in the Atlantic. The category 5 super typhoon Haiyan, for instance, had record winds that reached nearly 200 miles per hour, and the 2013 storm killed at least 6,300 people in the Philippines.

"It is important to understand what controls typhoon intensity and to predict how it will change," says lead study author Wei Mei of the Scripps Institute of Oceanography.

For years scientists have been working to determine how climate change is affecting these storms. Warmer waters should make for more intense storms in theory, but plenty of other factors can affect tropical cyclone development. This year's Atlantic hurricane season, for instance, should be below normal in part because of El Niño, according to the most recent forecast from the National Oceanic and Atmospheric Administration. Such variability has made finding a signal from climate change difficult.

In the new study, Mei's team looked at the average intensity of tropical cyclones that occurred in the northwestern Pacific between 1951 and 2010. They focused on storms that reached at least category 1 on the Saffir-Simpson scale and examined season-to-season variability, of which there was quite a bit. Some seasons saw much stronger storms on average than others, others much weaker. Plotted out over the years, though, the average intensity could be seen starting to rise in the 1970s.

But what is causing that rise? The team considered several factors that influence tropical cyclones, such as air pressure, sea surface temperatures and localized differences in wind speed and direction, known as wind shear. They were surprised to find that the variability in ocean temperatures, rather than atmospheric conditions, were dominant in controlling the observed changes in typhoon intensity, Mei says.

"How strongly and quickly a cyclone can grow depends on two oceanic factors: pre-storm sea surface temperature and the difference in temperature between the surface and subsurface," Mei explains. "A warmer sea surface generally provides more energy for storm development and thus favors more intense typhoons. A large change in temperature from the surface to subsurface, however, can disrupt this flow of energy, because strong winds drive turbulence in the upper ocean, bringing cold water up from below and thereby cooling the sea surface."

Since the mid-1970s, sea-surface temperatures in the tropical northwestern Pacific have risen by about 1 degree Fahrenheit, while temperatures at 250 feet below the surface have gone up by about 1.4 degrees. This reduction in the vertical temperature difference favors more intense typhoons, Mei says.

The researchers project that even under a scenario of moderate warming-one in which there are cutbacks in greenhouse gas emissions-the average typhoon intensity will still increase by another 14 percent by 2100. If emissions continue apace, "we anticipate that the typhoons will intensify even more," Mei says.

There appears to be a trade-off between typhoon number and intensity. A recent study published in Nature Climate Change found that as ocean waters have warmed over the last 30 years, tropical cyclones globally have slightly decreased in number but increased in intensity. And earlier this year, a team led by Mei reported in the Journal of Climate that the number of storms in the northwestern Pacific has declined since the mid-1990s due to rising sea surface temperatures.

But the decline in storm number should not put anyone at ease, Mei notes: "It is the most intense typhoons that cause the most damage."

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Warmer Waters Are Making Pacific Typhoons Stronger

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Tropical cyclones in the northwestern Pacific have strengthened about 10 percent since the 1970s because of warming ocean temperatures, researchers report this week in Science Advances. According to an extensive analysis of historical cyclone data, nearly 65 percent of typhoons now reach category 3 or higher on the Saffir-Simpson scale, compared with around 45 percent just decades ago.

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If you get the feeling lately that whenever it rains, it pours, blame greenhouse gases. Episodes of intense rainfall are happening more frequently, thanks to human emissions of carbon dioxide, a new study suggests. A companion article marks the first time that researchers have pinned the blame for an extended bout of flooding-the inundations that swamped parts of the United Kingdom in autumn 2000-on those planet-warming gases.

In October and November 2000, floods soaked large swaths of England and Wales, damaging almost 10,000 homes and businesses and causing losses estimated to exceed $2 billion. Lacking hard data, scientists are loath to assign blame for this flood or any weather event to climate change. Now, however, research reported in online today in Nature suggests that human-caused climate change, brought about by past emissions of carbon dioxide, almost certainly boosted the risk of those floods.

To determine how rising temperatures have altered flood risk, atmospheric scientist Pardeep Pall of the University of Oxford in the United Kingdom and his colleagues ran thousands of climate simulations. In roughly half of them, they reduced atmospheric concentrations of carbon dioxide to levels measured in the year 1900, and they adjusted ocean temperatures and the amount of Arctic sea ice-which affects high-latitude weather patterns-accordingly. In the other simulations, they modeled modern conditions. Then they compared the rainfall amounts generated in both types of simulations. Finally, they fed the rainfall values into a model that assesses the potential for flooding.

In 90% of the simulations, results suggested that the flood risk in England and Wales in autumn 2000 was at least 20% higher than it would have been in 1900. In two-thirds of the cases, the flood risk was at least 90% higher-nearly double the risk at the beginning of the 20th century.

Such extremes in precipitation are evident everywhere, says Francis Zwiers, a climate modeler with the government agency Environment Canada in Toronto. In large part, it's simple physics. Warm air can hold more water vapor than cold air. For each 1°C rise in temperature, air can contain about 7% more moisture, which can condense to fall as rain.

In another analysis, also reported online today in Nature , Zwiers and colleagues analyzed meteorological data collected at more than 6000 weather stations in the Northern Hemisphere from 1951 through 1999. By comparing those data with the output of several climate models, the researchers found that warming caused by human emissions of carbon dioxide has boosted the numbers of 1- and 5-day-long episodes of intense precipitation across North America, Eurasia, and India.

Both studies improved on previous work. Zwiers and colleagues compared observational data with results from simulations rather than running a model-to-model comparison. Pall's team performed a large number of simulations and analyzed them statistically.

"Since we first recognized the threat of global warming, scientists have consistently stated that no single extreme weather event can be definitively link to anthropogenic climate change," says Mark Maslin, a climate scientist at the Environment Institute at University College London. The paper by Pall and colleagues "fundamentally changes this," he notes.

Recent floods in Pakistan, Brazil, and Australia were larger and did more damage than the U.K. floods of 2000, Maslin notes. Together, the Nature papers "provide a very strong scientific message to politicians that the occurrence and magnitude of huge floods around the world have been made worse by [human-caused] climate change," he adds. "And there we were thinking all the effects of climate change would be in the far future."

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Rising Temperatures Bringing Bigger Floods

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If you get the feeling lately that whenever it rains, it pours, blame greenhouse gases. Episodes of intense rainfall are happening more frequently, thanks to human emissions of carbon dioxide, a new study suggests.

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Abstract

Floods are considered an annual natural disaster in Kelantan. However, the record-setting flood of 2014 was a 'tsunami-like disaster'. Hospital Universiti Sains Malaysia was the only fully functioning hospital in the state and had to receive and manage cases from the hospitals and clinics throughout Kelantan. The experiences, challenges, and recommendations resulting from this disaster are highlighted from an emergency medicine perspective so that future disaster preparedness is truly a preparation. The history of how the health campus was constructed with the collaboration of Perunding Alam Bina and Perkins and Willis of Chicago is elaborated.

Introduction

Floods are an annual occurrence of varying severities in Kelantan state on the east coast of Peninsular Malaysia. They also affect its neighbouring states, specifically Terengganu and Pahang. Previous floods, including those of 1927 and 1967, were considered significant in Kelantan's history. The 1967 flood had a major impact on the Kelantan population; it has been estimated that 70% of the kampungs (villages) in Kelantan, or nearly half of the state's population, were affected ( 1). The 2014 flood was the most significant and largest recorded flood in the history of Kelantan. It was considered to be a "tsunami-like disaster" in which 202,000 victims were displaced ( 2). This flood was called 'Bah Kuning' (yellow-coloured flood) because of its high mud content ( 3, 4).

Chronology of the Flood

Torrential rains that began on the 17th of December, 2014, led to flash flooding and forced 3390 people in Kuala Krai, Kelantan, to flee their homes ( 5). Later, three days of continuous heavy rain fell from the 21st to the 23rd of December, 2014, in Gua Musang. This was a record-setting rainfall of 1 295 mm, equivalent to the amount of rain usually seen in a span of 64 days. As a result, the water levels of three major rivers, the Sungai Galas in Dabong, the Sungai Lebir in Tualang and the Sungai Kelantan, rose drastically above the water levels considered dangerous ( 6).

The highest recorded level of the Sungai Galas in Dabong, GuaMusang was 46.47 metres (danger level: 38 metres), the highest recorded level of the Sungai Lebir in Tualang, Kuala Krai was 42.17 metres (danger level: 35 metres), and the highest recorded level of the Sungai Kelantan was 34.17 metres at Tangga Krai, Kuala Krai (danger level: 25 metres) and 22.74 metres (danger level: 16 metres) at the Guillemard Bridge in Tanah Merah. The highest level of the Sungai Golok at Rantau Panjang was 10.84 metres, which was over the danger level of nine metres ( 7) ().

Emergency Medicine Experiences and Challenges

Disaster medicine (DM) is a medical specialty, meaning that any medical doctor can pursue it. However, emergency physicians (EPs) are often required to play key roles in disaster management ( 8). The most important topics in this specialty include disaster mitigation and preparation, as well as the creation of a properly designed and effective disaster response and recovery plan. This is essential to minimising physical and psychosocial casualties.

Unlike other flood disasters that had many casualties ( 9) and deployments of medical relief teams, 'Bah Kuning' in Kelantan resulted in minimal casualties, with only 13 deaths recorded ( 7), and no relief teams were deployed from Hospital Universiti Sains Malaysia (HUSM). However, there was a surge of patients at HUSM due to the closure of a nearby hospital, Hospital Raja Perempuan Zainab 2 (HRPZ2). In fact, the only available tertiary centre for all of Kelantan was HUSM ( 10). There was an influx of patients who presented to HUSM after HRPZ2 closed on the 25th of December, 2014. Those cases were generally acute problems from underlying chronic medical conditions such as acute coronary syndrome, acute exacerbation of chronic obstructive airway disease, heart failure, sepsis, and other diseases. displays the number of cases that presented to the ED at HUSM during the disaster. The average number of cases that presented to the Emergency Department (ED) at HUSM was 180 cases/day. Although the number was not as high as most government hospitals, patients who presented to the ED at HUSM were managed effectively. Most of the procedures were performed by ED residents, including bedside ultrasounds, central line insertions, and chest tube insertions, until diagnoses were confirmed or patients were stable. Access block became an issue because all referral cases must be reviewed in the ED by their receiving departments and because it was not uncommon for beds to be unavailable. Some of the patients were managed in ED for more than 24 hours. These patients had to be monitored and reviewed regularly, particularly those in the red zone.

Table 1:

Another challenge that was encountered during the disaster was a shortage of staff. Almost 50% of the staff was affected by the floods, including the head of the Emergency Department. Furthermore, there was no disaster declaration from the top-down at HUSM on day 1 of the disaster, meaning that the ED staff had to handle the situation themselves. With the increasing number of patients, this became a disaster for them. Luckily,a group of medical students was proactive in assisting the staff and managing the triage counter, clerking patients in the green zone and controlling the crowd in the waiting area (10). Their services during the event were commendable, and many of the staffs in ED were taken aback by their initiative.

HUSM also received patients who were transferred by helicopter. The medical evacuation (medevac) involved 137 cases from district hospitals and clinics (Pejabat Kesihatan Daerah) (). Most of the patients were critically ill and required ventilator support. Five cases were transferred direct to Hospital Besut in Terengganu for continuation of critical care because the critical care units at HUSM were fully occupied. Hospital Kuala Krai had the largest number of patients being medevac.

Table 2:

Volunteers began to arrive in Kelantan on the 28th of December, 2014. Most of the volunteers were healthcare providers from universities and the Ministry of Health. A total of 261 volunteers registered with the Volunteer Operations Office (Bilik Gerakan Banjir Sukarelawan HUSM) to assist with the administration of healthcare services. However, some of them had to go to the district area, along with Jabatan Kesihatan Negeri (JKN) Kelantan and MERCY Malaysia. displays the total number of volunteers and their affiliations. Coordinating the volunteers with all of the departments in HUSM and JKN Kelantan was also a challenge during the disaster.

Table 3:

Recommendations

Medical management during any disaster must be coordinated by the individuals or organisations most experienced and knowledgeable in disaster management and should not be based solely on the most senior person in an organisation. In our recent experience during the worst recorded flood disaster in our country, both the out-of-hospital and in-hospital disaster responses had to be activated due to the phenomenal scale of the flooding because it affected more than half of the city and state area. Regardless of the nature of the disaster, its management must involve four phases: mitigation/prevention, preparedness, response and recovery. These phases must be well coordinated across all relevant agencies, including those in both health and non-health sectors, so that all of the activities taking place are synchronised across all of the stakeholders involved.

Disaster preparedness is the crux of flood disaster management. Recommendations from an emergency medicine perspective include the following:

* A proper flood disaster preparedness plan and training for it are important not only for emergency medicine residents but also for those working in administration. Administrators who are well versed in disaster will perform disaster management more efficiently. Orders from the top-down will improve coordination and provide moral support for the staff.

* Standard operating procedures (SOPs) need to be kept in writing for various levels of the disaster response, i.e., from the activation of it to the post-disaster phase. These SOPs must be tested and drilled with all personnel involved at regular intervals. Drill outcomes must have measurable parameters for the institution's continued development.

* An effective communication system is of paramount to the coordination of rescue and relief operations. In the present flood disaster, the main network was disrupted extensively in almost all of the district's hospitals. Thus, it is crucial to establish an alternative communication system to handle such emergencies efficiently and effectively. The chain of command within this communication system should be tested from time to time.

* Disaster management is a multidisciplinary activity involving all departments in the hospital. All of the departments should be actively involved in managing cases. Teamwork and flexibility between departments are essential.

* If an overflow of patients occurs at the ER, all of the green zone cases should be diverted to a designated area so that more critical cases (yellow zone and red zone cases) can be managed with the appropriate standard of care. Green zone cases should be relocated to a different area so that the ER is not crowded by patients and their relatives. Using a separate disaster tent will help to control the crowd so that cases can be managed properly. These detached facilities are also important as isolation areas, especially when managing infectious disease cases.

* HUSM received a large number of patients who were transported by helicopters over the five days of the disaster. SOPs should be written to direct the flow of such patients from the helipad to the ER.

* During any disaster, a sudden influx of both healthcare and non-healthcare volunteer workers should be expected. Protocols need to be in place to manage and coordinate these volunteers so that manpower specialties are channelled to specific areas in the best possible way. This is also true of managing incoming medical equipment and drugs during a disaster.

* Effective human resources management is essential to ensuring adequate staff capacity and continuity of operations during a disaster. Hospital staff contact lists should be regularly updated. Ensuring adequate staff for shift rotations and caring for their welfare aids in supporting morale and reducing medical errors.

* Flood-prone areas and supply roads should be mapped manually or using geographical information systems with overlying existing healthcare facilities to identify unaffected areas and clinics/hospitals. This is important for placing pre-planned medical equipment at strategic sites for swift mobilisation to flooded areas.

Because no one can guarantee that the record-setting flood of 2014 will not recur in 2015 or thereafter, disaster mitigation and preparedness are without a doubt the best way forward.

How a Plan to Build a Medical Campus in Kelantan 35 years ago saved nearly 2000 patients

The initial year (1979-1980) of planning for the USM campus in Kubang Kerian was not without problems, as approvals for the scope of work and the appointment of building consultants (involving two failed negotiations) by the relevant authorities took time. Approval for the scope of work from the JPPN (National Committee for Planning & Development) was received in August 1980, which included an allocation for a 1200-bed HUSM. In September 1980, a special committee chaired by the Chief Secretary (KSN) made the decision to invite five local architectural firms with international partnerships to submit technical and financial proposals. Then, in November 1980, approval was received for the appointment of Perunding Alam Bina (PAB) in collaboration with Perkins and Wills of Chicago (the second top healthcare designer in the US at that time).

With this appointment, two working sessions were held with the consultants in December 1980 and January 1981 to develop an integrated, functional building to reflect the academic programme with consideration for the site's weather conditions. Their "fast track approach" goal for completion of the entire project was May 1985. As the project was about to be launched, the economic recession set in, necessitating rescheduling and repackaging of the project's implementation. Cost-cutting was required; the specific changes included a reduction of the 18-foot bund around the campus to 16 feet (which is still above the level of the record floods of 1927) (). The two floors above the Operating Theatre Complex (designed to accommodate four surgical-based wards) were also removed from the project though the piling work was designed for four floors ( 11).

References

1. Chan NW. Flood disaster management in Malaysia: an evaluation of the effectiveness of government resettlement schemes. [ Disaster Prevention and Management. 1995;4(4):22-29. Google Scholar]

8. Franc JM, Nichols D, Dong SL. Increasing emergency medicine residents' confidence in disaster management: use of an emergency department simulator and an expedited curriculum. [ Prehospital Disaster Med. 2012;27(1):31-35. doi: 10.1017/S1049023X11006807 . [ PubMed] Google Scholar]

11. Baharuddin A, Low SDN, Perunding Alam Bina Perkins & Will International Ltd, Jurutera Konsultant (S.E.A) Sdn Bhd . Malaysia (MY): Perunding Alam Bina, Perkins & Will International Ltd, Jurutera Konsultant (S.E.A) Sdn Bhd; 1981. Master Plan Report School of Medical Sciences The Universiti sains Malaysia Kota Bharu, Kelantan; p. 77. [ Google Scholar]

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The Record-Setting Flood of 2014 in Kelantan: Challenges and Recommendations from an Emergency Medicine Perspective and Why the Medical Campus Stood Dry

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Floods are considered an annual natural disaster in Kelantan. However, the record-setting flood of 2014 was a 'tsunami-like disaster'. Hospital Universiti Sains Malaysia was the only fully functioning hospital in the state and had to receive and manage cases from the hospitals and clinics throughout Kelantan.

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As our climate warms, we're experiencing stronger winds, higher storm surges and record rainfalls during hurricane season - which is also why these storms are becoming more destructive and costly.

Warmer oceans fuel storms

So why do hurricanes bring more rain in a warmer climate?

Evaporation intensifies as temperatures rise, and so does the transfer of heat from the oceans to the air. As the storms travel across warm oceans, they pull in more water vapor and heat.

That means stronger wind, heavier rainfall and more flooding when the storms hit land.

Sea level rise makes storm surges worse

Storm surge happens when waters rise above their normal levels and are pushed inland by wind.

With Hurricane Katrina, it was the storm surge that caused the levees to fail, leading to destruction in the New Orleans area.

Storm surge was also responsible for an extra $2 billion in damage to New York City after Sandy hit in 2012, according to a Rand report.

This phenomenon is made worse by sea level rise, which is triggered by human-caused global warming as warmer ocean water expands and land ice melts.

The average global sea level has already risen by half a foot since 1900 - nearly four of those inches since 1970 - as countries have developed and populations have grown. Higher sea level can push more water inland during hurricane-related storm surges.

Hurricanes are stronger, intensify faster

Stronger hurricanes are becoming more common in a warmer climate.

Researchers suggest that the most damaging U.S. hurricanes are three times more frequent than 100 years ago, and that the proportion of major hurricanes (Category 3 or above) in the Atlantic Ocean has doubled since 1980.

How fast hurricanes intensify has also increased in the Atlantic since the 1980s, due to climate change. Hurricanes Laura and Dorian are prime examples. Both rapidly intensified close to landfall, making it harder to predict the potential danger.

At the same time, hurricanes are moving more slowly, making more damage possible. Scientists are still debating exactly how this drop in speed is linked to climate change, but here's the leading theory: The winds that steer hurricanes move more slowly in a warmer climate.

The damage we've seen from catastrophic hurricanes in recent years shows we need science more than ever to help us prepare for - and act on - climate change.

Act when it matters most

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How climate change makes hurricanes more destructive

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As our climate warms, we're experiencing stronger winds, higher storm surges and record rainfalls during hurricane season - which is also why these storms are becoming more destructive and costly. So why do hurricanes bring more rain in a warmer climate? Evaporation intensifies as temperatures rise, and so does the transfer of heat from the oceans to the air.

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Tropical cyclones in the northwestern Pacific have strengthened about 10 percent since the 1970s because of warming ocean temperatures, researchers report this week in Science Advances. According to an extensive analysis of historical cyclone data, nearly 65 percent of typhoons now reach category 3 or higher on the Saffir-Simpson scale, compared with around 45 percent just decades ago.

The northwestern Pacific produces some of the world's most intense and most devastating tropical cyclones, called typhoons in the Pacific and hurricanes in the Atlantic. The category 5 super typhoon Haiyan, for instance, had record winds that reached nearly 200 miles per hour, and the 2013 storm killed at least 6,300 people in the Philippines.

"It is important to understand what controls typhoon intensity and to predict how it will change," says lead study author Wei Mei of the Scripps Institute of Oceanography.

For years scientists have been working to determine how climate change is affecting these storms. Warmer waters should make for more intense storms in theory, but plenty of other factors can affect tropical cyclone development. This year's Atlantic hurricane season, for instance, should be below normal in part because of El Niño, according to the most recent forecast from the National Oceanic and Atmospheric Administration. Such variability has made finding a signal from climate change difficult.

In the new study, Mei's team looked at the average intensity of tropical cyclones that occurred in the northwestern Pacific between 1951 and 2010. They focused on storms that reached at least category 1 on the Saffir-Simpson scale and examined season-to-season variability, of which there was quite a bit. Some seasons saw much stronger storms on average than others, others much weaker. Plotted out over the years, though, the average intensity could be seen starting to rise in the 1970s.

But what is causing that rise? The team considered several factors that influence tropical cyclones, such as air pressure, sea surface temperatures and localized differences in wind speed and direction, known as wind shear. They were surprised to find that the variability in ocean temperatures, rather than atmospheric conditions, were dominant in controlling the observed changes in typhoon intensity, Mei says.

"How strongly and quickly a cyclone can grow depends on two oceanic factors: pre-storm sea surface temperature and the difference in temperature between the surface and subsurface," Mei explains. "A warmer sea surface generally provides more energy for storm development and thus favors more intense typhoons. A large change in temperature from the surface to subsurface, however, can disrupt this flow of energy, because strong winds drive turbulence in the upper ocean, bringing cold water up from below and thereby cooling the sea surface."

Since the mid-1970s, sea-surface temperatures in the tropical northwestern Pacific have risen by about 1 degree Fahrenheit, while temperatures at 250 feet below the surface have gone up by about 1.4 degrees. This reduction in the vertical temperature difference favors more intense typhoons, Mei says.

The researchers project that even under a scenario of moderate warming-one in which there are cutbacks in greenhouse gas emissions-the average typhoon intensity will still increase by another 14 percent by 2100. If emissions continue apace, "we anticipate that the typhoons will intensify even more," Mei says.

There appears to be a trade-off between typhoon number and intensity. A recent study published in Nature Climate Change found that as ocean waters have warmed over the last 30 years, tropical cyclones globally have slightly decreased in number but increased in intensity. And earlier this year, a team led by Mei reported in the Journal of Climate that the number of storms in the northwestern Pacific has declined since the mid-1990s due to rising sea surface temperatures.

But the decline in storm number should not put anyone at ease, Mei notes: "It is the most intense typhoons that cause the most damage."

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Warmer Waters Are Making Pacific Typhoons Stronger

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Tropical cyclones in the northwestern Pacific have strengthened about 10 percent since the 1970s because of warming ocean temperatures, researchers report this week in Science Advances. According to an extensive analysis of historical cyclone data, nearly 65 percent of typhoons now reach category 3 or higher on the Saffir-Simpson scale, compared with around 45 percent just decades ago.

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Why deforestation is making flooding more common - Deadline News

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Deforestation has had, and continues to have, a dramatic ecological impact. And a significant amount of this impact has been traced to flooding. In light of the devastating floods that have wrought havoc across the Americas in recent weeks, this relationship between deforestation and flooding has been brought into sharper focus.

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The torrents of water that raged down onto this city, killing hundreds of people, are testimony to a man-made ecological disaster. Poverty has transformed Haiti's once-verdant hills into a moonscape of bedrock ravaged by ravines.

More than 98 percent of its forests are gone, leaving no topsoil to hold rains. Even the mango and avocado trees have started to vanish, destroying a vital food source in favor of another necessity for the impoverished - charcoal for cooking.

"The situation will continue, and other catastrophes are foreseeable," Jean-Andre Victor, one of Haiti's top ecologists, said in the capital, Port-au-Prince.

More than 800 are dead across Haiti from floods spawned by Tropical Storm Jeanne over the weekend, with 1,000 more missing and presumed dead. In May, light rains triggered floods that killed more than 3,000 people on Haiti's barren southern border with the Dominican Republic.

"When you remove vegetation, the topsoil washes away. The earth isn't capable of absorbing rainfall," said Rick Perera of the international humanitarian group CARE, which supports alternative energy programs in Haiti to lessen dependence on charcoal.

Less tree cover also means less regular rain, since trees "breathe" water vapor into the air. The result is a dropping water table, making for even poorer farmers, the backbone of Haiti's economy.

A 90-minute flight from Miami, Haiti is one of the poorest countries in the world. Most of its 8 million people don't have jobs, and political instability discourages foreign investors.

U.N. Secretary-General Kofi Annan urged donors on Wednesday to help Haiti recover from the "devastating natural disaster." But it's very much a man-made one.

Most Haitians are descendants of African slaves brought over in the late 1600s by French colonizers who destroyed tens of thousands of acres of virgin forest to plant the cane that made Haiti the world's largest sugar producer. More wood was cut to fuel the sugar mills. Entire forests were shipped to Europe to make furniture of mahogany and dyes from campeachy.

After rebellious slaves defeated Napoleon's army and Haiti became the world's first black republic in 1804, great plantations were divided among the slaves.

Under an inherited French law, land is shared among a man's heirs. One of the fastest growing populations in the world - Haitian women average five births each - has reduced the average holding to little more than a half acre. That's not enough to support a family of seven even in a good rainy season.

Pressed for income, farmers chopped trees to make and sell charcoal.

From the air, you can see the border with the Dominican Republic, which shares Hispaniola island with Haiti. Lush forests stop suddenly and give way to barrenness. Vast stretches of the Dominican Republic remain in the hands of a wealthy few.

The difference in vegetation also is reflected in the death tolls. The Dominican Republic lost just 19 people to Jeanne, including 12 people who drowned in swollen rivers.

In 1950, about 25 percent of Haiti's 10,700 square miles was covered with forest, said Victor, the agronomist. In 1987, it was 10 percent. By 1994, 4 percent. Now, foreign and Haitian scientists find only about 1.4 percent of the Maryland-sized nation is forested, he said.

Here in Gonaives, where rebels launched the rebellion that forced out President Jean-Bertrand Aristide last February, Jeanne deluged the region with rains for some 30 hours. Water-logged valleys behind the mountains funneled torrents of water that bloated the four rivers surrounding the gritty city of 250,000 people.

After the May floods, interim Prime Minister Gerard Latortue, said, "The root of the problem is that we have to go and reforest the hills and until we do that, every two, three, four years after some heavy rain, the same thing could happen again."

Over the past 20 years, the U.S. Agency for International Development has planted 60 million trees in Haiti, but the poor chop down 10 million to 20 million trees each year, said David Adams, USAID director in Haiti.

Perera, the CARE official, said small-scale replanting projects and pilot programs using alternative cooking fuels such as solar energy and propane are trying to change habits. Still, 71 percent of the energy used in Haiti comes from charcoal, Victor said.

Though the deforestation is obvious, many steeped in superstition believe the disasters are caused by a higher power, a belief that officials say makes it hard to fix the problems.

"It was God who made this flood," said Eliphet Joseph, a 43-year-old salesman.

Other people blame decades of official corruption and mismanagement.

"The whole country's environment is messed up, that's why we had these (floods)," said Cherly Etienne, 28, who lost her cousin and aunt.

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The torrents of water that raged down onto this city, killing hundreds of people, are testimony to a man-made ecological disaster. Poverty has transformed Haiti's once-verdant hills into a moonscape of bedrock ravaged by ravines. More than 98 percent of its forests are gone, leaving no topsoil to hold rains.

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Tropical Deforestation and Global Warming

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Tropical deforestation accounts for less than 10 percent of the world's global warming pollution. Protecting forests helps to fight global warming, protect biodiversity, and promote sustainable development.

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Dear EarthTalk: Is it true that cutting and burning trees adds more global warming pollution to the atmosphere than all the cars and trucks in the world combined?- Mitchell Vale, Houston
By most accounts, deforestation in tropical rainforests adds more carbon dioxide to the atmosphere than the sum total of cars and trucks on the world's roads. According to the World Carfree Network (WCN), cars and trucks account for about 14 percent of global carbon emissions, while most analysts attribute upwards of 15 percent to deforestation.

The reason that logging is so bad for the climate is that when trees are felled they release the carbon they are storing into the atmosphere, where it mingles with greenhouse gases from other sources and contributes to global warming accordingly. The upshot is that we should be doing as much to prevent deforestation as we are to increase fuel efficiency and reduce automobile usage.

According to the Environmental Defense Fund (EDF), a leading green group, 32 million acres of tropical rainforest were cut down each year between 2000 and 2009-and the pace of deforestation is only increasing. "Unless we change the present system that rewards forest destruction, forest clearing will put another 200 billion tons of carbon into the atmosphere in coming decades...," says EDF.

"Any realistic plan to reduce global warming pollution sufficiently-and in time-to avoid dangerous consequences must rely in part on preserving tropical forests," reports EDF. But it's hard to convince the poor residents of the Amazon basin and other tropical regions of the world to stop cutting down trees when the forests are still worth more dead than alive. "Conservation costs money, while profits from timber, charcoal, pasture and cropland drive people to cut down forests," adds EDF. Exacerbating global warming isn't the only negative impact of tropical deforestation. It also wipes out biodiversity: More than half of the world's plant and animal species live in tropical rainforests.

One way some tropical countries are reducing deforestation is through participation in the United Nations' Reducing Emissions from Deforestation and Forest Degradation (REDD) program. REDD essentially works to establish incentives for the people who care for the forest to manage it sustainably while still being able to benefit economically. Examples include using less land (and therefore cutting fewer trees) for activities such as coffee growing and meat and milk production. Participating nations can then accrue and sell carbon pollution credits when they can prove they have lowered deforestation below a baseline. The REDD program has channeled over $117 million in direct financial aid and educational support into national deforestation reduction efforts in 44 developing countries across Africa, Asia and Latin America since its 2008 inception.

Brazil is among the countries embracing REDD among other efforts to reduce carbon emissions. Thanks to the program, Brazil has slowed deforestation within its borders by 40 percent since 2008 and is on track to achieve an 80 percent reduction by 2020. Environmentalists are optimistic that the initial success of REDD in Brazil bodes well for reducing deforestation in other parts of the tropics as well.

CONTACTS: WCN, www.worldcarfree.net; EDF, www.edf.org; REDD, www.un-redd.org.

EarthTalk® is written and edited by Roddy Scheer and Doug Moss and is a registered trademark of E - The Environmental Magazine (www.emagazine.com). Send questions to: earthtalk@emagazine.com. Subscribe: www.emagazine.com/subscribe. Free Trial Issue: www.emagazine.com/trial.

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united nations’ reducing emissions from deforestation and forest degradation

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Deforestation and Its Extreme Effect on Global Warming

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Dear EarthTalk: Is it true that cutting and burning trees adds more global warming pollution to the atmosphere than all the cars and trucks in the world combined? - Mitchell Vale, Houston By most accounts, deforestation in tropical rainforests adds more carbon dioxide to the atmosphere than the sum total of cars and trucks on the world's roads.

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Combination approach uses ground-based surveys and satellites to find many more trees than anticipated.

There are roughly 3 trillion trees on Earth - more than seven times the number previously estimated - according to a new tally by an international team of scientists. The study also finds that human activity negatively affects tree abundance from the boreal forests to the equator. Roughly 15 billion trees are cut down each year, the researchers estimate; since the onset of human civilization, the global number of trees has dropped by roughly 46%.

"The scale of human impact is astonishing," says Thomas Crowther, an ecologist at the Netherlands Institute of Ecology in Wageningen who led the study while at Yale University in New Haven, Connecticut. "Obviously we expected humans would have a prominent role, but I didn't expect that it would come out as the as the strongest control on tree density."

The widely accepted previous estimate of the world's tree population, about 400 billion, was based largely on satellite imagery. Though remote imaging reveals a lot about where forests are, it does not provide the resolution of a person counting trunks in a particular plot. Crowther and his colleagues merged these approaches by first gathering data from more than 400,000 ground-based counts reported in forestry inventories and the scientific literature for every continent except Antarctica. These counts allowed them to improve tree-density estimates based on satellite imagery. Then the researchers applied those density estimates areas that lack good ground inventories. For example, ground-truthed data from forests in Canada and northern Europe were used to revise estimates from satellite imagery for similar forests in remote parts of Russia.

"It's not like we discovered new trees," says Crowther. "Rather, we added another layer of information that allowed us to revise much of the previous estimates."

Improved population estimates could help managers weigh the economic benefits that forests provide in terms of water purification, soil conservation and other functions against those of harvesting timber or clearing trees for farmland, says ecosystems services ecologist Becky Chaplin-Kramer of Stanford University in California. "It's great when we can fill in gaps like this," she says.

The highest tree densities, calculated in stems per hectare, were found in the boreal forests of North America, Scandinavia and Russia. These forests are typically tightly packed with skinny conifers and house roughly 749.34 billion trees, 24.28% of the global total. Tropical and subtropical forests, with the greatest area of forested land, are home to 1.29 trillion trees, or 42.82% of the total.

The new numbers raise questions about which species are represented where and how particular forest types evolve, says biogeochemist Susan Trumbore of the Max Planck Institute for Biogeochemistry in Jena, Germany.

The number of trees is just one piece of the puzzle," Trumbore says. "A tree in the tundra is not the same as a tree in the rainforest."

Crowther cautions that even though the new figures do not change the current science on carbon storage or diminish the impact of deforestation. "We're not saying, 'Oh, everything's fine'."

In fact, the work suggests that in some places where one might expect trees to thrive, such as warm regions with lots of moisture, human activities like farming have pushed forest to the margins.

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Global forest survey finds trillions of trees - Nature

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Combination approach uses ground-based surveys and satellites to find many more trees than anticipated. There are roughly 3 trillion trees on Earth - more than seven times the number previously estimated - according to a new tally by an international team of scientists.

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Japan employs underground spaces to ready urban areas for otherwise catastrophic flooding.

Massive underground spaces, such as this one, below the ring roads that run through major residential areas are critical elements of flood control in Tokyo.

Annual rainfall totals have been increasing worldwide in recent years, given the growing frequency of localized torrential rain, typhoons, hurricanes, and other extreme weather phenomena. Not only does the inundation of buildings and underground structures represent a danger to people living in highly developed urban areas in particular, but it also poses a grave threat to urban functions in general. Therefore, developing measures against flood damage is a pressing issue. The Japanese government considers national resilience-including disaster prevention and mitigation, such as flood control-a central element of its policy, and is moving ahead with both public and private initiatives.

Tokyo, one of the world's foremost metropolitan areas, is making use of underground spaces in the fight against flooding. One example is the underground regulating reservoir being constructed to prevent overflow from small and medium-sized rivers. When heavy rain causes a river's water level to rise, water flows from a weir built into a revetment down into the reservoir, thus reducing the amount of water flowing downstream. So far, 28 such facilities have been constructed, collectively holding a total of 2.56 million of water.

Water from a rising river flows into an underground regulating reservoir instead of spilling over the banks of the levee.

One massive reservoir has been built under a major ring road that runs around central Tokyo. When a typhoon dropped record rainfall of up to 32 mm per hour on Tokyo in 2019, the reservoir retained about 490,000 of water, or 90% of its total capacity. Estimates indicate that it lowered water levels downstream by up to 1.5 m. "We have systematically developed river facilities such as this reservoir, which have helped to prevent massive flood damage," says Director ODANAKA, from the Tokyo Metropolitan Government (TMG)'s Bureau of Construction, with conviction. The reservoir is currently undergoing expansion. Eventually, it will be able to compensate for localized heavy rainfall coming down at up to 100 mm per hour.

Shibuya is a popular spot among international tourists. Over 3 million people use the station every day.

Life-saving flood control countermeasures are also being implemented in the area around Shibuya Station, one of Tokyo's most well-known and popular sightseeing spots. Since the land around the station is slightly lower than the surrounding area, the underground malls used to be prone to flooding. However, as part of a massive redevelopment project in the area that is currently underway, a new rainwater storage facility with a capacity of 4,000 was completed underneath the station's east exit, and went into operation in August 2020. It temporarily retains rainwater if the rainfall exceeds a certain amount, and the water drains out through sewer pipes when the weather returns to normal. Director OKUDA, from the TMG's Bureau of Sewerage, said, "Combined with the facility previously built underneath the station's west exit, our storage system can now hold a total of 8,000 of water. Shibuya has evolved into an even safer urban area."

New rainwater retention facilities have been constructed below the Shibuya Station area's underground commercial complexes.

Many other efforts to save lives from flooding are also being made across Japan, including the construction of levees and detention basins, as well as the refinement of heavy rain forecasts. A further example of Japan's inundation prevention measures is the use of dams for hydropower and irrigation to control flooding. To prepare for this year's Olympic and Paralympic Games Tokyo 2020 and beyond, Japan is advancing the development of national land infrastructure that is resilient to natural disasters.

In order to prevent floods in downstream areas when heavy rain is predicted, such as during typhoons, the national and prefectural governments have established a system to discharge a certain amount of dam water in advance.

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Utilizing the City's Underground Spaces to Prevent Flood Damage | The Government of Japan - JapanGov -

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Japan employs underground spaces to ready urban areas for otherwise catastrophic flooding. Massive underground spaces, such as this one, below the ring roads that run through major residential areas are critical elements of flood control in Tokyo. 　Annual rainfall totals have been increasing worldwide in recent years, given the growing frequency of localized torrential rain, typhoons, hurricanes, and other extreme weather phenomena.

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Tim Hutton and Christopher Marsh

Today, many property owners are understandably concerned by the risk and consequences of flooding. This is due to rising awareness of the effects of global warming and to the widespread flooding problems in the winter of 2000-01. People have become especially concerned by the way in which properties that have not been subject to flooding in the past are now at risk. The extent to which this is due to poor management of local drainage and rivers systems, or to climatic change, is outside the scope of this article. However, whatever the cause, the effect on historic buildings must be addressed.

Generally, people in the past were more skilled at positioning structures and managing ground drainage so as to minimise the risk of flooding and water penetration. It is therefore not unusual to find that older buildings in a settlement are situated so as to avoid flooding, and that it is the new developments that are affected - all too often because the new development is on land previously used as water meadows or on flood plains. However, historic buildings still can be affected by flooding and it is useful to identify the causes and risk factors so that cost effective remedial measures can be taken .

Waterfront sites
Historically, many buildings were built next to rivers and streams, in order to use the water for transport or power. Many such structures were expected to be intermittently flooded, and those that have survived often include materials and design features that have allowed them to withstand intermittent flooding relatively unscathed. Warehouses, boathouses and mills are examples of this type of building, and areas such as the waterfront of York are commonly affected. Problems arise when new materials or design features are introduced on refurbishment which do not take account of the likelihood of intermittent flooding. In particular, plasterboard, MDF, electrical systems, service systems, floor claddings and furnishings can often be adversely affecte d .

Coastal sites
Buildings on coastal sites may be affected by the factors described so far and, in addition, they can be flooded due to breaching of sea defences or 'backing up' of floodwater by high tides. A well-known example of this is London, where the Thames Barrage had to be constructed to prevent flooding. Again, older buildings are often constructed to be resistant to the effects of intermittent flooding or have been built on safer sites; and in London few structures built before the mid 19th century are at risk.

Ground drainage
Many individual historic buildings suffer flooding due to defective or poorly managed ground drainage. On a local scale, this is commonly due to rising ground levels and defective street drainage, which may allow local surface water to 'run off' and drain into, rather than out of, ground floor or basement structures. Examples of structures at risk can be found in any town or village and even large high profile buildings can be affected. On a larger scale, mismanagement of the river catchment drainage system by the local authority can result in surface and ground drainage water being 'held back' to create unplanned 'flood plains'. This can occur due to poor maintenance and blocking of drains or culverts, but sometimes it is the result of a deliberate policy to prevent flooding in other more sensitive areas. In this way, historic buildings built on relatively high ground can be put at risk by measures taken to prevent further flooding of a larger number of new buildings built on flood plains or water meadows down stream.

Roof drainage, services and building failures
It is important to remember that many incidents of flooding in historic buildings are due to failures of roof drainage systems or other building services such as water mains. In these cases, water will often flood through buildings, causing damage to structures, furnishings and fittings, and accumulate in porous materials such as masonry, pugging or other insulation. These can then act as 'moisture reservoirs', providing the conditions for long-term damp and decay. This can be a particular problem in poorly maintained and infrequently occupied structures such as storerooms or the unoccupied parts of buildings in multiple occupation. The most catastrophic example of building failure causing flooding is fire. In this case, many thousands of litres of water may be used in fire fighting, and further water penetration occurs afterwards due to damage to roof drains and services. As a result, around four times as much damage is often caused by subsequent 'flooding' than is caused by the fire itself.

Careful enquiry and site investigation should identify some of the risk factors discussed above. Although some of these can be reduced, for example by repairing or re-detailing drainage, many are out of the direct control of building owners. It can be especially difficult to get municipal authorities to change street drainage and considerable lobbying and political pressure is required to get the responsible authorities to change the way they manage and maintain river catchments. In these circumstances, it is important to check that the building is not 'under insured' and that all the requirements of any insurance policy are fully met. In all cases, it is the responsibility of building owners to adequately maintain their property. They should also take all reasonable measures to mitigate their losses and reduce their risks. There are a number of refurbishment measures that can be taken to do this .

REFURBISHING FLOODED OR AT-RISK BUILDINGS

The first step in refurbishing flooded or at risk buildings is to reinstate the drainage systems so as to remove water from the structure and foundations. A checklist for this should include ground drainage, surface drainage, soakaways and sumps, if necessary. The latter may be installed without a permanent pump, but should be detailed to allow access in case of emergency.

The second step is to identify current or potential 'moisture reservoirs' in the structure so that appropriate measures can be taken to allow long-term drying and prevent damp or decay to vulnerable materials. This is a specialist task, but accumulations of pugging materials, debris or insulation under floors and the build-up of earth against walls are common problems in historic buildings. Almost by definition, most historic structures are inherently durable and are relatively resistant to flooding. It is therefore often cost-effective to remove any non-original materials, fixtures or finishes not required after refurbishment. These can be replaced with a material and detailing chosen to be resistant to water damage and to allow drying. Again, this is an area where specialist advice can be very useful. However, the general principals are to detail drainage, through-ventilate cavities, and to use breathable finishes. Fortunately, our ancestors were well aware of these requirements and excellent results can often be achieved by using original materials or techniques such as lime plasters and hardwoods or original details such as chimneys and cellars. Modern systems, including through-ventilated dry linings and highly breathable masonry paints, are also useful. Finishes vulnerable to damp or fluctuating moisture contents such as wood block flooring, MDF or veneers should be avoided .

Cob
Cob, clay lump and other forms of unbaked earth wall construction are particularly vulnerable to damage by water. To protect them from damp ground conditions, cob buildings are always built on top of a solid plinth of 300 to 600mm height. Depending on the part of the country, this plinth would be built from the local stone, flint or brick, which for added protection would often be tarred. If the floodwater rises above the plinth for any prolonged period, the cob will begin to disintegrate. To reduce the risk of flood damage, it is important to maintain the condition of the external plaster finish. Where the cob surface has eroded, it should be cleaned down and repaired with a low strength plaster such as 1:3:12 cement/ lime /sand or 1:25 moderately hydraulic lime/sand. Large holes should be filled with rubble stone rather than with new or reconstituted cob, as this would shrink and would therefore not adhere to the old work .

Drain water clear of the structure and, if required, prevent further water penetration by the use of temporary roof and ground drainage systems.

Remove* all damp materials and debris from the structure, including all damp furnishings, fittings, carpets, rubbish, damp infill and collapsed building materials.

Demolish* or otherwise remove* all parts of the structure not to be retained on refurbishment. In particular, remove any damp plaster, masonry masses or floor infills.

Provide through-ventilation to all parts of the structure, including all structural cavities such as sub-floor voids, chimney stacks and wall cavities. Fix all doors, cupboards, hatches and windows in a partially open position.

Identify all moisture reservoirs in the structure by calling upon a specialist surveyor.

Wherever possible, remove* all impermeable finishes from moisture reservoirs. Strip* all water and salt damaged plaster and finishes to expose the structures behind .

Detail refurbishment of the buildingto include moisture sinks, such as through ventilated dry lining systems, permeable or microporous finishes and structural heating systems, so as to allow continued drying during and after refurbishment The advice of a specialist surveyor should be sought. .

If required, consider the installation of accelerated drying machinery. The use of high capacity desiccant dehumidifiers, tenting and fans is recommended, as specified by an independent specialist surveyor. Consider the use of heating and mechanical ventilation systems. Note that effective accelerated drying requires much management time .

*NB If the building is listed, listed building consent may be required for these works and the advice of specialist surveyors should be sought .

~~~

A number of organisations are able to advise people with properties in areas known to be at risk of flooding:

Floodline - if you live in England or Wales phone 0845 988 1188 or visit the Floodline website (www.environment-agency.gov.uk) for detailed flood warning information for your area and advice on emergency actions in the event of flooding. Floodline is operated by the Envirornment Agency which is responsible for issuing flood warnings and arranging flood defence in England and Wales. In Scotland, this responsibility lies with the local authorities.

Local authorities are responsible for flood response during and after flooding. Consult the local phone directory or Yellow Pages or dial Directory Enquiries for the correct phone number. Local authorities will also advise on emergency accommodation.

Check radio, television, and newspapers for flood warnings and Meteorological 0ffice weather forecasts

If the property is a listed building, the local English Heritage office should be able to advise on its repair and restoration.

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Tim Hutton and Christopher Marsh Today, many property owners are understandably concerned by the risk and consequences of flooding. This is due to rising awareness of the effects of global warming and to the widespread flooding problems in the winter of 2000-01.

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High deforestation rates in Malaysian states hit by flooding

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Forest loss in five Malaysian states affected by flooding in Dec 2015. Five states hard hit by flooding last month in Malaysia had high rates of forest loss in recent years, bolstering assertions that environmental degradation may have worsened the disaster. According to satellite data from researchers led by the University of Maryland's Matt Hansen [...]

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Chure degradation over the years has worsened floods in Tarai districts

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Human activities are to blame for massive flooding down the Chure hills, environmentalists say.

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Abstract

This study is carried out in order to examine the impacts of flood events on water quality status of Muar River. The water samples consisting of six water quality parameters, namely dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, ammoniacal-nitrogen, pH value, and total suspended solids were used to compute the water quality index (WQI) at Muar River. Mean annually and monthly water quality variations of the nine sampling stations along Muar River over 2 years period (2006-2007) were investigated together with the monthly and annual rainfall pattern of the 22 rainfall stations within the basin. The relationship between monthly rainfall and water quality of Muar River for the period before and after the flood events was analyzed using Pearson correlation coefficient. In December 2006 and January 2007, the total monthly rainfall recorded was over 145 and 70 %, respectively, of the total monthly average rainfall of 31 years (from 1980 to 2010). The 2006/2007 Malaysian big flood events in December 2006 and January 2007 have resulted in lowest monthly WQI of 56.4 in Polluted category and within Class III in January 2007; while December 2006 and February 2007 flood events were categorized as Slightly Polluted and placed in Class III. Rainfall had higher correlation strengths with WQI and water quality parameters in the period before and during the first wave of flood events. Results of this study could be useful in supporting management decisions in mitigating the adverse effects of flood on the surface water resources.

Introduction

Flooding results from excessive rain on the land, or when a river or stream overflows its natural or artificial banks, flooding the surrounding floodplain. There are many different types of flooding but the most common are river floods, flash floods, coastal floods, and urban floods. Floods are recurring phenomena that can happen either slowly, through long periods of rainfall, or else, very quickly through sudden events like rainstorms. Although floods are natural phenomena, human activities could intervene with the natural process, e.g., alterations in the drainage patterns due to urbanization, agricultural practices, and deforestation, thus, considerably altering the river basins and resulting in larger sediment yields from water catchments (UNESCO 2011). Climate change processes could intensify the hydrological cycle, leading to abnormal frequencies in the occurrence and intensity of climatologic events. This could be manifested by more intense and temporally variable precipitation, greater occurrence and intensity of floods and droughts, more severe tropical storms, and increased wildfires (Sehmi 2009).

Major floods could incur great economic losses, particularly in densely populated urban areas and in more developed countries. Floods are in fact, the most damaging phenomena of all natural risks, affecting the socio-economic aspects of the population worldwide. The negative impacts of flooding include spread of communicable diseases; destruction of natural habitats, crops, livestock, homes, and properties; degradation in the water quality; and loss of natural vegetation and animals. Flooding puts life and property at risk as well as causing surface water pollution by overloading both the natural rivers and the artificial drainage.

Climate and rainfall are closely interrelated. Increasing rainfall variability and extremes as a consequence of climate change can influence surface water quality because the rainwater picks up surface materials, soils, wastes and other pollutants in runoff from slopes, open grounds, lawns, farms, streets, factories, and other areas into the receiving water bodies. Contamination of large water bodies is often much higher during and immediately after rainstorms (Water Research Foundation 2008), the increase in precipitation intensity is expected to lead to a deterioration of water quality, as it results in the inputs of pollutants particularly excessive nutrients, organic material, hazardous substances, pathogens, and other dissolved pollutants (e.g., pesticides); and in increased erosion, which in turn leads to the mobilization of adsorbed pollutants such as phosphorus and heavy metals into the surface waters and groundwater. Water pollution is a serious global problem that impacts the health of freshwater system, food production, and health care (Credit Valley Conservation 2009).

Malaysia, being located near the equator, receives full daily sunshine, with high relative humidity (ranging from 56 to 97 %), and high temperature (average of 27 °C or 80.6 °F) almost all the year round. The rainfall distribution in Malaysia is largely determined by intense convective precipitation with the coastal areas facing the South China Sea, and is highly influenced by the Northeast Monsoons (November-March) and Southwest Monsoons (May-September). The average annual rainfall is 2400 mm for Peninsular Malaysia, 3800 mm for Sarawak, and 2600 mm for Sabah. Malaysia experienced annual northeast monsoonal floods that vary in terms of severity and location. The northeast monsoon also brings heavy rainfall, which could persist for days on end. There are two transitional periods in between the two monsoons known as the inter-monsoon (April-May, October-November) when convectional thunderstorms are common (MMD 2010).

Trends in extreme precipitation events are receiving global attention due to global warming and climate change. In the periods of 17-20 December 2006, 24-28 December 2006, and 10-14 January 2007, Peninsular Malaysia was hit by a series of continual and abnormally heavy rainfall and storm events generated by the unusual Northeast Monsoon coming from the South China Sea and the West Pacific Ocean, and causing severe floods in the southern Peninsular states of Negeri Sembilan, Melaka, Pahang, and Johor. Abnormally high daily rainfalls of 200-300 mm were recorded in some of the rainfall stations in the Districts of Muar and Segamat, which had exceeded the long-term mean monthly rainfall for the region. The worst affected areas were along the major rivers such as the Johor River, the Batu Pahat River, the Segamat River, and the Muar River (DID Johor 2007). After the big flood events in December 2006 and January 2007, a smaller flood event had occurred in December 2007, with average total monthly rainfall of 368.84 mm.

Characteristics of the study area

The Muar River is the main artery of the Muar River Basin, flowing through the states of Negeri Sembilan, Pahang, and Johor in the south Peninsular Malaysia with the total length of 329 km. The origin of the river is a site called Jambu Lapan in Jempol, Negeri Sembilan, from which the upstream parts of the Muar River cover the central areas, Kuala Pilah of Negeri Sembilan, and the river then flows to the southeast region until Kampung Awat, then turns southwards at Bukit Kepong. The downstream part covers most of the Muar district in Johor, where the river flows southwest through the urban areas of Muar town, and finally entering the Malacca Straits at Kuala Muar, in Johor.

A river basin is the area of land from which all surface runoff flows through a sequence of streams, rivers and, possibly, lakes into the sea at a single river mouth, estuary or delta. The Muar River Basin, which lies from latitude 1 o52′00″ North to 2°54′00″ North and from longitude 102°14′00″ East to 103°04′00″ East, is a state transboundary river basin shared between the states of Negeri Sembilan, Johor, Melaka, and Pahang. The river basin covers an area of 6138 km ², of which, 3601 km ² (58.7 %) is located in Johor, while the rest (39.2 %) is in Negeri Sembilan, and small portions are located in Pahang (1.98 %) and in Melaka (0.13 %), respectively.

The major land use within the Muar River Basin is under natural forests, open grounds, swamps, scrub, and secondary growths, while the rest comprise oil palm and rubber plantations, agriculture, settlement areas, and other land uses. The densely populated areas are in the urban townships of Muar, Segamat, Labis, Gemas, and Kuala Pilah (DOA Malaysia 2006). The rapid rise in human population and urbanization in recent years have resulted in the gradual deterioration of the water quality of the Muar River, particularly due to discharges of industrial wastewater and agricultural runoff.

The Muar River is one of the large and important rivers in Malaysia, with significant influence over the socio-economic status of the surrounding communities. It is the main source of livelihood, water and protein supply (fishery resources), and the major mode of transportation for the community, for trade and commerce. In the modern times, the Muar River still has very much to offer to its communities, especially in terms of agriculture, aquaculture, and recreational activities (leisure fishing, boating, etc.), and it is still the sole source of drinking water for the entire Muar District, a large section of the Ledang District and a reserved water reservoir for the Melaka state.

Materials and methods

For the purpose of this study, a 2-year water quality data from January 2006 to November 2007 were acquired from the Department of Irrigation and Drainage (DID) Malaysia and Department of Environment (DOE) Malaysia for the nine water quality monitoring stations located along the Muar River. For each site, a total of six water quality variables, i.e., Dissolved oxygen (DO), Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), pH value (pH), ammoniacal-nitrogen (AN/NH ₃-N), and total suspended solids (TSS) were analyzed to derive the water quality index (WQI) of the Muar River.

WQI has been developed to assess the suitability of water for a variety of uses. Different pollutants and factors are required for the development of an index. Most of the WQI development in many countries requires selection of water quality parameters and assigning optional weights of the selected parameters. WQI combines a group of important water quality parameters that give an overall index of the water quality for a specific use (Davis and McCuen 2005).

The WQI approved by the DOE Malaysia is an opinion-poll formula, the determining processes were based on personal evaluation, namely, opinion-gathering and questionnaire survey techniques used to develop WQI where selected influential variables were identified with respective weights. The WQI was used as a basis for assessment of a watercourse in relation to pollution load categorization and comprises weighted linear aggregation of sub-indices of DO, BOD, COD, AN, SS, and pH. These parameters were selected by the panel of experts as being the parameters that will give some indication on the water quality level or WQI of a river (DOE Malaysia 1994) when calculated and used collectively. The concentration of each parameter in the water body may have different effects on human health and aquatic species, this concentration is a measurable value and the value of effects it carries is unitless that needs to be quantified. This unitless value is the sub-index value and is obtained from sub-index structure, which is the basic structure that relates to the effect of concentration for a specific parameter.

In order to obtain a sub-index value from each parameter, each panelist drew a curve which they felt best represented the variation in water quality produced by the various levels of each parameter; levels of water quality range from 0 to 100 were indicated on the y-axis of each graph while increasing levels of the particular parameter were indicated on the x-axis. Then, all the curves had been averaged to produce a single line for each parameter, so that the sub-index value for the concentration of each parameter can readily be obtained on a common scale from 0 to 100, higher value of the index indicates better quality of water. Each sub-index will be aggregated with other sub-indices to give a final WQI value. Thus, each rating curve needs to be transformed into mathematical equations to aggregate it appropriately. Statistical analysis of the ratings was used to assign weights to each parameter, where the sum of the weights is equal to 1. In water quality, weight denotes the relative importance of each water quality parameter and is used to consider differences in the importance of parameter. Weight is also defined as relative weight or importance weighting factor (Dunnette 1979), weighting factor (Inhaber 1975), and perceived importance (Smith 1990). The weights for each variable indicate the relative importance of the variables in determining WQI in Malaysia. Among them DO carries maximum weightage of 0.22 and pH carries the minimum of 0.12 in the WQI equation.

The WQI is a unitless number and calculated from the Eq. 1 as given below, the sub-index value multiplied with the weighing factor to get the weighted value of sub-index for calculating the WQI.

where SI refers to the sub-index function for each of the given parameters, SIDO = Sub-index of DO, SIBOD = Sub-index of BOD, SICOD = Sub-index of COD, SIAN = Sub-index of NH ₃-N, SISS = Sub-index of SS, SIpH = Sub-index of pH.

Sub-indexes values are calculated according to the best fit equations given in Eqs. 2-7. Sub-index for DO (in % saturation):

Sub-index for BOD:

Sub-index for COD:

Sub-index for AN/NH ₃-N:

Sub-index for SS:

Sub-index for pH:

The calculated WQI should fall within the range of 0 ≤ WQI ≤ 100, a higher index value represents better water quality. 100 is the highest possible score and denotes a pristine river and zero is the lowest. The WQI score can then be used to categorize a particular water body into one of five classes as provided for under the National Water Quality Standards for Malaysia (NWQS) (Table 1).

Table 1 Class based-DOE water quality index classification

The WQI for rating the water quality in terms of a number has been used to indicate the degree of water pollution status (Table 2) and designation of classes of beneficial uses (Table 3), which makes it easily understandable for communities in the river basin and for river basin management. The WQI is widely used to evaluate the overall water quality of the rivers and as a tool in water quality classification according to the NWQS. By computing the WQI, the DOE, DID, and other relevant authorities could determine the cleanliness and availability of river water for domestic water supply, aquatic life, livestock drinking, recreational, and agricultural use (DOE Malaysia 1985). The water quality is considered to be suitable for a specific use as long as it is within the range specified for the designated class.

Table 2 Pollution status based-DOE water quality classification based on water quality index

Table 3 Water Quality Classes and Uses (National Water Quality Standards for Malaysia)

The historic weather data from January 1980 to December 2010 of the 22 rainfall stations in the Muar River Basin area, covering 31 years, were obtained from the DID Malaysia and the Malaysian Meteorological Department (MMD). The rainfall data of the 31 years, which included the 2006/2007 big flood events were used to analyze the mean monthly and annual rainfall patterns from 1980 to 2010 in the Muar River Basin area. Figure 1 shows the base map of the Muar River Basin that has been prepared from the topographic maps of Kuala Pilah (JUPEM 1997), Bahau (JUPEM 1995), Gemencheh (JUPEM 1996), Segamat (JUPEM 1995), Gerisek (JUPEM 1997), Muar (JUPEM 2006), Bakri (JUPEM 2007) with the identified 22 rainfall stations in the area of Muar River Basin and the nine water quality stations along the Muar River.

In this study, the annual and monthly WQI of the Muar River in the period before, during, and after the 2006/07 big flood events was analyzed against the annual and monthly rainfall patterns of the Muar River Basin from January 2006 to December 2007. To investigate the effects of high rainfall and floods on the water quality of the Muar River, Pearson correlation coefficient ( r) test was performed. Correlation coefficient between the rainfall volume with the sub-index for each of the water quality parameters in WQI formula and the WQI value; and the correlation among the sub-index for all of the six water quality parameters and the WQI value were calculated for the period before the flood events (from January 2006 until the month of first wave flood events, December 2006) and the period after the flood events (from the month of second wave flood events, January 2007 and the months after the flood events until November 2007) to determine if the relationships differed between before and after the 2006/07 big flood events. Statistical significance was tested at the alpha level of 0.05, 0.02, and 0.01 with 95, 98, and 99 % confidence level, respectively.

Results and discussion

Rainfall pattern

The characteristic features of the rainfall pattern in the Muar River Basin were analyzed based on a 31-year period data (1980-2010) recorded at the 22 rainfall stations. The mean monthly rainfall and mean monthly rain days (≥0.1 mm of rainfall per day) of the 22 rainfall stations in the area for the year 1980-2010 are shown in Fig. 2. The analyzed results showed that the Muar River Basin had an average annual rainfall of 1707 ± 250 mm, and the average monthly rainfall of 146 ± 31 mm. The mean annual rain days and the mean monthly rain days in the area were 118.4 ± 12.4 and 9.34 ± 1.72 days, respectively. From 1980 to 2010, the maximum rainfall was recorded in November and December, during the Northeast Monsoon. The highest average total monthly rainfall of 198.1 mm was recorded in November, and followed by 187.5 mm in December. November was the month with the highest average monthly heavy rain days (50 < X < 100 mm/day) of 14 h, the highest average monthly moderate rain days (10 < X ≤ 50 mm/day) of five days, and the highest average monthly light rain days (≤10 mm/day) of 6 days 15 h, while December was the month with the highest average monthly with very heavy rain days (≥100 mm/day) of 5 h. The lowest mean monthly rainfall of 90.1 mm was in February, and the second lowest mean monthly rainfall of 107.3 mm was in June.

Rainfall and water quality index (WQI)

Figure 3 gives the monthly rainfall pattern of the 22 rainfall stations in the Muar River Basin for 2006 and 2007, and the change in the WQI from January 2006 to November 2007 for nine sampling stations of the Muar River. The average total annual rainfall in 2006 was 2090.8 mm and for 2007, was 2150.5 mm, which ranged as the second and third highest annual rainfall for the period from 1980 to 2010. According to the NWQS, the WQI values of the Muar River for year 2006 and 2007 were classified under Class II, where a higher WQI value of 83.2 was recorded in 2006, with the index range of clean, while a WQI value of 78.1 was recorded in 2007, with the index range of Slightly Polluted (Table 4).

Table 4 Water quality Class-based classification according to the concentration of NH₃-N, BOD, COD, DO, pH, TSS, and the WQI; and Water quality pollution Status-based classification according to the SIAN, SIBOD, SISS, and WQI of the Muar River from January 2006 to November 2007

During the Northeast Monsoon from January to March 2006, the WQI for January 2006 was 79.06, with high rainfall record of 46 % above the monthly average rainfall for the period of 1980-2010. The lower total monthly rainfall of 118.3 and 100.2 mm recorded for February and March 2006, corresponded with the higher WQI of 81.7 and 84.9, respectively (Fig. 3). These results indicated that the water quality status of the Muar River had lower WQI for those months with higher total monthly rainfall. During the inter-monsoon in April 2006, the total monthly rainfall had higher volume of 134.8 mm compared to February and March 2006, the WQI for the Muar River had degraded to 74.4 (Fig. 3), within Class III (Table 4). These results indicated that the higher rainfall after 2 months of relatively lower rainfall had worsened the water quality due to accumulated pollutant loads from the surrounding non-point sources, particularly the urban areas.

During the Southwest Monsoon from May to September 2006, the WQI of the Muar River was in Class II. Compared to April 2006, May 2006 had higher rainfall of 183.4 mm and WQI value of 81.5. From June until September, the monthly WQI value of the Muar River was lower when the total monthly rainfall was lower; whereby the lowest rainfall of 90.1 mm occurred in August, with the lowest WQI of 80.78, while the second lowest rainfall of 94.3 mm was in September, with a higher WQI of 83.5. In July, a higher rainfall of 116.5 mm corresponded with the higher WQI of 87.9, while the highest rainfall of 144.1 mm (in June) was correlated the highest WQI of 90.3. The total monthly rainfall had increased 49.3 mm in the inter-monsoon month of October 2006 compared to September 2006. The WQI of the Muar River was 93.6 in October, i.e., the only month in year 2006 when the river was categorized as Clean, with WQI classified under Class I (Fig. 3; Table 4). The WQI data for the Southwest Monsoon and the inter-monsoon month of October showed comparatively lower pollutant loads, probably due to the dilution effect of increased water volume in the Muar River.

During the Northeast Monsoon, the total monthly rainfall in November 2006 had increased 34 % compared to October 2006, the WQI dropped to 84.5, within Class II. The total monthly rainfall in December 2006 was over 145 % of the total monthly average of 187.5 mm, while January 2007 received total monthly rainfall more than 70 % of the total monthly average rainfall of 138.2 mm. The Muar River was classified as Class III in December 2006 and January 2007, and December 2006 was the month when the first wave of 2006/07 flood events had occurred, with the WQI of 75.79 and in Slightly Polluted category. However, in January 2007 the WQI had dropped drastically to 56.4 and in Polluted category (Fig. 3; Table 4), which corresponded with the second wave of 2006/07 flood events. Based on the WQI, the water quality class of Muar River for the months of December 2006 and January 2007 required extensive treatment for water supply purposes, being suitable only for very tolerant and most common aquatic species such as the gastropod molluscs, polychaete worms, and hardy fish such as tilapia, and maybe for livestock drinking.

After the big flood events, the lowest mean monthly rainfall of 62.08 mm in a 2-year period (2006-2007) was recorded in February 2007, i.e., 28 mm below the monthly average rainfall of the 31-year record. The WQI value of February 2007 was categorized as Slightly Polluted and within Class III. However, about 1 month after the big flood events (in March), the WQI of the Muar River had recovered back to normal, with index range of Clean and classified under Class II. This could be due to the good water circulation, dilution, and mixing, where in March 2007 it had received more than 133 percent of the February 2007 rainfall volume. According to the DOE, the WQI and river water quality of Class II is suitable for potable water supply but conventional treatment is required, the water quality status is suitable for sensitive aquatic species and for recreational use involving body contact.

Form March until June 2007, WQI of the Muar River was classified under Class II with index range of Clean, and the received rainfall ranged from 130.1 mm in June to 147.4 mm in April. The WQI of the Muar River was degraded into Class III and categorized as Slightly Polluted in July 2007, with higher rainfall of 180.5 mm, 49 % above the monthly average rainfall. The WQI of the Muar River was classified under Class II from August to November 2007, with lower rainfall recorded in September (108.4 mm) and November 2007 (139.1 mm), and these 2 months have WQI range of Clean; but with higher rainfall found in the months of August (141.39 mm) and October 2007 (205.8 mm), respectively, the WQI for August and October 2007 were classified as Slightly Polluted. The highest average total monthly rainfall in 2007 was recorded in December with 97 % well above the monthly average rainfall of the years from 1980 to 2010. The high rainfall volume had triggering another prolonged flood event in the Muar River Basin from the 2nd to 17th December 2007.

Correlation analysis

In the period before the flood events and during the first wave of flood events from January 2006 to December 2006, Pearson's r correlation analysis between monthly rainfall and water quality parameters showed that there are highly significant negative relationship between rainfall and DO ( r = −0.784, P < 0.01), that means if the rainfall volume increases, the DO concentration obtained is lower and vice versa. Thus, high precipitations would lead to deterioration of water quality. However, the results showed that no statistical significance in monthly rainfall with the WQI value and the parameters of NH ₃-N, BOD, COD, pH, and SS. There are three significant relationships among water quality parameters calculated, SS had a significant positive relationship with NH ₃-N ( r = 0.599, P < 0.05), and a highly significant negative relationship with pH ( r = −0.796, P < 0.01), and pH had a significant positive relationship with DO ( r = 0.617, P < 0.05); while BOD and COD was found did not have significant relationships with the other water quality parameters. There are significant correlations between WQI and water quality parameters of NH ₃-N, COD, pH, and SS. The WQI value was positively correlated with pH ( r = 0.722, P < 0.01), and negatively correlated with NH ₃-N ( r = −0.669, P < 0.02), COD ( r = −0.714, P < 0.01), and SS ( r = −0.912, P < 0.01) (Table 5).

Table 5 Pearson correlation coefficient (r) for the rainfall in Muar River Basin, the water quality parameters in the Muar River, and the calculated WQI in the period from January 2006 to December 2006

During the period of second wave flood events and after the flood events from January 2007 to November 2007, there are no significant correlations between the amounts of rainfall with the WQI value and the water quality parameters. There are eight significant relationships among the six physicochemical water quality parameters, the concentration of NH ₃-N was the only variable significantly correlated with all the other five water quality parameters, NH ₃-N had a significant positive relationship with BOD ( r = 0.688, P < 0.02), COD ( r = 0.870, P < 0.01), and SS ( r = 0.692, P < 0.02), and a significant negative relationship with DO ( r = −0.670, P < 0.05) and pH ( r = −0.778, P < 0.01). A highly significant positive relationship existed between SS and COD ( r = 0.791, P < 0.01), and a significant negative correlation was found between COD and DO ( r = −0.607, P < 0.05), while DO and pH ( r = 0.722, P < 0.01) revealed a highly significant positive relationship. Except BOD, water quality parameters of NH ₃-N, COD, DO, pH, and SS had a highly significant very strong relationship with WQI. Correlation analysis showed that WQI had a positive relationship with DO ( r = 0.753, P < 0.01) and pH ( r = 0.837, P < 0.01), and a negative relationship with NH ₃-N ( r = −0.908, P < 0.01), COD ( r = −0.839, P < 0.01), and SS ( r = −0.836, P < 0.01) (Table 6).

Table 6 Pearson correlation coefficient (r) for the rainfall in Muar River Basin, the water quality parameters in the Muar River, and the calculated WQI in the period from January 2007 to November 2007

For overall correlation analysis for the period from January 2006 to November 2007, rainfall had a positive relationship with NH ₃-N, BOD, and SS, and had a negative relationship with COD, DO, pH, and WQI. Lower strengths of correlations were found between rainfall with the water quality parameters and WQI in the period of second wave flood events and after the flood events in the year 2007 compared to the period before the flood events and during the first wave of flood events in the year 2006. The strength of correlation between rainfall with NH ₃-N and SS was decreased from strong relationship in year 2006 to no or negligible relationship in year 2007; rainfall and DO correlation strength was decreased from very strong relationship in year 2006 to moderate relationship in year 2007; rainfall and pH had a strong relationship in year 2006 and 2007, but the strength of correlation have decreased from high correlation ( r = −0.527) in year 2006 to medium correlation ( r = −0.494) in year 2007; and there had no or negligible relationship between the amount of rainfall with BOD and COD in year 2006 and 2007; while the correlation between rainfall and WQI had the strength of strong relationship in year 2006 and moderate relationship in year 2007. Except the strength of correlation between WQI and SS found higher in year 2006, the correlations between WQI and the other 5 water quality parameters had higher strengths in year 2007. The strengths of correlations among the water quality parameters were found lower in year 2006, except for the correlation between pH and SS which was of lower strength of correlation in the year 2007.

Rainfall and water quality parameters

The water quality results clearly showed that in terms of DO, BOD, COD, pH, NH ₃-N, and TSS, the Muar River water had degraded during the study period, most likely due to the long-term flooding.

Dissolved oxygen (DO)

DO is a measure of the quantity of oxygen gas freely available in water, the level of DO in river is important from an environmental perspective. DO is vital to all forms of aquatic life such as plants, fish, microorganisms, invertebrates, and others. Concentrations of unpolluted fresh water will be close to 10 mg/l. Numerous scientific studies suggest that 4-5 mg/l of DO is the minimum amount that will support a large, diverse fish population. Typically DO levels less than 2 mg/l will kill fish.

The DO levels were classified under Class II within the study period from January 2006 to November 2007, the DO concentration ranged from 5.03 mg/l (January 2007) to 6.54 mg/l (September 2006) as can be clearly seen in Fig. 4. The DO mean level in the Muar River prior to the big flood events was 5.46 mg/l in November 2006, but had only dropped slightly to 5.24 and 5.03 mg/l in December 2006 and January 2007, respectively. The DO levels were lower during the flood events, possibly due to the high pollutant loads such as organics and nutrients that were discharged into the Muar River together with the floodwater, the breakdown of organic material can depress oxygen levels for days or even weeks.

Biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD)

Other indirect laboratory tests for assessing the DO are the BOD and COD. Bacteria in the water degrade the organic pollution, utilizing DO in the process. The amount of oxygen required to decompose organic matter in a unit volume of water is called the BOD. COD does not differentiate between biologically available and inert organic matter, and it is a measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. The main difference between BOD and COD test is that while BOD determines compounds that can be biologically oxidized, COD measures those substances which can be chemically oxidized. COD values are always greater than BOD values, COD test can be made in a few hours while BOD test is performed over a 5 day period, so it is referred to as a "five day BOD (BOD ₅)."

The monthly BOD ₅ and COD concentrations in the Muar River for the period from January 2006 to November 2007 are presented in Figs. 5 and 6. The BOD ₅ of the Muar River water was categorized as Clean and under Class II from January 2006 to November 2007, except during the flood events in January 2007, and the month after the flood events, in February 2007, the BOD ₅ was categorized as Slightly Polluted and under Class II; while the COD was under Class II in November and December 2006 and had then degraded into Class III in January and February 2007 (Table 4).

Urban runoff during the flood events had increased loads of domestic wastes from the streets and sidewalks; nutrients from untreated sewage, discharges from agro-based industries, and manufacturing industries; leaves, grass clippings, and stormwater inputs from residential areas, all of which had increased the oxygen demand in the river. The oxygen utilized for elevated decomposition process of various organic wastes had deprived the aquatic organisms of their vital oxygen supply.

pH

In natural waters, the pH scale runs from 0 to 14. The pH of water should be at 7 which is neutral, pH values less than 7 indicate acidic water having corrosive properties, and pH values greater than 7 indicate alkaline properties. Most aquatic lives are sensitive to pH variations, leading to fish kills and reduction and changes in aquatic communities when the pH is altered outside their tolerance limits of pH 5-9.

The pH values which measure the acidity or alkalinity of the water were the most affected parameter during the flood events, as seen in Fig. 7, where the pH value recorded was 6.2 and was within Class II in November and December 2006, but had dropped to 3.2 and classified as Class IV during the second wave of flood events in January 2007 (Table 4). The river water during the second wave flooding recorded pH 3.2, which had exceeded the NWQS and not suitable for water supply purposes.

However, after the big flood events, in February 2007, the pH had increased to normal level of 5.8 and within Class II. Most of the pH impacts during the flood events were likely caused by excessive runoff with chemicals and pollutants from agriculture practices and irrigating lands, anthropogenic and industrial pollutants, organic wastes, and sewage from the basin area; the heavy rainfall and acid precipitation have caused the leaching of acid and metals concurrently into the water, which can have an immediate or a long-term effect by influencing the chemical composition and pH fluctuations of the water. The pH of water affects the solubility of metals and nutritive chemicals, most metals become more water soluble and more toxic when pH of river decreases, while ammonia becomes more toxic in river with a slight increase in pH.

Ammoniacal-nitrogen (NH₃-N)

Before the 2006/2007 flood events, the NH ₃-N levels in the Muar River was classified under Class I with WQI range of Clean in October and November 2006. However, it became classified as Slightly Polluted and within Class II in December 2006 during the first wave of flood events, and had degraded into Class III with WQI range of Polluted and Slightly Polluted in January and February 2007, respectively (Fig. 8; Table 4). Higher concentrations of NH ₃-N found in the Muar River during and after the big flood events could be an indication of heavily loaded with eroded soil and nitrogenous inputs from livestock farming, domestic sewage, industrial waste, and fertilizer runoff. The NH ₃-N form detected in the water is the nitrogen form that is most readily toxic to aquatic life above the tolerable limits. NH ₃-N is formed by chemical and bacterial decomposition of breakdown of the principally protein-bearing materials.

Monthly ammoniacal-nitrogen (NH ₃-N) concentrations in the Muar River for the year 2006 and 2007

Total suspended solids (TSS)

TSS is defined as the solid matter in a water sample that can be retained on a glass fiber filter with a pore size less than 2 µm, typically consisting of fragmental minerals, silt, plankton, sand, nutrients, and metals that have attached to the particles in the water. Figure 9 brings out the concentrations of TSS in the Muar River from January 2006 to November 2007. In November 2006, the TSS was 44 mg/l, classified in Class II with WQI range of Slightly Polluted. The TSS was degraded to Class III with WQI range of Polluted in the months of December 2006, January, and February 2007. TSS recorded was 84.2 and 130 mg/l in the flooding months of December 2006 and January 2007, respectively. After the big flood events, in February 2007, TSS had increased to 144.6 mg/l. The TSS increase was likely due to the high rainfall and flooding, since particles eroded from the soil surface by the rainfall would be carried in the runoff and deposited as bottom sediments in the river, later to be churned up and re-suspended by further rainfall events.

TSS are materials suspended in the water and high levels of suspended solids in water are capable to settle out onto the streambed, sediment can cover aquatic organisms, eggs, or macro-invertebrate larva in the water bed. This coating can prevent sufficient oxygen transfer and result in the death of buried organisms. High concentrations of suspended solids can lower water quality by increasing the water temperature and water density, reducing the solubility of oxygen gas and water clarity, and affecting osmoregulation of fresh water organisms.

Conclusion

In this study, the effects of the big flood events of 2006/2007 and the high amounts of rainfall on the river water quality of the Muar River were analyzed based on documented data. The flood events and the amount of rainfall are the key factors affecting the river water quality. Based on the results analysis from this study, DO concentration in Muar River has a general pattern where it is lower during high rainfall period from October to December. The relationship among water quality parameters indicate that high concentration of SS in Muar River caused an increase in the concentration of NH ₃-N and decreased in pH, and the decrease of pH value had caused lower DO concentration in Muar River. The results of analysis indicate that heavy rainfall and surface runoff had increased the pollutant loads into the Muar River, thus impacting its water quality. The rainfall variability and the flood events that had occurred in the Muar River Basin represented a major challenge in utilizing the Muar River for potable water supply in the area. Watershed characteristics are dependent on the type of surrounding land cover, thus, prescribed activities involving land-use change should be carefully planned and managed since the treatment of polluted water involves substantial cost to the water provider and to the public. It is crucial to ensure that new developments are not approved in flood-prone areas nor allowed to increase the risk of flooding elsewhere.

Acknowledgments

We would like to express our sincere thanks and appreciation to the Department of Irrigation and Drainage Malaysia and Johor State, the Malaysian Meteorological Department, the Department of Environment Malaysia, the Department of Survey and Mapping Malaysia, the Department of Agriculture Malaysia, respectively, for their support and permission to use the data and information for this study and its publication. This study has been funded by the Malaysian Research University Grants UKM-GUP-PLW-08-12-050.

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Affiliations

1. Faculty of Science and Technology, National University of Malaysia, UKM, 43600, Bangi, Selangor, Malaysia

Yun Chen Ching, Yook Heng Lee, Maimon Abdullah & Baharudin Bin Yatim

2. Faculty of Social Sciences and Humanities, National University of Malaysia, UKM, 43600, Bangi, Selangor, Malaysia

Mohd Ekhwan Toriman

3. East Coast Environmental Research Institute, Universiti Sultan Zainal Abidin, (UniSZA), Kuala Terengganu, Terengganu, Malaysia

Mohd Ekhwan Toriman

Corresponding author

Correspondence to Yun Chen Ching.

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Ching, Y.C., Lee, Y.H., Toriman, M.E. et al. Effect of the big flood events on the water quality of the Muar River, Malaysia. Sustain. Water Resour. Manag. 1, 97-110 (2015). https://doi.org/10.1007/s40899-015-0009-4
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Keywords

Flood events

Muar River

Water quality parameters

Water quality index (WQI)

Rainfall

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Effect of the big flood events on the water quality of the Muar River, Malaysia - Sustainable Water Resources Management

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This study is carried out in order to examine the impacts of flood events on water quality status of Muar River. The water samples consisting of six water quality parameters, namely dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, ammoniacal-nitrogen, pH value, and total suspended solids were used to compute the water quality index (WQI) at Muar River.