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Decades ago, floods occur far and between but recent increase in flooding in the most unexpected places across the world is a cause for alarm. It is obvious now that flooding disasters are no longer confined in the remote regions. Previously, flooding is expected only in areas beside rivers, coasts and low-lying areas. Recently, even modern cities like New York, Queesland, Bangkok, and many others have not been spared from being submerged under flood waters.
A flood may be caused by a weather disturbance such as typhoon or a hurricane, storm surges, ice melt, heavy rain. Still, floods can also be caused by dams or levees breaking, snow and snow melt.
The wide devastation brought by flash floods had not only claimed lives and properties but it had impact on how governments have prepared for their onslaught. There is no assurance that a location is flood-free. It seems that flooding disasters has become the new normal. It is an important issue that all concerned sectors have to tackle and be prepared with.
In the United States alone, floods kills more people each year than tornadoes, hurricane or lighting according to the National Severe Storms Laboratory.
Most recently, New York, Queensland, Bangkok, Manila and Beijing have seen the devastation wrought by these floods. Global warming and climate change are often pointed as the culprit. Admittedly, both nature and man have so far contribute to the occurrence of such disaster. The only difference is that the magnitude of recent floods is far beyond what people have prepared themselves for.
Manila was a Waterworld in 2009
The city of Manila in the Philippines was not spared from flash floods brought by heavy torrential rains of super typhoon Ondoy (Ketsana) that claimed more than 464 lives in September 2009. While typhoon Wishi claimed over 1,000 lives in the southern cities of Cagayan de Oro and Iligan in Mindanao in December 2010.
A flash flood occurs within a very shot interval period of 2-6 hours from the occurence of heavy rain, storm or typhoon, dam break or levee failure, and even ice melt or jam. It can also occur slowly when there is minimal but non-stop rain over a period of days or weeks in one area. Other factors contributing to the occurrence of flash floods are topography, soil, and surface cover.
Flash floods often occur when heavy rain pours within a short period of time from upstream causing water rapidly descends through rivers and streams and inundating low-lying areas downstream. It can also be worsened by the increasing construction of cities and concreting of wide areas contributing to the lack of surface absorbing the rains. Areas soil having clay-like properties are also prone to flash floods and mud slides. In some instances, environmental degradation like illegal logging could exacerbated the damage of flash floods. The lack of surface cover such as trees to help absorb water cause the water to cascade rapidly down to lower areas. This was one of the causes being looked into in the case of the recent Philippine flash floods.
A chilling video on flash flood within a village
Causes of Floods
Heavy Rain. Continuous rain within a short time period often causes the rapid rise of water filling rivers. The overflow of these rivers into communities is caused many flash floods with half an hour from the start of a heavy rain.
Storm Surges. High winds brought by tropical storms can cause seas to swell and overflow into coastal areas.
Dam Break or Levee Failure. Dam breaks don't occur too often since many of these dams have now been built with strong concrete. However, the possibility of one occurring is still high with record rains associated with typhoons causing overflow and strong water current. Levee failures are often associated with severe downpour causing the overflows of rivers. When levees are not strong enough, pressure builds in its walls causing it to break.
Snow Melt. A snow melt can cause flash floods when water coming from melting snow in mountains rapidly descend to low-lying areas. The waters may bring mud and other debris along its path.
Ice Jams. Flash floods will also occur when frozen rivers thaw causing the broken ice to clog drainage flows and thus, trap water in some areas which results to a rise in water levels and overflowing into residential communities.
Recent Flash Floods
2010 - Queensland. A flash flood raced through the Toowoomba Central business district in 2010. Total death count is 35 with 9 people missing.
2011 - Victoria. The state of Victoria had the 'worst flood in its history' caused by massive rainfall. Floodwaters caused damage to considerable properties and livestock . It was so widespread that Victoria transformed into an inland sea affecting many communities, destroying homes and displacing thousands of residents.
2011 - Beijing. Massive floods struck hurtling across the busy central business district during rush hour to the surprise of unsuspecting city-dwellers.
2010 - Arkansas. Dozens went missing when icy waters swept race through the Arkansas valley tearing cabins and tents into pieces. The flash floods were caused by the heavy torrential rains the night before which caused some rivers to swell and overflow. Survivors compare the flash floods to a 'tsunami'.The flood claimed the lives of 18 people and dozens more missing.
2012 - New York. Flood waters crippled the city for days when rains and storm surge caused by hurricane Sandy flooded lower Manhattan submerging subways and knocking power.
2009 - Metro Manila. Super typhoon Ondoy (Ketsana) caused massive flash floods across Metro Manila submerging countless cities for days, while for some, even months. The record rainfall dumped a month's worth of rain in barely 12 hours in this densely populated metropolitan area causing million in damage to property and loss of lives totaling 464. Nobody thought such magnitude of flooding would happen in this city, but it did.
2011 - Cagayan de Oro, Iligan, Negros. The cities of Cagayan de Oro and Iligan were the worst hit when flash floods inundated coastal villages and those beside rivers when most people were sleeping on the wee hours of Dec 17, 2011. The flash floods were due to the high rainfall brought by the Typhone Sendong (Washi). Communities and villages were totally wiped out within hours as racing waters carrying mud, logs and debris carved its way across the city. The aftermath showed the chilling devastation and loss of life in what were previously considered as 'typhoon-free' cities in this part of the country. Survivors recount the nightmare and how water rose within minutes and how they managed to flee with no time to spare, bringing nothing with them except the clothes they have on.
December 2012. Typhoon Pablo cause massive landslides and mud which claimed more than 600 lives with probably a thousand more missing in the towns of New Bataan and neighboring areas in Compostella Valley, in Southern Philippines.
The prevalence of the flash floods everywhere can never be ignored. It appears that nature is telling us something, we fail to see in the past or ignore. Something is going on our environment that these days, no one and no country can claim to be safe from the havoc brought by a flash floods. There is no more specific areas that one can say is safe from flash floods, but people who live in low-lying, coastal areas, beside rivers and streams, well almost everywhere, must be extra vigilant when weather disturbances such as storms or typhoons are predicted.
A timely warning, quick thinking and immediate action by the residents of high-prone areas could help, but that's the least that people can do. These days, during storms or typhoons, everyone, wherever you are, the best motto should be to 'Brace for the worst' because whether you like it or not, flash floods will continue to wreak its havoc and no one is safe.