Flash Floods


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Flash Floods

  1. 1. Flash Floods BY YEAR 12
  2. 2. WHAT ARE FLASH FLOODS? By Corley and Claire. -A sudden flood of great volume , usually caused by a heavy rain,  or failure of dam or the thaw of an ice jam .  . These fast moving waters can move boulders , tear out trees , and destroy buildings . -Occurs suddenly in a short duration   -Little or no advance warning,over a relatively small area Picture:  A flash flood after a thunderstorm in the Gobi, Mongolia.
  3. 3. Causes of Flash Floods <ul><ul><li>When a barrier holding the water such as a dam fails. </li></ul></ul><ul><ul><li>When the ground can either be too hard or too wet to soak up any water, so the water flows downstream. </li></ul></ul><ul><ul><li>Rainfall of more than one inch/hour is needed to start a flash flood. </li></ul></ul><ul><ul><li>Even if the area that's hit by a flash flood is sunny, there is still the possibility of a flash flood if it is raining heavily somewhere uphill even dozens of miles from the source. </li></ul></ul><ul><ul><li>Very heavy rain. </li></ul></ul>By Charlotte Lee Andersen & Katlyn Yip
  4. 4. WHAT ARE THE EFFECTS? <ul><ul><li>Many people are caught unprepared for the power and speed of a flash flood, which results in dangerous situations.The effects can lead to many deaths or the destruction of vegetation. </li></ul></ul><ul><ul><li>Floods destroy drainage systems in cities, causing raw sewage to spill out into water. In cases of severe floods, buildings can be significantly damaged and even destroyed.  </li></ul></ul><ul><ul><li>This can lead to catastrophic effects on the environment as many toxic materials such as paint, pesticide and gasoline can be released into the rivers, lakes, bays, and ocean, killing marine-life.  </li></ul></ul><ul><ul><li>Floods may also cause millions of dollars worth of damage to a city, both evicting people from their homes and ruining businesses. An example is in Jiangxi of China 1998.  </li></ul></ul><ul><ul><li>  Floods cause significant amounts of erosion to coasts, leading to more frequent flooding if not repaired. </li></ul></ul><ul><ul><li>Because flash floods pick up lots of sediment the water turns muddy and could affect the transportation methods such as roads. It may also affect oasis's if the water enters the oasis. </li></ul></ul>
  5. 5. Frequency (Mike and Raoul) <ul><ul><li>Occur after heavy rain (sand cannot soak up a lot of water) </li></ul></ul><ul><ul><li>From 1996-2003, an average of 3000 flash floods occured in the USA alone each year  </li></ul></ul><ul><ul><li>  Occur more frequently in areas of steep terrain, excessive antecedent preciptiation and thin, bare of impermeable </li></ul></ul><ul><ul><li>Example: Texas (flash-flood valley) </li></ul></ul><ul><ul><li>Flash flood reports in the U.S. are on the increase partly due to increased emphasis by the National Weather Service to report floods </li></ul></ul>
  6. 6. Case Study of Flash Flood (1) <ul><li>Causes of the Flash Flood in Kentuckiana : </li></ul><ul><ul><li>August 4th,9:25am - A cold front moved across the American Mid-west from a major thunderstorm from the North-West </li></ul></ul><ul><ul><li>The cold front caused :  </li></ul></ul><ul><ul><ul><li>large hails </li></ul></ul></ul><ul><ul><ul><li>winds exceeding 97km/h   </li></ul></ul></ul><ul><ul><ul><li>rainfall of 14-24cm in less than 1 hours (according to National Weather Service) </li></ul></ul></ul><ul><ul><ul><li>More rain fell than the normal the entire month of August </li></ul></ul></ul><ul><ul><li>The sudden large rainfall caused flash flood at Louisville and area surrounding the Kentuckiana Region </li></ul></ul>2009 Kentuckiana Flash Flood - Causes
  7. 7. Case Study of Flash Flood (2) <ul><li>Environmental Effects of Flash Flood in Kentuckiana : </li></ul><ul><ul><li>  Water depth surpassed 4 feets in areas of : Downtown Louisville, New Albany, Jeffersonville, and Clarksville </li></ul></ul><ul><ul><ul><li>Most of the downtown area was underwater </li></ul></ul></ul><ul><ul><li>Creeks and Streams flooded many neighbourhoods </li></ul></ul><ul><ul><ul><li>Flash flood rendered many roads impassible  </li></ul></ul></ul><ul><ul><li>Rain Continued to 1p.m. on the day by which the ground has been saturated </li></ul></ul><ul><ul><ul><li>The water level dropped slower than usual due to this fact </li></ul></ul></ul>2009 Kentuckiana Flash Flood - Environmental Effect
  8. 8. Case Study of Flash Flood (3) <ul><li>Damange from Flash Flood in Kentuckiana : </li></ul><ul><li>  </li></ul><ul><ul><li>The University of Louisville was closed and evacuated due to rising water level </li></ul></ul><ul><ul><ul><li>The university sustained USD $15 million of damage from 5 campuses </li></ul></ul></ul><ul><ul><li>The main branch of the Louisville Public Library was under 90cm feet of water which destroyed ten thousands books </li></ul></ul><ul><ul><ul><li>$1 million of damag </li></ul></ul></ul><ul><ul><li>20,000 LG&E customers had power service disrupted in Kentucky   </li></ul></ul><ul><ul><li>Hundreds of homes received major water damage in both Indiana and Kentucky  </li></ul></ul>2009 Kentuckiana Flash Flood - Damage
  9. 9. Video of Flash Flood: <ul><li>Kellick Creek Flash Flood 10th Feb 2007: </li></ul><ul><li>http://www.youtube.com/watch?v=MIQrSH6LMgA </li></ul><ul><li>Grand Canyon: </li></ul><ul><li>http://www.youtube.com/watch?v=WqcuX5f6Tk0&feature=related </li></ul>