Droughts and Floods

1. Droughts and Floods Sarah Terhune, Drita (DM) Marku, and Samantha Pleasants

2. Droughts

3. Droughts • Drought-A period of abnormally dry weather sufficiently prolonged for the lack of water to cause serious hydrologic imbalance in the affected are. • Droughts can cause many issues like crop damage, water shortages. • During a drought after a while, people have to stop washing cars, watering the grass, and conserve water in other ways.

4. Droughts; Can be defined as: • meteorological- measure of the difference of precipitation from normal precipitation. A drought in one location of the country may not be a drought in anotherbecause of climatic differences • Agricultural-a situation where the amount of moisture in the soil is not enough for the needs of a crop. • Hydrological- surface and subsurface water supplies are below the normal level. • Socioeconomic-when physical water shortages affect people.

5. Drought • In the Horn of Africa the 1984–1985 drought caused a famine that killed 750,000 people. • A drought in the U.S. during 1988 led to the loss of $40 billion

7. Floods

8. What is a flood? • A flood is an overflow or accumulation of an expanse of water that submerges land.In the sense of flowing water, the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its normal boundaries

9. Flood Control • A levee is a natural or artificial slope or wall to regulate water levels. • A bund wall, is the area within a structure designed to prevent inundation or breaches of various types. • A reservoir is an artificial lake used to store water. • Low head dam, is a small overflow-type dam commonly used to raise the level of a river or stream Reservoir

11. Types of Floods • Riverine: Slow riverine floods are caused by runoff from rain or rapid snow melt that exceeds the capacity of the river. Causes include heavy rains from monsoons, and hurricanes; Slow riverine floods are flash floods resulting from intense thunderstorms or sudden release from an reservoir created behind a dam, landslide, or glacier. • Estuarine floods :These are commonly caused by a combination of sea tidal surges caused by storm-force winds. (A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category. )

12. Types of Floods (continued) Catastrophic floods: A catastrophic flood is caused by an unexpected event i.e. dam breakage, or as a result of another hazard such as a volcanic eruption or earthquake. Muddy floods: A muddy flood is created by run off on land. A muddy flood is produced by a collection of runoff . Sediments are then detached by runoff and carried as suspended matter /bedload. Muddy runoff is more likely detected when it reaches inhabited areas. Coastal floods: Coastal Floods are caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.

13. Effects on the Climate • “A warming planet also means snowy regions become rainy. People who live near rivers could see more flash floods: Melting snow slowly trickles into rivers, but rain can dump large amounts of water all at once.” (Source) • The warmer the oceans get and the more the ice caps melt, the higher the ocean will rise. This will lead to more flooding around coastal areas. • Melting from the Greenland ice sheet and the Antarctic ice sheet combined is estimated to account for about 14% of observed sea level rise. If the Greenland ice sheet melted entirely, sea level would rise 20 ft around the world.

14. Useful Links • http://www.dartmouth.edu/~floods/Archives/GlobalFloods1985-2006.gif • http://www.wrh.noaa.gov/tfx/hydro/FAW/fawmain.php?wfo=tfx

15. Sites Used • http://www.agu.org/pubs/crossref/1998/98WR01474.shtml • http://www.npr.org/templates/story/story.php?storyId=18022014