In recent days, significant flooding has been occurring along the Mississippi River. These dangerous high water levels are now reaching the South, with record water level forecasts for Arkansas and Mississippi, according to the Associated Press. We hear about drastic measures being taken by the U.S. Army Corps of Engineers blowing up a levee to save the town of Cairo, Ill. Here are some facts about the flooding and actions to mitigate the damage:
What causes river flooding?
The natural river channel can only handle a certain rate of flow without an increase in height. If the rate of flow into a section exceeds the outflow rate, the level will rise and may eventually overflow the natural riverbank.
The rate of inflow is determined by the amount of water coming in due to rain and snowmelt in the upstream portions of the river basin. The rate of outflow is determined by the depth and shape of the river channel. Recent heavy spring rains and high snowfall have created the extremely high inflow rates, according to OurAmazingPlanet.
Why did the Corps of Engineers blow up a levee?
The plan to intentionally breech a levee near New Madrid, Mo., was part of a contingency plan put in place long ago to allow flooding of farmland to prevent flooding in more populated areas. This was part of the flood control plan put in place after the historic floods of 1927. This plan includes the designation of four such floodways along the river which can be intentionally flooded when conditions require.
How is the height of the river specified and what is meant by river stage?
The height of major rivers in the United States is continually monitored by sensors called river gages. The current readings of these gages can be found at RiverGages.com. The river height is specified as the height over a reference elevation which differs by location. This is called the river stage, and for each location river stage readings corresponding to flood levels are noted.
What is the Corps of Engineers' role?
The Army Corps of Engineers mission is to "Provide vital public engineering services in peace and war to strengthen our Nation's security, energize the economy, and reduce risks from disasters." Through its Mississippi River Division, the Corps develops and implements plans for control of flooding along the Mississippi River; improvement of navigation; and preservation, restoration, and enhancement of environmental resources. This Vicksburg district website contains up-to-date information about the current flood conditions and steps being taken, with a special section on Flood Fight 2011.
Is this record flooding due to climate change?
Many scientists think that climate change will increase the number and intensity of storms. Although any single storm or flood event cannot be attributed to climate change, an increasing trend may be. This seeming paradox requires understanding the difference between weather and climate.Sources:
US Army Corps of Engineers Vicksburg District http://www.mvk.usace.army.mil/Associate Press on Yahoo News:
http://news.yahoo.com/s/ap/20110505/ap_on_re_us/us_severe_weather_flooding_167
http://news.yahoo.com/s/ap/20110504/ap_on_re_us/us_severe_weather_flooding_136
RiverGage.com http://www.rivergages.com
National Weather Service River Forecast Center http://www.srh.noaa.gov/lmrfc/?n=introductiontohydrologyforteachersandstudents
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