Flooding in Louisiana Introduction Louisiana has problems with flooding. The Mississippi River borders the East Side of the state and often floods due to precipitation. Other for reasons flooding includes dam failure or land problems. The flooding has a major affect on the people in the state since they must. deal with the water and all of its damage. The scope of the problem is precipitation.
Hurricanes can hit Louisiana and cause flooding in the lower Mississippi. Also heavy rains often hit the state. "A slow moving weather system dropped large amounts of rain over northern Louisiana... ." (FEMA, Feb 1, 99). The amount of time in which rain falls is an uncontrollable factor causing the state to be well prepared for all types of flooding. Dams are a good way to help the flooding.
Flooding is an earth science related problem in Louisiana. Physiographic Province Louisiana lies in the Mississippi River valley and borders the Gulf of Mexico. The problem flooding areas are those closest to the Mississippi River and the delta. The other states that touch the river are Minnesota, Wisconsin, Iowa, Illinois, Missouri, Tennessee, and Arkansas.
New Orleans is a city that is very vulnerable to flooding because much of the city is below sea level. The below sea level parts of the city must be keep dry by constantly pumping water into the Mississippi or to the sea, otherwise those areas would flood from groundwater alone. Even the portions of New Orleans that are not below sea level are a part of the vast Mississippi flood plain. Flood plains are places where rivers flood during normal conditions.
Dam-like ridges form along the banks of rivers on flood plains and under normal conditions keep the river in its channel. During floods rivers flow over the tops of levees and flood the flood plains that lie adjacent to the river channel. Man has constructed channel walls to 'beef up' the natural levees to protect the flood plains. However, all of New Orleans and the flood plain beyond the city is constantly threatened by flooding of the Mississippi River (Mads i, July 99). Flooding A flood is a temporary overflow of a river onto adjacent lands not normally covered by water. Causes for flooding include higher than normal amount of precipitation.
Furthermore, cooler than normal temperatures can make the ground cold so there is less evaporation of water (NSC, February 98). Rainstorms are short periods of very heavy rain that fall over a small area. They can cause flash floods, as rivers become torrents (Wood). However that may soon change.
The National Weather Service is responsible for predicting the weather and warning people about severe weather. Up until now, meteorologists could only guess when a flash flood would occur. Now, they have a new tool, called Doppler radars, which can track rainfall street by street. This should provide more accurate flash flood warnings across the country. The new radar systems should allow meteorologists to provide warnings before a flash flood occurs (PBS). In any given stream, river, or watershed, annual flood pulses may be common, but large-recurrence intervals, major flood events are rare (Michener).
Precipitation Exceptional precipitation makes the Mississippi River flood in Louisiana. Usually when combined with several other factors and exceptional precipitation flooding occurs. The coast floods due to hurricanes and high tides. Global warming can also cause the seat to rise on the coast.
Streams A stream channel is the conduit for water being carried. The volume of water passing any point on a stream is called the discharge. When the discharge becomes to high, the stream widens its channels by overtopping its banks and flooding the low-lying areas surrounding the stream. Straight channels are rare; they are relatively straight in direction. Meandering channels were straight at one time. They migrate back and forth on the flood plain.
Braided channels have islands and bars in them. Deltas and drainage systems A delta is when a stream enters a standing body of water (Fig 1). They build outward from the coast. Drainage systems develop in such a way as to efficiently move water off the land. Each stream in a drainage system drains a certain area, called a drainage basin. Figure 1, Delta In a single drainage basin, all water falling in the basin drains into the same stream.
Drainage basins can range in size from a few km 2, for small streams, to extremely large areas, such as the Mississippi River drainage basin, which covers about 40% of the contiguous United States. (Fig 2) These are types of drainage patterns (Nelson, March 2000). Figure 2, Drainage PatternsErosionStreams erode because they have the ability to pick up rock fragments and transport them to a new location. The size of the fragments that can be transported depends on the velocity of the stream and whether the flow is laminar or turbulent. Turbulent flow can keep fragments in suspension longer than laminar flow.
Streams can also erode by undercutting their banks resulting in mass-wasting processes like slumps or slides. When the undercut material falls into the stream, the fragments can be transported away by the stream. Streams can cut deeper into their channels if the region is uplifted. As they cut deeper into their channels the stream removes the material that once made up the channel bottom and sides. Levees Natural levees are constructed as a result of flooding, but natural levees tend to be relatively low and do not offer much protection from large discharge because they can easily be overtopped.
Human made levees, such as those on the Mississippi River, are much higher and are constructed to prevent flooding from high discharges on the River. Most levees are constructed of piles of dirt with a concrete cover on the riverside of the levee. Such levees often give a false sense of security for those living on the flood plain. The levee was built to protect, because failure of such levees can lead to flooding, either because discharge can become great enough to overtop the levees or the levees can become weakened and fail (Nelson, March 2000). The levees are constructed by the federal government and are maintained by local interests, except for government assistance as necessary during major floods. Periodic inspections and maintenance are made by personnel from the U.
S. Army Corps of Engineers and from local levee and drainage districts, as it is essential that the levees be maintained in good condition for their proper functioning in the flood control plan (Fig 3) (US ARMY, June 99). Figure 3, Flood Control Flooding damage Nearly fifty people died as a result of the flooding of The Mississippi River in 1993. This is the River at two different times (Fig 4 and Fig 5). Fig 4, Upper Mississippi River in July, 1992 Fig 5, Upper Mississippi River in July, 199326, 000 people were evacuated and over 56, 000 homes were damaged. Economic losses that are directly attributable to the flooding totaled $10-12 billion.
Indirect losses in the form of lost wages and production cannot be accurately calculated. The consequences of flooding were determined by land use patterns. The greatest economic losses occurred in cities on the floodplain. Des Moines, Iowa, located in the center of the flood region, became the largest U. S. city to lose its water supply when its water treatment plant flooded.
More than 250, 000 people lost drinking water for 19 hot summer days. Water pipes, contaminated by floodwaters carrying sewage and agricultural chemicals, had to be flushed out before the municipal water supply was reconnected. Economic losses in Des Moines totaled approx i mat ely $716 million. The flooding submerged eight million acres of farmland. Production of corn and soybeans were down 5-9% as a result and corn prices rose by $0.
15 per bushel. Floods deposited thick layers of sand in some fields. The U. S. Soil Conservation Service spent $25 million to buy flood-prone farmlands for conversion to natural conditions (e. g.
wetlands). Conversion of natural lands to farmlands has resulted in greater run-off and exaggerated the effects of flooding. Modern farming methods leave plant residue on the surface and reduce run-off. The Mississippi River itself is a crucial part of the Midwest's economic infrastructure. Barge traffic normally moves goods through a system of 29 locks between Minneapolis and St. Louis.
Barges carry 20% of the nation's coal, a third of its petroleum, and half it exported grain. Barge traffic was halted for two months; carriers lost an estimated $1 million per day. Some power plants along the river saw their coal stocks dwindle from a two-month supply to enough to last just 20 days. Hundreds of miles of roads built on the flat, wide floodplains were closed. Flooding is estimated to have cost $500 million in road damage (NSG, February 98). Flooding costs The increasing cost of flood damage, from one billion dollars in 1932 to five billion dollars in 1997, has little to do with precipitation, say atmospheric researchers.
Roughly half the rise is caused by population growth, the rest by higher property values, according to the National Center for Atmospheric Research in Boulder, Co (Popular Mechanics). How the Mississippi River Changes The Mississippi River is one of the most heavily engineered natural features in the U. S. The character of the floodplain has changed to accommodate agriculture and urbanization.
Approximately 80% of the original wetlands along the river were drained since the 1940's. Wetlands act as natural storage reservoirs for floodwaters. They absorb water during heavy precipitation and release it slowly thus reducing run-off to streams and decreasing flood volumes. The river channel itself has been artificially constrained by levees and flood walls. These structures serve to increase the volume of water that can be held in the channel and in turn increase the size of the flooded area if the levee breaks (NSG, February 98). Dams Dams occur as both natural and human constructed features.
Volcanic events, landslides, or blockage by ice create natural dams. Human constructed dams are built for water storage, generation of electrical power, and flood control. All types of dams may fail with the sudden release of water into the downstream drainage. Stabilization and protection of the riverbanks are important to the flood control and navigation plan, serving to protect flood control features and to insure the desired alignment of the river's navigation channel. This is accomplished by: cutoffs which are used to shorten the river and reduce flood heights, revetment is to stop the river's meandering, dikes are used to direct the flow, and improvement dredging to realign the channel (US ARMY, June 1999). Floods serve functions Floods also serve important functions, according to U.
S. researchers Timothy Wootton, Michael Parker, and Mary Power. The three scientists studied the caddis fly, an insect that lives in the western United States. When caddis flies are larvae young, immature insects that differ from adults in structure and way of life they inhabit river bottoms. There they gobble up algae, often to the point that they deprive other insects of algae. Those other insects often serve as a vital food source for fish.
Without those other insects, fish do not get enough to eat, and they starve. The scientists say a flood can be good news because floods dislodge river rocks, which crush caddis fly larvae on the river bottom. The result: fewer caddis fly larvae, more algae for other insects to eat, and more food for fish. The scientists believe that fewer floods on dammed rivers have led to a decline in salmon populations in the Pacific Northwest. Occasional deliberate flooding of those rivers may be required to keep salmon populations healthy (Current Science). Figure 6, DredgingProjectsThe National Wildlife Federation is using the federal government to stop unnecessary dredging of the Big Sunflower River in the Mississippi Delta, a project that would ravage one of the most biologically rich areas in the nation (Fig 6).
The Big Sunflower and its tributaries comprise one of the few remaining river systems in the Mississippi Delta not already severely altered by flood-control projects. The proposed dredging and clearing would wipe out thousands of acres of bottomland hardwood wetlands taking a huge toll on fish, waterfowl wintering grounds, and freshwater mussel beds (International Wildlife). Floods cause disasters, but they can also be beneficial. Whenever a river overflows its banks, it dumps sand, silt and debris that it has carried downstream onto the surrounding land. After the floodwaters move away the soil is more fertile, because of the organic matter and minerals in this material. That is as long as there's not too much sand (NOVA).
Flood Preparation There are ways to be prepared for floods. Always keep the gas tank of your car at least half full. Also do not drive where water is over the roads. Parts of the road may be washed out. It is very important to keep a battery-powered radio tuned to a local station and follow emergency instructions. It is a good idea to be prepared to evacuate before the waters reach your property (Be Prepared).
Virginia Virginia has some flooding problems; however, they are not nearly as bad as the Mississippi. Virginia has smaller rivers and less precipitation. There are other states with major and worse flooding. These states are all bordering the Mississippi river.
Conclusion Flooding is a major problem in Louisiana. They have ways to help the flooding and control it. Also, experts know a lot about the river so things can be handled well. Though the amount of precipitation cannot be controlled it is handled well.
Flooding In Louisiana Christy Maddox Earth Science Mr. Won June 2, 2001 References Cited " Be Prepared, Cautious If Storm Spawns Flooding" September 1998. web Donald. Flooding in New Orleans. July 1999. web "Flood Costs.' Popular Mechanics.
Jan 2001. Vol. 178. Issue 1. p 29.' Floods have their benefits.' Current Science.
09/11/98. Vol. 84. Issue 1. p 12." The Hows and Whys of Floods" April 2001. web World Book.
World Book. Chicago. 2000. Michener, William K. and Hae uber, Richard A.
, Bioscience. American Institute of Biological Science. Sep 98. Vol. 48. Issue 9.
p 677." The Mississippi River and the Tributaries Project," June 1999. web "Mississippi River Country USA," January 2001. web "Mississippi River Flood: 1993," NSG, Feb 24 1998. web Flood. Nelson, Stephen A. River Flooding.
March 2000. web Stephen A. River systems and causes of flooding. March 2000.
web 'NW sues to halt dredging project in Mississippi's Big Sunflower River.' International Wildlife, Mar/Apr 99, Vol. 29 Issue 2, p 6." What's Good About a Flood?" April 2001. web Jenny. Storms.
World Book. Chicago. 2000.