In the summer of 1993 the United States were faced with the most devastating flood that has ever occurred. Seventeen thousand square miles of land were covered by floodwaters in a region covering all or parts of nine states (North and South Dakota, Nebraska, Kansas, Missouri, Iowa, Wisconsin, Minnesota and Illinois). All large Midwestern streams flooded including the Mississippi, Missouri, and Kansas, Illinois, Des Moines and Wisconsin rivers. The Mississippi river was above flood stage for 144 days between April and September and approximately 3 billion cubic meters of water overflowed from the river channel onto the floodplain downstream from St. Louis.
There were 4 principal reasons why flooding was so extensive:
?The region received higher than normal precipitation during the first half of 1993. Much of the area received 150% of normal rainfall and some states received more than double their average rainfall.
?Individual storms dumped large volumes of precipitation that could not be accommodated by local streams.
The Mississippi river is divided into two parts. The Upper Mississippi runs from its source to Thebes, southern Illinois, where the Ohio River meets the Mississippi. The Lower Mississippi runs downstream from Thebes to the Gulf of Mexico. Flooding was confined to the Upper Mississippi because the river channel widens considerably south of Thebes, and the Lower Mississippi received lower than average inflow from tributaries. Discharge increases steadily as more tributaries add water to the river.
Some of the environmental damage the flood contributed to include: a lower oxygen concentration (below 2mg/L) was elevated and more widespread than usual along the Louisiana coastline west of the delta. This can be attributed to two main causes. First, the high river discharge introduced abnormal amounts of nutrients during the summer months, fueling plankton growth. Second, solar heating, resulting in a very stable water mass on the continental shelf, rapidly warmed the widespread low-salinity plume of river water.
The increased plankton biomass and the highly stratified water mass spoiled hypoxic conditions, which covered approximately, double the area that would be expected in the summer. The effects of hypoxic conditions on the productive Louisiana fishery had a highly negative impact, as did it on the benthic community west of the delta.
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.
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 thousand 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 public water supply was reconnected. Economic loses in Des Moines totaled $716 million.
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 nations coal, a third of its petroleum, and half its exported grain. Barge traffic was halted for two months; carriers lost about $1 million per day. Some power plants along the river saw their coal stocks diminish from a two-month supply to enough to last for 20 days.
Hundreds of miles of roads built on the flat, wide floodplain was closed. Flooding is estimated to have cost $500 million in road damage.
All in all, the flood resulted in damages worth over $10 billion plus $6.5 billion in crops. More importantly the flood cost the lives of 45 people, destroyed over 50, 000 homes and 75, 000 were evacuated.
People were either left homeless or were forced to leave their homes due to the risks of the flood. Half the counties in the nine states were declared federal disaster areas. This is the first step in becoming eligible for federal aid, including direct grants from Congress, Federal Emergency Management Agency (FEMA) and many other groups. The first steps taken after the flooding was to rebuild everything that had been destroyed and then to attempt to prevent the flood from ever repeating itself. There are two major ways that engineers have attempted to control the flow of rivers in the Mississippi basin:
1. Build levees or floodwalls to contain rising stream levels
2. Build reservoirs on tributary streams to store floodwaters for later release.
However, over 9,300 km of levees were damaged following the 1993 flood. St. Louis was protected by a massive floodwall. The wall developed a leak but held up over the length of the flood.
Only 10% of Midwest residents who lived in flood-prone areas had flood insurance prior to the flood. Over eleven million buildings are located in flood prone areas but only 19% purchased flood insurance (?People are stupid?).
The United States is an EMDC and hence can afford the costs of the damage. Evacuation can easily be completed because of the more luxurious resources available in an EMDC. There were special aid groups that were working non-stop to prevent the flooding, funded by the government. In an ELDC where these luxuries and money cannot be found it tends to cause much more deaths. It will demand more time for reconstruction in for example India than it did after the Mississippi flooding. The flood of 1927 in Mississippi caused over 200 hundred lives to be taken something that could be compared to an ELDC. The U.S. were prepared for a possible flooding of the Mississippi river which helped save many lives in 1993 even though most of the levees were destroyed they acted fast to prevent it. Preparation, which is what the LEDC?s are poor at achieving.
Since the first levee was built on the Mississippi in 1718, engineers have been channeling the river to protect farmlands and towns from floodwaters. But the question is whether the levees, damns and diversion channels actually aggravated the flooding. There are two schools of thought. One supports accepting that rivers are apart of a complex ecological balance and that flooding should be allowed as a natural event. The other argues for better defenses and a more effective control against rivers.