Mississippi River Flood 1993
The flood of the river Mississippi river in April 1993 became known as the ‘Great flood’ and was one of the worst floods in the history of the USA, covering an area of 80,000km2 across 9 states, killing 50 people and lasting 6 months.
· The winter of 1993 saw heavy snowfall across the region.
· A particularly wet autumn in 1992 meant soil moisture levels were far above average in 1993.
· From April storms caused record rainfall levels across the Mississippi drainage basin as much as 750% above average in some places.
· Some scientists believe that the massive eruption of Mount Pinatubo in 1991 meant there was an increased amount of dust in the atmosphere across America, which caused increased cloud condensation, leading to heavier rainfall on the south west of the US, while the southwest suffered droughts and heat waves.
· The excessive hard engineering of the river has been blamed for exacerbating the flood as over 1000 levees failed and dams burst.
· Extensive urbanization of the flood plain reduced infiltration rates, increasing surface run off.
· Poorly constructed levees and other flood defenses.
· Nine states were affected. Floodwater stretched from Memphis in the south to Minneapolis in the north covering 23 million acres. 48 people were killed.
· Almost 70,000 people were evacuated from their homes.
· Final damage costs were estimated at $10 billion. Over 25% of this was crop losses.
· Some areas never recovered. The town of Valmeyer, Illinois, was abandoned after the floods and rebuilt on higher ground.
· The river was closed to traffic for two months - 15% of the USA's freight uses the Mississippi.
· 150 levees (embankments) collapsed under the pressure of water.
· Dams burst and bridges were closed. By mid July 100 tributaries had flooded and the Mississippi spread across the flood plain for 10 - 25 kilometers.
· Navigation on the Mississippi and Missouri was closed resulting in a loss of $2 million per day in commerce.
· 26.5 million sandbags were used in attempts to save areas from flooding.
· The Army National Guard and American Red Cross set up water stations to restore water supply.
· The Army rescued people from stranded locations using Engineer Corp barges.
· Civil Air Patrol crews from 21 states served more than 5,000 meals to flood victims and volunteers, and their pilots logged more than 1,500 hours in the air inspecting utility lines and pipelines.
· Over 1,000 flood warnings and statements, five times the normal, were issued to notify the public and need-to-know officials of river levels.
The management of the Mississippi has been mostly hard engineering carried out by the U.S. Army Engineer Corp, including river straightening, levee and dam construction and dredging. Many believe the floods to have been exacerbated or even caused by their over excessive management of the Mississippi by:
- Shortening the river, causing it to flow more quickly and increasing erosion.
- Restricting the flow of water inside levees, speeding up the flow and increasing the pressure on the levees and the likelihood of flooding. In 1993 a large number of levees broke or were too low to stop flooding.
- Altering the natural flow of the river to such an extent that the 1993 floods were the worst ever, even though there was less water in the river than during previous major floods.
- Increasing the energy in the river, because there is less sediment being moved around.
Engineers claim that the floods were a ‘one in a hundred’ event, which no defenses could have withstood and were not caused by the engineering works.
Channelization: This involves straightening, widening and deepening the river channel, so that it can carry more water, faster. It is criticized of increasing flooding as it results in water having a higher velocity and therefore more erosional power. A straight channel can also hold less water than a long winding one. This can involve massive costs and requires massive machinery, a task carried out by the Engineer Corp.
Levees: Another hard engineering strategy used along the Mississippi is Levee construction, this entails constructing or enlarging artificial or natural levees along the banks of the river to hold back flood waters. It is fairly cheap compared to channelization but still an unsustainable and labour intensive task.
The extensive hard engineering along the Mississippi is very un-sustainable, requiring vast amounts of materials, money and manpower to construct and maintain. Only the United States possesses the money, will, and ability (through the Army Engineers Corp) to carry out such an extensive project. It has also shown that massive amounts of money can not stop a river flooding and has promoted the argument that rivers should be left to their own devices and interfering with them can be very dangerous.