Flooding is an overflowing of a body of water onto normally dry land. Flooding is one of the most widespread of climatic hazards and poses multiple risks to human health. The Mississippi river is in the USA which is an MEDC (more economically developed country. ) It is the second-longest river in the United States; the longest is the Missouri River, which flows into the Mississippi. Taken together, they form the largest river system in North America. If measured from the head of the Missouri, the length of the Missouri/Mississippi combination is approximately 6,270 km (3,900 miles).
The largest of many large tributaries on the river is the Ohio River. Bangladesh is between India and Myanmar. It is an LEDC (less economically developed country. ) The rivers of Bangladesh mark both the physiography of the nation and the life of the people. About 700 in number, these rivers generally flow south. The larger rivers are the Brahmaputra, the Meghna and the Ganges. They flow into the Bay of Bengal. 80% of Bangladesh is a huge flood plain and delta. It is flat, low-lying and easily flooded. Once the rivers overflow their banks the water can spread vast distances.
In 1993 the Mississippi flooded. Heavy rain in April 1993 saturated the upper Mississippi basin. Thunderstorms throughout June caused rapid surface run-off and flash floods. During July the thunderstorms increased in severity with one giving 180mm of rain in a few hours. By mid-July, the level of the Mississippi had reached an all time high. In 1988, Bangladesh flooded. The monsoon rains cause rivers such as the Brahmaputra and Ganges to overflow their banks between July and mid-August. Deforestation in Nepal and the Himalayas increases run-off and adds to deposition and flood downriver.
Human mismanagement has increased the magnitude and frequency of flooding by building on the flood plains (the process of urbanisation). A long period of heavy rainfall caused all three rivers to have their peak flow at the same time. The period of heavy rainfall coincides with that of the highest temperatures. High temperature accentuated by global warming melts snow and glaciers in the Himalayas. Poorly maintained embankments (levees) may leak or collapse. Building more levees upstream causes more of the discharge to reach the delta.
After the Mississippi flooded in 1993, it took several months for the water to drain off the land. Although the land was covered in fertile silt, the ground was far to wet for planting crops so land was useless for farming for many months. There were 43 deaths and cleaning-up operations took months. The contents of houses, factories and the buildings themselves were ruined. Boat traffic along the river had to be stopped. Where sewage had been washed into waterways, there was a threat of disease. Stagnant water attracted mosquitoes and rats. Insurance claims were high and numerous.
At the peak of the Bangladesh flood of 1988, it covered almost 70% of the country and affected 2/3 of the population. After the flood, only tops of trees and buildings could be seen. In the capital city Dhaka, the water was 2m deep and covered 3/4 of the city. The electricity was cut off for weeks and there was no safe drinking water. 7 million homes were destroyed and 25 million people were left homeless. There were shortages of food and medicine there were 1300 deaths. 2 million tonnes of rice was destroyed and 1/2 million cattle and poultry were lost.
The total cost of damages was $1. 5 million. To reduce flooding in Mississippi, 1000s of wing dykes and levees were placed along the whole river. St Louis was saved from flooding by a levee break. 200 dams and reservoirs were put in place. On the meanders, they made explosions to straighten and shorten the river, which was a waste of time and money because eventually the river returned to its original state. Afforestation, planting trees which delay run-off and reduce the amount of water reaching the river, is also being used.
To reduce flooding in Bangladesh, the Bangladesh flood action plan was introduced. 500 flood shelters will be built in the areas most at risk. These are cheap and easy to construct and would provide a place of safety for almost everyone. The flood forecasting system will be improved using satellite and computer technology. Flood disaster management plans which provide early warning and clear, effective instructions as to what people should do before, during and after a flood will be prepared.
Dams will be built to control river flow and hold back monsoon rainwater in reservoirs. These would be concentrated in Bangladesh but the plan would be extended to India and Nepal. The water would be used for irrigation and generating electricity but the cost could be more than i??500 million. The land will be divided into compartments and control water flow through a system of channels by sluice gates and water pumps. In the dry season, water would be moved to farming areas requiring irrigation.
Before the monsoon, water would be drained away to leave room for the flood waters. The embankments along all the main river channels will be completed to a height of up to 7m. More than 7500km of embankment is already in place, but repairs, heightening and new building would cost over $6 billion. This scheme should prevent serious flooding from river overflow. The USA is an MEDC, so they can afford to try out new ideas whether they succeed or not. However, Bangladesh is an LEDC, so everything must be thought about carefully or they will suffer from devastating debts.
In the US, the rescue services are well equipped and prepared, but in Bangladesh, they aren’t so well equipped and prepared. In the US, building levees and other things that prevent floods or reduce the damage they have caused, won’t take very long to build. But in Bangladesh, it could take up to 100 years. In the US, flood warning systems can be made public knowledge within a short amount of time because of newspapers and TV. However, in Bangladesh, not a lot of people have these things so it is harder for the public to find out the plans for their area.