An increased amount of precipitation can also cause flooding. An above normal monsoon downpour in the Ganges-Brahmaputra-Megna drainage system is thought to be the primary cause of the 1988 flood in Bangladesh. It is not known, however, if the heavy precipitation is actually an effect of other processes such as the greenhouse effect or destruction of forests in the upstream region.
Another physical cause of flooding in Bangladesh is tectonic activity. The Indian Plate is moving towards the Eurasian Plate. The land where they meet (Himalayas) is getting higher and steeper every year (fold mountains). As a result soil is becoming loose and is susceptible to erosion. This causes more soil and silt in rivers, leading to flooding in Bangladesh as the river channel becomes narrower and shallower. As the young mountains continue to raise this means that the majority of the water will fall downstream taking as much as possible of the water into the river Ganges, the Brahamaputra and the Meghna.
There are also human causes in Bangladesh which are increasing the potential for the river Ganges to flood. These causes include excessive urbanization in Bangladesh. As rapid population growth creates extra pressure on the land of already overcrowded Bangladesh. Agricultural lands give way to housing developments and roads. This rapid development and urbanization have aggravated the flooding problem in Bangladesh. Prior to urbanization there is a greater lag time between intense rainfall and peak stream flow. After urbanization the lag time is shortened, peak flow is greatly increased, and total run-off is compressed into a shorter time interval favorable conditions for intense flooding.
Another human factor contributing is the fact that population in this country is continuing the increase, i.e. Nepal. In Nepal population increase means there is a greater demand for food, fuel and building materials. As a result deforestation has increased significantly. This reduces interception and increases run-off, which leads to soil erosion. River channels fill with soil and the capacity of the River Ganges and Brahmaputra is reduced and flooding occurs.
The failure of river management is another human factor increasing the chances of the river Ganges and Bramaputra to flood. Before the floods of 1987-8 the Bangladesh government proposed and carried out the ‘Flood Action Plan’ which used embankments (man-made levees) along the length of the main rivers. The aim was to have controlled the distribution and speed of flooding. However the embankments were not designed to cope with the amount of flood water in the 1987-8 floods. Breaches in the embankments resulted causing wide spread flooding. Critics argue that by trying to control them can lead to worse affects than if they were never built at all.
Another problem with these embankments was that they did help to hold access water in the river however also prevented rainfall getting into the rivers. As a result the land became to saturated and access water stayed on the land.
When discussing about coastal flooding it is important to recognize that it has both positive and negative consequences, the positive consequences may not seem to be too obvious but the majority of the subsistent farmers and the dwellers living in Bangladesh rely on floods for survival. Regular annual flooding is essential for people who live on the flood plain of these rivers, the farming season is planned around the floods, rice is a main crop and requires large quantities of water. Another advantage of flooding is that when the river floods it leaves behind fertile silt. The Monsoon flooding in Bangladesh is necessary for the maintenance of agriculture.
Floods also have extremely disastrous consequences. In August-September 1988 Bangladesh experienced an unpredicted flood causing loss of 1,657 human lives. The flood covered 80% of the land, 7 million homes were destroyed, 25 million people made homeless. A quarter of the rice crop was destroyed and 35 million people faced the prospect of starvation. Thousands of kilometers of road were flooded. The destruction of communication network meant it was impossible to deliver food and medical supplies. The rapid runoff caused soil erosion. Spawning grounds for fish and other wildlife habitat were destroyed, water was also contaminated which caused diseases to spread.
Furthermore according to reports people who live in perennial flooded zones have low indicators in all sectors of health, nutrition and education. Floods also contribute to the concentration of landownership due to distress sale by the poor in the post-flood situation to the cash heavy people. This is observed in all areas subject to natural disasters. They seem to serve as a disproportion factor in society.
Bangladesh is one of the worlds most poorest of countries, this means it can’t spend huge amounts in protecting the river from flooding. However the Bengali government has introduced some effective ways to prevent the river from flooding. Dams and lakes have been built up the river in India, this is thought to help prevent flooding by reducing the water flow into Bangladesh from everywhere else. Another way Bangladesh has tried to prevent the river from flooding is by planting mangrove swamps off coast to increase the amount of land that makes storm surges, i.e. it works by reducing their energy. Embankments have been built to protect the coast - more importantly, they have been maintained. Large concrete shelters have been built above flood levels to protect people (they are strong enough to withstand strong winds). An efficient early warning system has been organized, which includes a siren systems, and a leaflet drop using airplanes announcing the impending threat, however, it is unlikely that these things can be maintained by the Bengali government due to both its instability and the countries chronic lack of money.
The Ministry of Disaster Management and Relief has strengthened its emergency operations centers to collect and disseminate flood related information to be more prepared. The Government has implemented relief operations and the available food stocks are expected to meet emergency needs of the affected people for a period of two to three months. The Department of Agricultural Extension is taking steps to assess the needs for seeds and other agricultural inputs to support the farmers to meet post-flood requirements, and The Bangladesh Red Crescent Society (BDRCS) has been working with local authorities to provide urgently needed relief assistance to flood victims.
A plan called ‘Bangladesh Flood Action Plan’ (FAP) has also been introduced which tried to control the impact of the river flooding. The main features of this plan include:
- 5000 flood shelters built on stilts in areas most at risk
- Improved flood forecasting system using satellite and computers.
- Build dams to control river flow and hold back monsoon rain water in reservoirs
- Complete and strengthen embankments along the main river channels to a height of up to seven meters.
Other proposals have also been made, however the problem surrounding these proposals is that the poor local people wouldn’t be able to adapt quickly to the changes made. Bangladesh is low-lying and to make sufficient changes there isn’t enough money. If for example the course of the river is changed it will only cause further problems some where else. People in Bangladesh aren’t educated enough to build any appropriate flood protection and to maintain them.
The problem concerning Bangladesh is that most of the land is only a few feed above water and very unstable. No amount of river control can change this. To alleviate the impact of flooding Bangladesh’s only choice has to be severe population controls to reduce the density of people on this land and also to encourage a movement away from the lowest lying areas.
It is also believed that Bangladesh will each year run a three-times higher risk of suffering an exceptionally wet monsoon compared with the probability today, thus it is also expected that parts of Bangladesh face the risk of more frequent, major floods in the latter half of this century because of global warming.
