General Information
Bangladesh is a heavily populated country. By 2050, it is expected to harbor some 220 million people. Most of the nation's acreage is flat and low-lying, prone to severe flooding and cyclones roaring in from the Bay of Bengal. Its landforms, while subdued, include one of the world's greatest mangrove forests.
Natural Causes
1. Bangladesh is located on the delta of two largest rivers of the Indian subcontinent. In total the whole country is surrounded by 3 main rivers. Heavy precipitation will cause all 3 powerful rivers to have a peak discharge at the same time.
2. Monsoon climate: Seasonal rainfall usually in the summer. The soil from the previous dry, hot weather will not be able to absorb a sudden pool of continuous precipitation. Lagtime will also immensely increase in a short period of time.
3. Tropical cyclones also often hit Bangladesh, bringing dense and heavy precipitation. This increases the discharge rapidly and cause costal flooding. Drainage density will shoot up combined with the monsoon rainfall, flooding is very likely to occur.
3. Melting of snow in the Himalayas results in heavy runoffs and soil erosion, and since most of the country consists of a huge flood plains and deltas, the drainage basin will easily overflow.
4. In terms of geography, 70% of land is less than 1 meter above sea level, 10% of the land is made up of lakes and rivers. Any slight rise in sea level can be an instant threat.
2. Monsoon climate: Seasonal rainfall usually in the summer. The soil from the previous dry, hot weather will not be able to absorb a sudden pool of continuous precipitation. Lagtime will also immensely increase in a short period of time.
3. Tropical cyclones also often hit Bangladesh, bringing dense and heavy precipitation. This increases the discharge rapidly and cause costal flooding. Drainage density will shoot up combined with the monsoon rainfall, flooding is very likely to occur.
3. Melting of snow in the Himalayas results in heavy runoffs and soil erosion, and since most of the country consists of a huge flood plains and deltas, the drainage basin will easily overflow.
4. In terms of geography, 70% of land is less than 1 meter above sea level, 10% of the land is made up of lakes and rivers. Any slight rise in sea level can be an instant threat.
Human Causes
Urbanization of floodplain
Urbanization perspective of Bangladesh. Source: AIA
One of the main human causes of the flooding in Bangladesh is urbanization of floodplain to house the rapidly increasing population in the country. The majority of Bangladesh is made of floodplain of the Ganges and Brahmaputa rivers, whereas the amount of lands positioned less than 6m above sea level exceeds over half of the country. The urbanization of these floodplains has increased the magnitude and frequency of flooding. As before the area is urbanized, rainfall can be infiltrated through soil and permeable rocks, which reduces the amount of water that directly enters the river. However, urbanization has caused to ground to be covered with impermeable substances such as cement, the rain is unable to infiltrate through the soil anymore. Thus, increasing the rate and scale of surface runoff.
Increasing population
A graph of Bangladesh's increasing population from 1901 to 2001.
The rapidly growing population in Bangladesh has also caused another problem, which is a huge demand of fresh water. 100000 new have been built to satisfy the demand, yet it results in the lowering of the water table, causing the land to sink 2.5 cm per year. This gradual craving in or sinking of the land area makes it more likely to flood.
Deforestation and irrigation
Deforestation in Bangladesh.
Source: O Level Bangladesh Studies
The deforestation in Nepal and Himalayas has reduced the amount of trees and plantation. As a result, there are less interception by tress and less evapotranspiration. The lack of trees elevates the rate and amount of runoff, meanwhile, increasing the amount of soil erosion as there are no tree roots to control the flow of water and holding the soil together. Moreover, the river also experiences changes due to human causes. The river Ganges has been diverted for irrigation purposes, this has removed sediments from the river’s load. Hence, it no longer builds up floodplain further downstream. Lastly, global warming which is occurs mainly due to humans has elevated the sea level, which adds to the amount of precipitation in Bangladesh.
Bangladesh in huge debt
The most dominant human cause of the flooding in Bangladesh, is the fact that Bangladesh is a less economically developed country and is in huge debt, therefore, the country is unable to provide flood protection measures. For instance, this has caused the lack of maintenance of embankments (levees), which as a result, experiences leakage and collapse in moments of high discharges. Moreover, there are also many existing flood defenses which fails to work due to lack of money the country has to keep them working. As private investors seeks for quick profits, there would not be long term investments in flood protection. The country needs to export n order to earn money, however, the money they have is used to support exports rather than building and maintaining flood defenses. The corruption within the country also further drains away money that could be used for flooding protection schemes.
The most dominant human cause of the flooding in Bangladesh, is the fact that Bangladesh is a less economically developed country and is in huge debt, therefore, the country is unable to provide flood protection measures. For instance, this has caused the lack of maintenance of embankments (levees), which as a result, experiences leakage and collapse in moments of high discharges. Moreover, there are also many existing flood defenses which fails to work due to lack of money the country has to keep them working. As private investors seeks for quick profits, there would not be long term investments in flood protection. The country needs to export n order to earn money, however, the money they have is used to support exports rather than building and maintaining flood defenses. The corruption within the country also further drains away money that could be used for flooding protection schemes.