The floodplain ecosystem of Bangladesh covers about 80% of the total land area. Each year in Bangladesh, on average about 18% of the country is flooded. Different types of floods are responsible for this loss.
During severe floods, which occur from May to October, this percentage may increase considerably. All about different types of floods in Bangladesh and their causes, effects and possible solutions are mentions here in detail.
Different Types of floods and their causes
Floods are frequent in Bangladesh. They can be divided into four types:
- Monsoon floods
- Flash floods
- Rainfall-induced floods
- Tidal floods
Monsoon in Bangladesh generally signifies the rain from June to September or early October. Monsoon is the seasonal reversal of wind direction caused by the differential heating and cooling of landmass and oceans between summer and winter.
During the dry monsoon (winter), the wind blows from the north-east towards the sea, and during the wet monsoon (summer), it blows from the southwest towards the land. The summer monsoon winds bring an enormous amount of moisture, causing heavy rainfall in Bangladesh from June to September or early October.
During the army season, when the weather flow exceeds the holding capacity of rivers, canals, bells, and hairs, it inundates low-lying areas, causing damage to crops, homesteads, roads, and other properties.
Floods in Bangladesh are usually within tolerable limits. But occasionally they become devastating. Each year in Bangladesh, about 26,000 sq. km. (18%) of the country is flooded. During severe floods, the affected areas may exceed 55% of the total area of the country (May to October) by the three main rivers, the Ganges the Brahmaputra, Jamuna, and the Meghna.
The combined annual flood wave from this there river passes through a single outlet, the lower Meghna, and is too much for the lower Meghna to discharge into The Bay of Bengal.
The excess water cannot drain into the ground, and flooding caused by drainage congestion exists nearly everywhere except in the highland and hilly areas in the northern and eastern parts of the country.
The water increases and decreases suddenly, and flash floods generally occur in the valleys of hilly regions. They occur chiefly between April and May, usually in the northern and eastern rivers.
Flash floods are caused by a sudden onrush of water from upstream hilly areas, due to heavy rainfall in the catchment areas. A poor drainage system is also a major factor. These floods are really unpredictable and do not occur every year.
These occur during the monsoon season due to very heavy rainfall. These are usually localized and occur mostly in areas of poor drainage.
These are of short duration, the height of the water is usually 3 m to 6 m, and they block the inland flood drainage system. Tidal floods occur along with the coastal areas of the country and are accompanied by storm surges. The intrusion of saline water inland is a nuisance to most people living there.
Just as the case with cyclones, lives may be saved if people are properly warned and are evacuated from the affected area with their livestock before the flood occurs. If caught out when the flood does strike, people make temporary rafts out of bamboo and try to save themselves and their animals.
In such times, provisions food and clean water are scarce and people starve to death unless help arrives promptly. The lack of clean water causes water-borne diseases toe spread rapidly among the flood victims.
Flood control measures
In an attempt to reduce the devastating effects of floods, structures such as embankments and barrages have been constructed to hold back the water or to minimize the bank overflow. But there are some non-structural measures which are quite effective in controlling floods:
- Giving meteorological information to the people, so that they can be warned in time and evacuated to a safer place.
- and management to reduce surface run-off, which includes an intensive afforestation and reforestation program to increase the absorption of the water.
- change the use of the land in the flood-prone areas and the planting of flood-resistant crops.
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