Bangladesh is a land of rivers. It is prone to flooding due to being situated on the Brahmaputra River Delta (also known as the Ganges Delta )and the many distributaries flowing into the Bay of Bengal. Due to being part of such a basin and being less than 5 metres above mean sea level, Bangladesh faces the cumulative effects of floods due to water flashing from nearby hills, the accumulation of the inflow of water from upstream catchments, and locally heavy rainfall enhanced by drainage congestion. Bangladesh faces this problem almost every year. Coastal flooding, combined with the bursting of river banks is common, and severely affects the landscape and society of Bangladesh. 80% of Bangladesh is [floodplain], and it has an extensive sea coastline, rendering the nation very much at risk of periodic widespread damage. Whilst more permanent defenses, strengthened with reinforced concrete, are being built, many embankments are composed purely of soil and turf and made by local farmers. Flooding normally occurs during the monsoon season from June to September. The convectional rainfall of the monsoon is added to by relief rainfall caused by the Himalayas. Meltwater from the Himalayas is also a significant input.
Each year in Bangladesh about 26,000 square kilometres (10,000 sq mi) (around 18% of the country) is flooded, killing over 5,000 people and destroying more than seven million homes.During severe floods the affected area may exceed 75% of the country, as was seen in 1998. This volume is 95% of the total annual inflow. By comparison, only about 187 trillion l (1.87×1011 m3; 6.6×1012 cu ft) of streamflow is generated by rainfall inside the country during the same period. The floods have caused devastation in Bangladesh throughout history, especially in 1966, 1987, 1988 and 1998. The also affected a large portion of Bangladesh.
