Every year, uncontrolled flooding in the Brahmaputra and Ganges river basins results in loss of life, damage to crops, dwellings and other properties, contamination of water supplies, the spreading of waterborne disease and disruption of orderly social and economic progress. Despite the building of barriers, dikes and levees to protect against flooding, major floods continue to cause extensive damage and prevent full utilisation of the land. Attempts to clear and maintain river channels, to assure the passage of water without obstruction, and to protect river banks and embankments with "river training works" have proven expensive and only marginally effective.
The future trend is likely to be one of increased flooding. Changes in the catchments beyond Bangladesh's northern and eastern borders — caused by deforestation and more intensive land use — are increasing the sediments carried by rivers and leading to bigger and bigger floods. Concurrently with the floods, the south-west monsoon winds raise the mean tide levels in the Bay of Bengal, reducing the slope and, hence, the rivers' discharge. Other factors which contribute to flooding are heavy rainfall, flat topography of the land, siltation of riverbeds and development of the flood plains.
It is clear that flooding is on the increase year by year. There was a severe flood in 1987, followed in 1988 by a flood of catastrophic proportions. It surpassed all previous records in terms of water levels and the extent of inundation (see Nov/Dec Himal). Almost three-fourths of the country, including Dhaka, went under water. Hundreds lost their lives, railways and roads were washed away, and the loss of major crops was nearly total. Bangladesh's economy was crippled.
While flooding in Bangladesh has long been viewed as a natural phenomenon, a combination of human factors appears to have created and exacerbated the country's vulnerability to flooding. Most experts consider that the major manmade cause is deforestation in the catchments of the major rivers lying in Nepal and India. The upstream developments, including the Farakka Barrage on the Ganges about 11 miles upstream from the border, also contribute significantly.