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Soil-environmental relationships on the Brahmaputra and Ganges floodplains in Bangladesh

ABSTRACT The reconnaissance soil survey of Pakistan 1961–71 produced important new information on the environmental relationships of soils on the Brahmaputra and Ganges floodplains in East Pakistan (now Bangladesh) which provided a sound basis for agricultural land use planning in the country. The greater part of the territory was found to have been formed in sediments deposited by tributary and distributary rivers, not by the two major rivers themselves. Piedmont, river meander, estuarine and tidal floodplain landscapes of different ages were recognised, with intricate relief and soil patterns with associated local differences in land use and crop suitability. In all except current active floodplain and piedmont fan areas, seasonal flooding was found to be mainly by rainwater ponded on the floodplains by high seasonal flood levels in the major rivers flowing into the country. Therefore, the country’s floodplains are not occupied, as is popularly believed, by sediments receiving annual increments of fertile alluvium; they are mainly occupied by soils developed to different degrees according to differences in sediment origin and landscape age, with profiles reflecting local differences in relief and drainage, and further changed by degradation through ferrolysis and by puddling of topsoils for rice cultivation.