The active delta of the Ganges‐Brahmaputra Rivers: Dynamics of its present formations

The present active delta of the Ganges‐Brahmaputra Rivers, drawing almost the entire flux of the great river system, is highly dynamic, with rapid migration of its channels and shoals. Erosion rate to the maximum of about 400 mlyear and vertical accretion rate over 3 mlyear were observed. However, neither the erosion site nor the erosion rate is constant in time. Similarly, accretion rates differ from place to place, with higher rates in the tide‐dominated areas. Short‐term comparison of cross‐section profiles indicates a general pattern of aggradation of northeastern channels and a degradation of southwestern channels, indicating a net southwestward migration. The pattern supports earlier observations in which a horizontal stratification of the delta area was found in distinct divisions of flood and ebb channels. With this trend of channel migration, the delta as a whole appears to be building up toward the southwest. However, it is also noted that some of these developments were accelerated by human interventions in the 1960s.

Keywords:

• Bangladesh
• channel migration
• coast
• delta
• horizontal stratification
• tide