Impact of missing flow on active inundation areas and transformation of parafluvial wetlands in Punarbhaba-Tangon river basin of Indo-Bangladesh

摘要

Punarbhaba river of Indo-Bangladesh has experienced hydro-ecological alteration after installation of Komardanga dam in 1992 and consequently wetland and inundation areas have undergone into transformation. The present work intends to explore the impact of flow attenuation on contemporary and upcoming flood extent and flood plain wetlands. In post-dam condition, average and maximum flows are attenuated by 36 and 41%, respectively, and as a result the active flood prone area is squeezed considerably by 39.72%. Average flood water depth is also reduced by 37.87% (4.45metre) after flow modification. Due to shrinkages of flood prone areas, wetland area is also reduced from 215.70 to 90.40 km(2) and larger part of the present wetland area is under stress and critical state. Predicted flood prone areas in next 25 years will be 328.91 km(2) and consequently 65.63 km(2) wetland areas may further be under hydro-ecological threats. Release of ecological flow is essential to restore and preserve the wetland.