Exploring the forms of wetland modifications and investigating the causes in lower Atreyee river floodplain area

Abstract

The current study focuses on the various kinds of external and interior hydrological and morphological modifications of wetlands in the lower Atreyee river basin of India and Bangladesh. The relevant eight diverse causes were carefully investigated adopting various approaches such as consistency scaling, change detection, landscape fragmentation, and 2D floodplain modelling. As per the results, only 274.79 km2 (2019) of wetland area is now available. A total of 650.04 km2 of wetland area has been changed to other land uses in last 30 years and 106.97 km2 of consistent wetland area has been turned into inconsistent. Reduction of the depth of water (77.09%) can be easily identified by NDWI intensity. Integrated large core wetlands have become fragmented into small patches increasing edge area ratio. Agricultural and built-up area expansions have been identified as the most important causes contributing to wetland conversion. According to the findings, 292.51 km2 of wetlands have been replaced by agricultural land, with an additional 99.44 km2 taken up by built-up area. Besides that, the construction of a dam across the Atreyee river has decreased maximum and average flow by 37% and 66.86%, respectively, which in turn has reduced overall flood frequency and the lateral flood extent of inundation areas (1627.3 km2 or 15.97%). As a result, 231.23 km2 wetland area in stress state is now left beyond the present active flood limit. Disconnection of drainage networks, groundwater-lowering, embankment of rivers, extension of infrastructure etc. are some of the other crucial causes of wetland transformation and loss. This study will undoubtedly be beneficial to decision-makers in their efforts to take a significant step towards conserving the wetland landscape, as well as to environmental preservation.