Damming effect on habitat quality of riparian corridor

Abstract

• This work delimits multi-criteria based riparian corridor. • The riparian habitat quality was evaluated for pre and post HA phases. • The riparian zone was decreased by 12.29% in post HA phase. • The very poor riparian quality area has increased over time. • The riparian quality models were validated using ROC, wilcoxon signed rank test. Riparian corridor, a vital ecotonian ecosystem is under stress due to flow reduction and inconsistency of flow in Lower Tangon river basin across the neo tectonically active Barind tract of India and Bangladesh. But it is ill defined and its habitat quality is rarely assessed insipite of its immense socio-ecological importance. The present work intends to delineate the riparian corridor and quality assessment of the riparian habitat in reference to the hydrological alteration (HA) triggered by anthropogenic activities, mainly damming in 1989. The present work applied multi-parametric (altitude, topographic roughness, water body, forest patches) approach for delineating the riparian corridor instead of existing uni-criterion approaches for the same. Quality assessment of the habitat is done using nine surface, ecological, hydrological and anthropogenic parameters in the Arc Gis platform employing advance machine learning algorithms like Fuzzy logic (FL), Artificial Neural Network (ANN), Random Forest (RF), Random subspace, Dagging and Support vector machine (SVM). Total 20.63 km 2 and 18.36 km 2 areas respectively in pre and post-HA periods alongside the main river are identified as the riparian corridor. HA has reduced the area under the riparian corridor by 12.29% in post-HA state. Simultaneously, the quality of the riparian habitat is also deteriorated in the post-HA period. In pre-HA state, 49.05% area was under good to very good riparian habitat but it is reduced to 11.86% in post-HA state. Regularization of the flood, release of ecological flow to the downstream, renovation of tie channels between flood plain and river, restriction in agricultural invasion towards riparian forest and wetland are some of the essential steps for minimizing qualitative deterioration of riparian habitat and amelioration of the ecosystem concerned.