9. Estimation of Bank Erosion of the Haora River and Proposition of Bank Erosion Vulnerability Zonation Model

Naturally bank erosion is a severe problem to any fluvial system. The Haora River is also experiencing severe bank erosion in several parts of its course. Thus the BEHI model has been selected and applied in 60 spots (both left and right banks) along the Haora River (within its Indian territory) as the standard method for estimating bank erosion. From the estimated data, it is found that among the 60 spots, 8 spots are falling in very high erosion category, 13 spots in high category, 22 spots in moderate category, 11 spots in low category and 6 spots in very low category of erosion rate. Finally this method is compared with field generated erosion data, and it is found that models’ accuracy level is exact in 55 % cases, but the result of this model is acceptable for 76.7 % cases.

In this thesis, a new RS- and GIS-based method has been proposed for preparing bank erosion vulnerability zonation. This zonation can be done by estimating eight parameters, i.e. (i) rainfall erosivity, (ii) lithological factor, (iii) slope of the river bank, (iv) meander index of each curve of the river, (v) river gradient (longitudinal), (vi) soil erodibility factor of the bank, (vii) vegetation cover of the bank and (viii) anthropogenic factor which are present across the river. By superimposing all the six individual parameters (the first two parameters are constant for that particular basin), bank erosion vulnerability zonation map has been prepared for the Haora River basin. This method has been compared with the BEHI–NBS method, and it is found the values of both these methods are matching in the case of 31 spots. But there are only five spots, where the values of both the methods are completely different.