Hydro-Morphometric Modeling for Flood Hazard Vulnerability Assessment of Old Brahmaputra River Basin in Bangladesh

Abstract

The present research introduces hydro-morphometric modeling to assess flood hazard vulnerability in old Brahmaputra River Basin in Bangladesh. Hydro-morphometric modeling is a spatial analysis in a GIS environment that has been applied for the estimation of flood hazard vulnerability. In this study the developed methodology processes information of seven parameters namely basin, flow accumulation, flow direction, stream order, stream length, stream density and drainage density. By applying Horton’s and Strahler’s formula of stream order, stream density and drainage density of old Brahmaputra River Basin are calculated. According to Horton’s stream density and drainage density reflects the runoff and discharge status of a basin which also revealed that basin having high stream density and drainage density is most vulnerable to flooding. The old Brahmaputra River Basin subdivided into five sub-Basin named as sub-basin A, B, C, D and E and their stream density are 1.318km-2, 1.113km-2, 1.2009km-2, 1.028km-2, 0.998km-2 and their drainage density are 0.713km-1, 0.690km-1, 0.689km-1, 0.703km-1 and 0.703km1 , respectively. Among the five sub-basins of this river basin, sub-basin A contains high stream and drainage density, which means this basin is most vulnerable to flooding, whereas basin C and D are least vulnerable because of its low stream and drainage density. Among the different floods, severe river flooding affects the area of 33.66 hectors agriculture land, 855.27 hectors fallow land, and 548.55 hectors vegetation cover, 275.22 hectors settlements and 177.3 hectors water bodies in this river basin. This study also revealed that agriculture land and resources, and life defence of marginal community of the Old Brahmaputra river basin are vulnerable to flood hazard.