A Study on Urban Flood Vulnerability in Vrishabhavathi Valley Watershed, Bengaluru, Karnataka using AHP, GIS and RS Techniques

Abstract

Urban flood problems are common in urban areas. These are due to heavy rainfall, adverse topographical conditions and anthropogenic factors, lead to destruction of drainage, damage to buildings, and even loss of life and property. To control such problems, systematic urban flood studies are necessary. The present study focused on the mapping and spatial analysis of urban flood vulnerability in Vrishabhavathi valley watershed, Bengaluru using AHP, GIS and remote sensing techniques. Some of the causative factors for flooding considered are rainfall, slope, drainage density, land use, building density, road density, non-existing natural drainage and non-existing Lake. Each thematic map of these factors was converted into raster maps. Numerical weight and ranking scores were assigned to each element factor according to fundamental scale of Analytical Hierarchy Process (AHP) technique. Urban Flood Vulnerability Zone (UFVZ) map was computed using weighted overlay analysis of GIS technique and classified into five categories, viz., very low, low, moderate, high and very high flood zone classes. UFVZ map was compared with the flood prone locations exist in Bengaluru city to assess the accuracy of result. Plot of flood prone locations on flood vulnerability zone map shows that, 50% of flood prone locations found under moderate flood vulnerability zone class and comparatively very less of flood prone locations 28% found in high zone class. The result depicts the fact that, urban flood vulnerability is highly influenced by anthropogenic factors than natural factors in urban environmental study area. The predicted flood vulnerability zones are found to be good agreement with known flood prone locations data.