Detention Ponds for Managing Flood Risk due to Increased Imperviousness: Case Study in an Urbanizing Catchment of India

Abstract

Land-use change has been identified as one of the major factors responsible for change in runoff and therefore flood risk in urban areas. The present study quantifies the flood risk imposed as a result of increased imperviousness and different flood hazard–causing parameters. A 1-year flood hazard map was developed for Guwahati city of India, and the hazard ranks were developed by the interactive effect of hazard-causing parameters such as flood depth, inundated area, land use, affected population, and roads corresponding to the land use of 26 and 211. Based on the hazard ranks, further flood risk zones were identified. Flood depth and flooded area were found to be the most influential hazard-causing factors in deciding the overall flood risk of the area. Flood risk was found to increase with time from 26 to 211, and hence with increase in imperviousness. A detention pond was proposed to reduce the increased flood risk in the study area. A volume-based approach was adopted to fix the capacity of the detention pond. The maximum flood depth was found to be reduced by 46.5%, and the inundated area in the city was reduced by 43% as a result of the provision of a detention pond. Thus, detention ponds were found to be effective in reducing the effect of urban flood, and hence can be proposed as a suitable measure for flood management.