ANALYSIS OF URBAN FLOOD AND ITS MITIGATION FOR GUWAHATI CITY

Abstract

Basin morphometric parameters play an important role in hydrological processes, as they largely control a catchment’s hydrologic response. In the case of ungauged, flash flood prone basis, their analysis becomes even more significant when studying runoff reaction to intense rainfall. Whenever the instrumental data becomes inadequate, Unit Hydrographs come under play in helping with estimating the runoff. In this work, instantaneous unit hydrographs based on the time-area method have been compiled along the drainage networks of the rural catchments in Guwahati. The city is located towards the South-eastern side of Kamrup district. The catchments drained by ephemeral torrents, have been subject to flash flooding during the last 3-4 decades, which caused extensive damages at the urban part of the Guwahati city. Hydrograph compilation in numerous locations along the catchments’ drainage networks directly reflected the runoff conditions across each basin against a given rainfall. This gave a holistic assessment of their hydrologic response, allowing the detection of areas where peak flow rates were elevated and therefore, there was higher flood potential. The resulting flood hazard zonation showed good correlation with locations of damages induced by past flood events, indicating that the method can successfully predict flood hazard spatial distribution. The whole methodology was based on geographic information system due to its excellent capabilities on storing and processing spatial data.