Climate Change and Its Impact on Surface Runoff Characteristics of an Urban Catchment

Abstract

Flooding can occur naturally due to heavy rain, exceptionally high tides, snowmelt, or human-made causes such as dam break, breach of river embankment, and so on. Urban flooding and its associated fury have become very common in the recent past. The combined effects of urbanization and climate change have increased the risk of flooding in cities that can be attributed to various factors. The urbanization causes imperviousness of the surface due to more built-up areas, which lead to reduced infiltration, thus, an increment in the surface runoff. Climate change has affected the quantity, intensity, and frequency of precipitation, which made the urban catchments more vulnerable to flooding. The present study aims to investigate the potential impacts of climate change on the surface runoff characteristics of an urbanized watershed. The future climate scenario corresponding to the study area was obtained from global climate models (GCM) that has shown superior performance in forecasting the future climate. As the GCM outputs are for a larger grid, they must be downscaled to the local/regional scale to obtain the corresponding climatic variables. In this study, we have used the delta change method of downscaling. Further, the runoff was simulated using the stormwater management model (SWMM), considering the future scenario. The results from precipitation analysis indicate an increase in precipitation in the future. Consequently, the simulated runoff has shown an increment in the number of flood events in 2025, 2050, 2075, and 2100. The present study has also found that the continuous rainfall simulation was resulting in an underestimation of the urban runoff. Therefore, for urban applications, event-based runoff simulation would be a better choice for characterizing the future urban flood events.