Ramifications due to urbanization and climate change on stormwater runoff and conduit efficiency: an integrated water management approach

Urbanization and climate change increase the frequency of urban floods worldwide which in turn poses a great challenge in the management of the urban stormwater drain system. This study investigated the impact of climate change and surface imperviousness in the urban stormwater runoff and the impact of washed off pollutants load in the conduit efficiency for two census wards Triplicane (ward 116) and Valasaravakkam (ward 152) in Chennai City. The climate change data for the study area wards were taken from the regional climate model (RCM) of Representative Concentration Pathway (RCP) 4.5. Storm Water Management Model (SWMM) with quality and quantity scenarios were developed and the results of the present year scenario were validated using a questionnaire survey. Intensity Duration Frequency (IDF) curves were generated to forecast the observed rainfall and climate model data for various return periods, i.e., 2, 5, 10, 50, and 100 years for future climatic scenarios (2030s and 2050s). The model results show that infiltration is only 3–7% of the total rainfall in the study areas and the maximum blockage and reduction in conduit capacity were estimated to be 65 and 40%, respectively. This paper presents the observations and suggestions for improving the conduit efficiency from an Integrated Water Management Approach (IWMA). HIGHLIGHTS Imperviousness of the study area was calculated based on LULC classification using Google Earth.; Bias correction was carried out for the climate data using observed rain gauge data.; Evaluation of the impact of pollutants load in the conduit carrying capacity using the SWMM.; Questionnaire survey outcomes were used to understand the past extreme events and also used in conjunction with the model outputs to derive suggestions.