A Study on the Impact of Climate Change on Urban Drainage System

Abstract

Flooding risk due to heavy rainfall in urban areas, especially in Indian cities, is very high. Due to climate change, heavy rain has become a regular phenomenon. Flooding is the worst and most deadly natural disaster and has resulted in the death of millions and millions of people in the last century. In the last few decades, the frequency of high-intensity rainfall for a short period has considerably increased. Already most of the city’s existing drainage system is inefficient in draining the normal rainfall water, with the increase in rainfall intensity makingmakes the situation worse. In this paper, our primary focus is on two objectives. First, the urban flood due to heavy rainfall and increasing precipitation intensity due to climate change is analyzed. Second is the management of urban floods by using the Storm Water Management Model (SWMM). Herein, using the SWMM model, the present drainage infrastructure of Bhubaneswar City is examined. The rainfall intensity is evaluated using the IDF curve technique for future climate change precipitation data and historical data. Gumbel’s probability distribution is applied to estimate future return periods based on climate change data. The effectiveness of the existing drainage system of a part of Bhubaneswar City is evaluated, and the future flood problems due to extreme peak floods were analyzed. At last, the appropriate adaption measures for improvement in the drainage system are suggested. According to result out of 92 junctions 17 will be flooded during this high intensity rainfall condition. Junction No. 33 is most flooded point which flooded more than hour and maximum flooding time is 6 hours. After find out flooded location, Dimension of Channel increase by trial error method to counter the flood problem. In first outfall node (O1) average flow rate is 5.671 m3/sec, maximum flow is 9.219 and total volume is 82.14M liter. In second outfall node (O2) average flow is 10.874 m3/sec , maximum flow 16.944 m3/sec and total volume is 161.944M liter. The results show that time to peak and runoff peak is more in areas having impervious surface and dense population and length of conduits and rugosity coefficient are the prime factors governing peak flow. Rainfall analysis shows a annual rainfall is not considerably increase but the the rainfall intensity is increase considerably for a short period of time which occurs flood. This study approach is helpful to assess the future floods and guide policy makers for designing of adequate urban drainage system in that city.