Urban flooding has become a serious problem in many parts of the world and will influence the way in which the cities grow in future. Global warming has induced major change in rainfall pattern, increasing flood risk in many cities (Guhathakurta et al.,2011). For many of the coastal cities in India, the contemporary design standards adopted for storm drainage design may no longer be able to prevent flooding for a changing rainfall pattern. For example, Mumbai region in India experienced highest rainfall in this century with 944 mm on 26–27 July, 2005 following which, it was suggested to increase the design rainfall intensity to 100 mm/h (Gupta, 2007). The flash floods of 26 July, 2005 in this financial hub of India brought its life to stand still with 409 lives lost and an estimated economic loss of Rs. 50 billion (Jenamani et al.,2006). There have been instances of heavy rainfall in the recent past
in this region viz: 375 mm on 5 July, 1975, 318 mm on 23 September, 1981, 478 mm on 10 June, 1991, and 346 mm on 23 August, 1997 indicating an increase in the frequency of high intensity rainfall. Frequent flooding instances in Mumbai especially