5-Urban Flooding and Drainage.

Abstract

Urban flooding is a result of the decision of urban communities to provide only partial protection from flooding in the cities. The location of urban communities in relation to large rivers, sea and drainage networks of rural basins is another important factor contributing to urban flooding. Urbanization increases peak discharge, reduces response time and base length of the unit hydrographs. This in turn reduces the level of protection, which was provided at the time of laying down the drainage network wherever urbanization has occurred in upstream areas. The net effect of the increased urbanization is increased flooding unless the capacity of the existing network is increased. The most important management function is to ensure that the drainage network is free from silting and all portions of the network are maintained as per design specifications. Once the infrastructure is in position, flood depth frequency maps need to be developed for involving and educating the people about the dangers of flooding, identifring trouble spots and developing local solutions for providing additional drainage. Scientific analysis for achieving these goals require static data about the system, spatial and temporal distribution of rainfall in the urban area and simulation models.