SENSITIVITY OF STORM WATER MANAGEMENT MODEL TO ITS INPUT VARIABLES

Abstract

Hydrology of urban areas is dominated by impervious surface and presence of manmade drainage channels. Engineering objective when dealing with urban hydrology is to provide for control of peak flows and maximum depths at all locations within the drainage system. Storm Water Management Model (SWMM) is a rainfall runoff simulation model which can be used for single event or long-term (continuous) simulation of runoff quantity primarily from urban areas. In the present study, only runoff component and routing portion of the SWMM5.1 have been explained and applied. This is the latest version of software which has been downloaded from internet. In this study, a practical application of SWMM has been demonstrated using the data of an industrial area located in Coastal District Pudimadaka of Andhra Pradesh State, India. Then sensitivity analysis has been carried out for various model inputs/variables/parameters. For the sensitivity analysis, the catchment is sub-divided into 45 number of sub-catchments. These areas have their different land use conditions which divert the runoff through open rectangular channels to outfalls provided across the boundary of the study area. Results obtained through this software are used for designing the storm water runoff carrying channels in this area so that flooding problem can be minimized up to the extent possible. The sensitivity of SWMM parameters is studied on the resulting runoff. The results show that, with small variation in properties of sub-catchments like imperviousness, flow width, Manning's coefficients for overland flow, depression storage, and slope, the runoff and its properties are greatly affected. CN is found to be the most sensitive parameter, and depression storage in pervious area is the least sensitive parameter.