HYDRO 2015 INTERNATIONAL IIT Roorkee, India, 17-19 December, 2015 20 th International Conference on Hydraulics, Water Resources and River Engineering 1 Review of urban stormwater models Vinay Ashok Rangari* 1 , Ajey Kumar Patel 2 , N V Umamahesh 3 1 Research Scholar, National Institute of Technology, Warangal 506004, India 2 Assistant Professor, National Institute of Technology, Warangal 506004, India 3 Professor, National Institute of Technology, Warangal 506004, India (Water & Environment Division, National Institute of Technology, Warangal 506004, India) Email: vinayrangari@gmail.com Telephone/Mobile No.: +91 9970536805 Abstract Increasing trend of urban flooding is a universal phenomenon and poses a great challenge to urban planners the world over. Proper management of stormwater drainage may be a solution to urban flooding problems but suitable selection of model for a particular watershed is a challenge. This paper reviews models for simulating stormwater quantity in an urban environment. A number of models have been developed by academic institutes, government organizations and some private agencies. Most of these models are based on conventional methods for runoff generation and routing. Some models add groundwater/baseflow component and several include infiltration component. In this paper few well known flood simulating models in current use are examined and compared in terms of their functionality and accessibility and features of all these stormwater models have been summarized. The models chosen represent a wide range of capabilities, spatial and temporal resolutions. Primarily the models are grouped as urban models which are specifically designed to simulate urban stormwater quantity and quality and non-urban models which are capable of being adapted for use in urban stormwater problems. These models are classified according to the type of modeling, availability of additional features and accessibility. This review can be helpful for the researchers and stormwater managers for choosing a model according appropriate parameter requirements of a specific urban watershed. Keywords: Stormwater, Watershed, Urban flood, Model. 1. Introduction Increasing trend of urban flooding is a universal phenomenon and poses a great challenge to urban planners the world over. The un-even distribution of rainfall coupled with urbanization, filling up natural drainage channels and urban lakes and their encroachment for the use of high-value urban land are the causes of urban flooding. Urban flooding is significantly different from rural flooding and so also are the strategies to deal with them. Urbanization leads to developed catchments which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times (NDM Guidelines, 2010). Consequently, flooding occurs very quickly due to faster flow times, sometimes in a matter of minutes. Although volume of water to be handled is not as severe as a flash flood of a river system the property damages and indirect financial losses are significant as this flooding occurs in highly populated areas. Accurate modelling of extreme urban flood events requires a better understanding of overland flow paths and the capability of representing the re-entry of surface flows into the below ground drainage network. But due to the complexity of both the underground and above ground systems within urban areas, up to now there has not been an easy way to represent both systems interactively (Andres et al., 2007). Models capable of simulating stormwater quality and quantity appeared in the earlier 1970s and were developed primarily by US government agencies, such as the USEPA (Zoppou, 2001; Mitchell, 2001). Since then, a number of urban watershed models have been developed. Most of these models are 1D models and are based on principle of mass, energy and momentum conservation. Some models are event based models and other are continuous simulation type. These urban drainage models are able to simulate the drainage system correctly until there is no overflow from the network inlet or manhole. When such overflows occur due to insufficient drainage capacity of downstream pipes or