owadays in most countries, urban development and imperviousness surfaces are increased. This cause the increase of volume and intensity of surface runoff in urban watershed. For control and management of these floods, the urban storm water drainage systems are required. In this study, geographic information system (GIS) is used for generation, storage and display the physical parameters, analysis of spatial data, hydrologic assessment and calculating the requirement parameters in rational method. With analyzing of spot height and using raster GIS, digital elevation model (DEM) of case study was determined with 2 meter of pixel dimensions. Flow direction and flow accumulation maps were determined for hydrologic assessment, identifying the main flow path and storm water collection template. Using of advanced GIS function, 4 catchments are delineated in case study. With generation of DEM, flow direction and flow accumulation maps for each catchments, concentration time map was determined and length of main channel, average slope and concentration time were calculated for using in rational method. With analyzing of land use map and using overlay GIS method, private green area and building themes were overlaid with land use map. Using statistical regression method, linear equations were produced for computing the impervious area, building area and open area for each land use. The results displayed that sport and business land uses had maximum impervious area percent and medical and historical land uses had minimum value. The residential land uses are 97 percent impervious that the minimum value was located in region 9 and maximum value in region 7. Business and tourist services land uses having the maximum building area percent. In average, buildings constitute the 58 percent of residential land uses area that region 6 with 64.1 percent and region 9 with 46.6 percent having the maximum and minimum value respectively. The six distribution functions including Normal, two parameter Lognormal, three parameter Lognormal, Pearson type III, Log Pearson type III and Gumbel were fitted to maximum rainfall intensity for durations of 15 to 360 minutes. The parameters of each distribution were computed by methods of moments and maximum likelihood. Then, based on least-square test, the Log Pearson type III distribution was selected for optimum distribution. Maximum rainfall intensity is computed for return periods of 2 to 200 years. Finally, Intensity- Duration- Frequency (IDF) curves and equations were determined. Using rational method, the storm water peak discharge was estimated for 4 catchments in case study. The database of these catchments is developed in a vector GIS system for better urban storm water management. The softwares were used in this study are Autocad 2005, Arcvieextensions including Spatia