The use of SWMM model in determining the ability to collect and extract runoff in Babolsar , Mazandaran Province

Urban watersheds due to their development, have more complex hydrological behavior than natural watersheds, and understanding their hydrological response will help to design appropriate flood control facilities. In this study, SWMM model was used to investigate the potential of urban runoff production in a part of Babolsar urban area. The purpose of this study was to analyze the water availability of rainwater collected during different return periods for urban use. For this purpose, the SWMM model defined 65.65 ha of study area in the form of six hydrological units (from 5.94 to 16.82 ha), six output nodes and four channels were defined, and the height of runoff from 24-hour rainfall was obtained with different return periods. According to these results, the 24-hour rainfall with a 25-year return period is 70.37 mm, of which 33.73 mm for infiltration and 35.60 mm for runoff. Results showed that about 52.1% of rainfall of Babolsar City plan could have the ability to become runoff. The highest runoff coefficient is in the hydrological unit S3, which has a value of 0.637 at the 100 year return period. However, the lowest runoff coefficient is in hydrological unit S1 which has a value of 0.352 at 2-year return period. The results also showed that the runoff coefficient is directly related to the return period and the larger rainfall has a higher runoff coefficient. Through the collection systems, in addition to reducing the flood hazards of Babolsar City, a water supplement that offsets part of household consumption in the non-urban sector, also water resources management can be done.