Revision of Surface- Runoff Drainage System by Simulation and Application of Retention Basins)Case Study: East Eghbal Catchment, Mashhad)

Nowadays along with development of societies and border extension of cities, their impervious areas increase and therefore higher amount and volume of runoff accrue. Thus control of flood in urban areas has always been a major concern of designers and managers. In this research the performance of East Eghbal urban drainage system located in the south and southeast of Mashhad city was analyzed in a region with area of 71 Km2. To estimate the physical parameters of subcatchments and hydraulic parameters of conduits, and some other computations like calculation of weighted average, subdividion of catchments into sub-catchments and providing land use map, the GIS was used. Because of the complicacy in simulation of urban drainage system, MIKE SWMM was applied for rainfall - runoff simulation and hydraulic response evaluation of the urban drainage system. Finally, 3 suitable places were recognized for retention basins based on topographic maps, flood conduits position and land surveying. Results showed that 6 conduits had difficulty and computed flow was more than the designed flow. Urban drainage system was simulated again by the presence of retention basins and results showed that these basins could reduce the flood peak from 8 to 100% and also infiltrate 12.35 m3/h and also infiltrate of water.