Evaluation of the use of ponds in the surface runoff collection network by simulation method (Case Study: Mashhad East Eghbal Floodway)

Uncontrolled floods always cause extensive financial and human losses in cities. Flood control is one of the most important goals of urban management. In this regard, an attempt has been made to investigate the effect of delayed ponds on the flood control of the Eghbal Floodway located east of Mashhad. East Eghbal Floodway, with a sub-catchment of about 13850 ha, is one of the most significant floodways of the developing Mashhad metropolis, including eight major floodways and 213 sub-catchments with many urban facilities. To evaluate and simulate the flood path, the precipitation pattern was calculated using different methods, including the concentration time of each sub-catchment. The most extended length of the stream, the uniform distribution of catchment sensitivity, periodic block, and peak flood flow caused by critical rainfall with a 50-year return period were calculated at the outlet. Finally, according to the topography of the area and available places using two, three, and four detention ponds to consider 11 different scenarios (economic-hydraulic), the peak flow of the flood decreased, and the time of peak flow increased. By evaluating and comparing different scenarios, scenario number 11 (using four detention ponds reduces the peak flood discharge by 48%) was the best hydraulic scenario. In addition, scenario number 4 (using two detention ponds reduces peak discharge by 24%) was the best economic scenario. A dry trapezoidal catchment within the network with two outlets, a lower opening, and a rectangular overflow was modeled in SWMM5.0. Geographic Information System (GIS) and SWMM5.0 rainfall–runoff simulation have been used to determine the physical component of sub-catchments.