Flood Management in the Eighth District of Herat City using Low Impact Development and Their Evaluation with EPA-SWMM Model

One of the main problems in urban development is the increase of impenetrable levels, which leads to an increase in runoff and the occurrence of urban floods. In this study, the current situation of floods in the eighth district of Herat city was investigated using the EPA-SWMM mathematical model  in terms of flooding. Then, six different modes were modeled separately and simultaneously in the form of two methods low-impact development of rainwater storage barrels (in two different sizes) and biological biomass units. The results of this study showed that by using low-impact development methods, the negative effects of floods with a return period of 10 years can be reduced by at least 40%. After that, simulation has been done using the flood mitigation reservoir method. The results showed that the construction of delayed reservoirs causes a delay in the peak discharge time and reduces the peak flood discharge. Also, the use of flood mitigation reservoir and unit biomass method and rain barrel method with larger diameter reduces flooding by 80% and the use of unit biomass method and the smaller diameter barrel method reduces the volume of urban floods by 75%.