Hydraulic and Hydro logical Urban Catchment Modeling: (Case Study: Shashemene Town

In 2016( G C), most of the states of Ethiopia are suffered from a disastrous flood that caused extensive damage to homes, agricultural lands, commercial property, and public infrastructures. Shashemene town and its surrounding were among the affected area by the storm runoff. Good example was Shashemene-Aje -Arbaminch road that was cut by the landslide combined with high flooding from the upstream of the Shashemene city catchment area in June 2016(GC). Modeling of such Storm water has a major role in preventing of flash floods and urban water-quality problems issues. However, in-detail modeling of large urban areas is time-consuming as it typically involves model calibration based on highly detailed input data. Storm water models of a lowered spatial resolution would thus appear valuable if only their ability to provide realistic results could be proved. This study proposes a methodology for rapid catchment delineation and stormwater management model (SWMM) parameterization in urban area. A catchment delineation and SWMM parameterization is conducted for an urban area, in the Shashemene city. GIS methodology is utilized for simultaneous processing of data representing large areas. Literature values are also of importance where no spatial data is available. To evaluate the parameterization results, the SWMM application is run using an hourly data series of meteorological observations covering a period of ten years. The routines established in the study make the catchment delineation and subdivision process reasonably fast and accurate, although manual work cannot be fully avoided due to defects in the input data. In contrast, the SWMM parameterization of the low-resolution subcatchments is the more challenging part and involves larger uncertainties. Even so, the model application provides sufficient results compared to literature and other studies and measurements performed on the site. Overall, the methods developed in this study provide a feasible approach for SWMM parameterization in large urban areas with visible difference of actual drainage capacity of storm water runoff and determined canal capacity from existing drainage facilities in the city of Shashemene .This require additional canal to alleviate this drainage problems