10. Categorization of Urban Basin According to the Runoff Depth: Case Study of Katsushika Ward and Edogawa City Basin, Japan

Climate change has a tenacious impact on a large portion of the earth. As a result of that, many urban areas have experienced unrivalled scale of flooding. This research targets classifying an urban basin according to the depth of runoff. In order to estimate the runoff depth, a digital elevation model (DEM) has been delineated using ArcMap to identify the basins, sub-basins, flow direction, and streamlines. Furthermore, the delineated layers were essential to generate a hydrodynamic model via HEC-RAS of the studied area. Accordingly, the exported spatial data together with the precipitation values were utilized to develop a 2D-unsteady flow calculation of the adopted watershed. Consequentially, the runoff depth has been calculated and classified into 10 categories. The results concluded that nearly two-thirds of the study area has been saturated by the estimated runoff. In addition, less than a tenth of the basin has endured more than 500 mm of runoff depth. However, approximately a quarter of the region has experienced nearly 165 mm of the runoff. Eventually, this categorization will significantly help the decision makers to intensify protective measures on the most accumulating points of runoff in the studied watershed.