Comparing Hydrology and Hydraulics Surface Routing Approaches in Modeling an Urban Catchment

Abstract

Urban hydrological environment is difficult to assess with its complex verity of components by using simple hydrological models which are not fully capable enough to represents the exact urban catchment’s features. The urban catchments comprising with various infrastructures having low permeability and low roughness coefficients have increased their runoff volume, while decreasing the time of concentration. This has been caused urban flooding threatening the urban environments in many aspects. This study uses two of numerical modeling approaches to represent the urban catchment, and assess the flood risk of an urban catchment; hydrological surface routing approach and hydraulic 2D surface routing approach. Both approaches were combined with 1D hydraulic stormwater drainage network. XPSWMM was used as the modeling tool. Comparison of results of two approaches shows that the both approaches are suitable to represent urban catchment’s hydrological behavior, but the results of hydrological surface routing are more close to observation data. When representing the flood inundation areas, it is better to use the hydraulic approach since it calculates the flood depth by using surface runoff and excess water from pipe network at the same time.