Two-dimensional numerical modeling of flood wave propagation in an urban area due to Ürkmez dam-break, İzmir, Turkey

Abstract

This study investigated flood inundation in an urban area due to a possible failure of Urkmez Dam in Izmir, Turkey. The estimation of flood hydrograph upon partial failure of the dam and routing of the flood hydrograph along the narrow valley downstream were first performed by the one-dimensional hydraulic routing model HEC-RAS. The two-dimensional hydraulic routing model FLO-2D is then used to simulate the spreading of the dam-break flood after the flood wave exits the valley. Land use and land cover digital maps were utilized to find the spatially varying roughness coefficient for the floodplain. The influence of the buildings on the flood propagation was represented in the numerical model by the area reduction factor as well as the width reduction factor. The peak flow depth, peak flow velocity and time moment of the peak flow depth maps were shown in the GIS environment. The results reveal that flow depths can reach about 3 m in the residential area. In about 40 min after the dam-break, houses in the large section of the town would be under the maximum flow depths. The two-dimensional hydrodynamic model results were tested against experimental dam-break flow data of the distorted physical model of Urkmez Dam, which is consisted of the reservoir, dam body and downstream area including Urkmez Town. The model successfully simulated experimental flow depth data measured at different measurement locations.