Flood analysis for Yozgat city center

Artificial ponds are built around city centers for water storage, irrigation, flood protection, renewable energy generation and social space. Due to the high population density in the city centers, the dense construction and the high impermeable surface areas, the sudden dam failure flood causes a high rate of loss of life and property. Within the scope of this study, in case of multiple failures of Kirazlı Pond, Çiftlik Dere Pond and Bekir Cevdet Dündar Pond located around Yozgat city center, a flood analysis was carried out for the city center. Pond level-volume curves were obtained with ArcGIS Geographic Information System (GIS) software using the Digital Elevation Model (DEM) with five meters resolution obtained from the General Directorate of Mapping (HGM). The 50 cm resolution DEM data, which forms the basis for the flood areas, was obtained from the General Directorate of Land Registry and Cadastre (TKGM). The surface roughness coefficient affecting the flood dispersal rate was determined by location using CORINE UA land use/cover city atlas data and orthophotos produced by HGM. The maximum base width, side slope and formation time of the breach that may occur in the Overtopping (OT) and piping (P) scenarios were estimated using the regression equations obtained from the dams that had previously collapsed. The outflow hydrographs formed as a result of the dam failures and the closed section of the Yozgat Stream passing through the city are modelled as one-dimensional (1D) in MIKE HYDRO River software. The spreading area of the flood resulting from the dam failure was modelled as two-dimensional (2D) in MIKE 21 FM software. 1D dam failure model and 2D flood propagation model were analysed together in MIKE FLOOD software. As a result of the analysis, the variation of the output hydrographs obtained from the 1D dam failure model, depending on the failure scenarios, was examined. 2D flood maps and hazard maps were created for the disaster that may occur in case of multiple dam failures. It has been determined that the closed stream sections and the culvert at the exit point are insufficient to meet the high flood flow caused by the dam failure. As a result of the flood, it has been determined that a certain part of the D200 Highway passing through the city and the underpass on the highway are below the flood level. Suggestions were made in order to reduce the possible flood effects in Yozgat city center.