1 and 2 dimensional flood analysis with HEC-RAS: Gumushane Bahceci̇k stream example

Factors such as rapidly increasing population, unplanned construction, improper land use and development of floodplains have caused the soil surface to become impermeable, which has seriously increased the number of floods and the damages they cause in recent years. This situation has made it an inevitable necessity to determine flood risks and take necessary precautions, especially in residential areas. The study area, Kelkit district of Gümüşhane province, was initially a safe area in terms of floods, thanks to the fact that the first settlements were built away from stream beds. However, due to the increasing population and unplanned urbanization in the last 100 years, the occupation of low terraces and stream beds and the acceleration of construction have led to an increase in the frequency of floods. For this reason, Kelkit has turned into a residential area where flood risks must be determined and necessary precautions must be planned. In this thesis study, flood risk maps of Bahçecik Stream passing through the village were prepared using geographical information systems (GIS) in order to identify areas with possible flood risk in Yeniyol Village settlement in Kelkit district of Gümüşhane province. Bahçecik Stream, passing through residential areas and agricultural lands, causes floods, especially in April and May. Within the scope of the study, the digital elevation map of the region was taken from the USGS website at 30m resolution and digitization operations were performed on the TIN map at 5m resolution with a module of ArcGIS software. In the light of the hydrometric data obtained from the DSI 22nd Regional Directorate, calculations were made according to the Q25, Q100 and Q500 flood recurrence flow rates in the HEC-RAS software. As a result of these calculations, water surface elevations and flood boundaries were determined. In this study, suggestions were presented for obtaining the most realistic results in GIS-based flood analysis and for predicting and eliminating the damages that floods will cause in residential areas and agricultural lands.