Modeling flood spreading-hazard-risk maps of Sakarya Kaynarca basin: Seyren stream

The flow rate, and the water level depending on the flow rate changes in streams. In periods of high flow, the streams can overflow the stream bed. As a result of floods, economic, ecological and environmental damages and even loss of life can occur. In order to prevent the damage caused by floods and to keep the damage in minimum, it is necessary to carry out flood risk analysis studies with the help of hydrological data. For this purpose, it was deemed necessary to carry out hydraulic analysis of the Seyren stream, located in the district center, by means of package programs, and to determine the flood spreading areas, flood hazard and flood risk maps after the big flood event that occurred in the district of Kaynarca in Sakarya province on 30.09.2018. Flood recurrence rates of 5, 10, 50, 100 and 500 years were calculated by using precipitation data with deterministic and statistical methods. Flood levels on 30.09.2018 and the detected flood flow rate were used for calibration. Flood propagation maps were prepared by using the hydraulic analysis package programs with the calibrated model. Flood hazard maps were created based on depth and velocity parameters. Risk coefficients have been mapped by using population, building usage pattern and material damage factors that may occur as a result of flood. Flood risk maps were created in GIS environment by using risk coefficients and flood hazard maps. With the help of these maps obtained, residential areas under danger and under risk, the amount of population and the damages that may occur in case of possible flood were determined and recommendations were made to prevent these damages.