Flood Inundation Mapping for Porsuk Stream, Eskişehir, Turkey

Flood is one of the most widespread and catastrophic natural hazards for settlements in different parts of the world. Eskişehir has faced numerous floods at varying scales, especially in the last century. Porsuk Stream moves in an artificial channel through the Eskişehir city center. The bed of Porsuk Stream is expanded and cascaded at the entrance to the city center, and the stream has been turned into one of the attractions of the city by increasing its water level with nine regulators. Expanding the river bed is a frequently used method to reduce flood risk. However, in Eskisehir, the fact that the river bed is kept largely filled with water is a major source of risk in case of flooding. The study is based on a scenario in which flooding occurs due to the failure of regulator covers to open. In the study field, the sensitivity of the numerical field model that was created along the stream bed was further improved by measuring lengths and depths throughout the channel. Within the framework of the scenario, the water levels that can change with flood discharges were determined, and inundation areas were calculated. The results revealed that, according to the flood discharges in Porsuk Stream with probabilities of occurrence in every 50, 100, and 200 years, areas of 3.20 km2, 4.03 km2, and 4.48 km2 would be flooded, respectively. The maximum discharge with a return period of 200 years (Q200) is 194.46 m3/s, which, if realized, would result in inundation of 1.58 km2 of residential areas and 0.55 km2 of agricultural land. Of the total flood area, 35% will be residential areas, 33% will be airports, 12% will be agricultural lands, 9% will be green areas, 7% will be industrial areas and 3% will be sports facilities.