The primary objective of this research is to ascertain the potential flood risk in the Endek Stream Basin, which extends roughly north-south in the Horasan district of Erzurum, and its tributary, the Kırmızı Stream Basin, utilizing unit hydrographs. The study employed ArcGIS Pro software to determine the basin's hydrological characteristics and estimate the discharge volume at the basin outlet. Initially, a 25-meter resolution Digital Elevation Model (DEM) of the basin was procured. Using this model and hydrological tools, flow direction, flow accumulation, and slope maps of the streams within the basin were generated. These primary datasets facilitated the development of a spatially variable velocity field independent of discharge.
In the subsequent phase, a flow time map was created, delineating the duration required for water to travel from any point in the basin to its outlet. During the preparation of this map, 30-minute intervals were deemed significant for flood occurrence, and accordingly, the basins were divided into isochrone regions. Utilizing data derived from these analyses, unit hydrograph curves were employed to determine the discharge variation at the basin outlet following a potential sudden precipitation event. These curves were produced separately for both the Endek Stream Basin and the Kırmızı Stream Basin.
According to the analysis results, in the Endek Stream Basin, the discharge reached its peak approximately 18.5 hours after the onset of precipitation, with a discharge volume of 14,408.3 m³/s. In the Kırmızı Stream Basin, the peak occurred approximately 2.5 hours after the precipitation began, with a discharge volume of 4,251.3 m³/s. To assess the model's accuracy, reports of the July 2010 flood disaster in Saçlık Village, which resulted in six fatalities, were examined. These examinations revealed that the model yielded highly consistent results in terms of timing and magnitude.
Thus, it has been observed that such a study is beneficial in predicting the potential effects of flood disasters, particularly in terms of discharge magnitude and flow duration, and how the disaster might impact the study area. Consequently, it is anticipated that this research will assist authorities in formulating disaster management strategies.
However, more accurate and detailed results require the use of higher resolution data and advanced modeling techniques.

Keywords

Flood Hazard, Unit Hydrograph, Geographic Information Systems (GIS), Horasan, Erzurum.