Preparation of flood hazard potential map using two methods: Frequency Ratio and Statistical Index (Case study: Aji Chai Basin)

Floods are considered one of the most important and abundant geomorphic hazards in the country, which cause a lot of damage every year. Aji Chai basin, located in East Azerbaijan province, witnesses devastating floods every year due to its large area and special topographical conditions. Therefore, the main aim of this study is to prepare a flood hazard potential map in this basin. To achieve this aim, 18 parameters effective in the occurrence of this hazard and two statistical methods of frequency ratio (FR) and statistical index (SI) have been used. The investigated parameters were Elevation, Slope, Aspect, Rainfall, Distance to the river, River density, Normalized Difference Vegetation Index, land use, Distance to bridge, Distance to dam, lithology, hydrological soil groups, Topographic wetness index, Sediment transport index, Stream power index, Drainage texture, Geomorphology and earth curvature. The location of the past flood points in the area was used to determine the parameters weight and implement the research models. The final maps were prepared from the product of the weights of each parameter class in their information layers and were classified into five classes using the Natural Breaks tool. Study the final maps showed that hazard zones spatial distribution patterns were similar in both models. In this way, the areas downstream of the basin and around the main streams of the area are the most dangerous zones. The accuracy evaluation of the results of both models with the ROC curve showed that the values of the area under the curve for SI and FR models were 0.945 and 0.919, respectively, which shows the excellent performance of both models in preparing flood hazard maps.