Flood Hazard Zonation Using Spatial Hydrologic Analysis in GIS and Interpretation of Satellite Images: A Case Study on Aharchay Catchment

Recognizing the flood hazard zones and its spatial analysis is an effective step in preventing financial and human losses from this natural disaster, and as a result, it contributes to the sustainability of the environment. In the current research, the flood risk assessment in the Aharchai catchment area located in East Azarbaijan province is presented.

In this regard, geographic information system and spatial analysis are used, and in order to create flexibility in the integration of existing information, fuzzy logic is used for flood risk zoning. SCS method was also used to estimate runoff height and peak discharge.

Flood risk zoning using fuzzy logic shows that about 10% of Ahrchai catchment area is in high and very high-risk classes. Based on this, the floodplains and flat surfaces of the foothills for reasons such as low relative height, low slope, proximity to the main waterways, intersection of branches and high drainage density, high values ​​of valley depth and low values ​​of land surface convexity are more vulnerable to floods. The findings show the high spatial variation of runoff height and peak discharge at the level of Ahrchai sub-basins.

With the help of the proposed method, the determining factors in the occurrence of floods and also the potential areas of runoff were determined. In general, the southern sub-basins of Ahrchai catchment have the potential to produce runoff and low peak flows. On the contrary, a significant part of the northern sub-basins of the study basin has high runoff and peak flow production potential. The northern half of the Ahrchai basin corresponds to the southern slopes of the Qara Dagh mountain range, whose geological structure is mainly composed of igneous rocks with low permeability. In this way, the sub-basins in the northern half of the basin have a high potential for producing runoff due to receiving more rainfall and low permeability of the soil.