Mapping Flash Flood Potential and Risk Level Using GIS Techniques and the Flash Flood Potential Index (FFPI) in Amman Zarqa Basin of Jordan

Jordan is located in an arid and semi-arid climatic zone, where about 80% of the country, known as the "Badia". Generally, this is classified as a dry or arid region. Climate change is expected to exacerbate the current aridity and scarcity of water resources in Jordan. Sudden and extreme weather events are becoming more common; this likely means longer and drier summers, more severe droughts, harsher winters, and an increase in flash floods. Jordanian Civil Defense reported that during 1963-2019, 451 people were killed and about one million people affected by flash floods. This research aims to determine the critical locations of flash floods in the Amman Zarqa Basin. This research methodology depends on using four variables (slope, vegetation cover/density, soil type/texture, and land use/cover) under the GIS environment to calculate the Flash Flood Potential Index (FFPI). This index has not been used in Jordan (up to our knowledge). Five scenarios were used in this study, based on previous reviews and the last one (scenario 5) based on Jordanian experts of flash floods in Jordan. The results show that increasing the weight of slope and land use in different FFPI equations will increase the values of FFPI. Reducing the vegetation density by 50% resulted in limited effects on the importance of FFPI. The risk level is divided into four categories (extreme, high, medium, and low) related to the FFPI values. Scenario two, which uses equal weights for all parameters, had the lowest risk level all over the area. Scenario four, which double the consequences of the slope and the land use with respect to the other two parameters. This has the highest risk level over the study area. Based on equation no. 5, which is modified based on Jordanian experts' opinion, the low-risk level covered 9.01% of the basin. Besides, the medium, high, and extreme risk levels covered 72.96%, 15.89%, and 2.14% of the study area, respectively.