Evaluation of a Reliable Method for Flash Flood Hazard Mapping in Arid Regions: A Case Study of the Gulf of Suez, Egypt

Flash floods are severe disasters that devastate the environment, society, and economy in arid regions. Due to the scarcity of observed data from prior incidents, flash flood hazard mapping (FFHM) using Remote Sensing (RS), Geographic Information System (GIS) and hydrological modeling elements has recently become a feasible method for the fundamental management of basins. El-Shamy approach is a straightforward, widely used method for FFHM. This is the first study to investigate the effect of a stream threshold (St) change on the results of El-Shamy approach. Furthermore, runoff peak discharge- and runoff volume-based flash flood hazard degrees (Rp-HD and Rv-HD) were explored. For El-Shamy approach, St = 0.1 km(2) was found to be the best among the considered values for well-distributed estimates of flash flooding potential. A Receiver Operating Characteristic (ROC) curve using historical data was employed to evaluate the considered methods and revealed that El-Shamy suffered from a precision lack, with an Area Under Curve (AUC) equal to 0.36 and 0.45 for low and high hazard basins, respectively, indicating a slight reverse prediction tendency. While Rp-HD and Rv-HD attained a similarly significant and reliable accuracy, with an AUC equal to 1.0 and around 0.865 for low and high hazard basins, respectively. Moreover, Rp-HD was recommended due to its cautious prediction. Accordingly, the FFHM for the study area was presented and associated guiding sustainable management measures were suggested to help decision-makers partially achieve Sustainable Development Goals (SDGs).

Automated summary

Flash floods cause severe damage to the environment, society, and economy in arid regions. This study examines the impact of stream threshold changes on the results of the El-Shamy approach for flash flood hazard mapping (FFHM) and explores runoff peak discharge- and runoff volume-based hazard degrees. The results show that a stream threshold of 0.1 km(2) provides the most accurate estimates of flash flooding potential using the El-Shamy approach. However, the El-Shamy approach has a lack of precision, whereas the Rp-HD and Rv-HD methods exhibit reliable accuracy. The FFHM for the study area is presented, along with suggested sustainable management measures.