الفهرس 
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Abstract
Flash floods are rapid hydrological responses that occur within a short timeframe (several hours to a few days). These events are characterized by an instant rise in water levels, reaching a maximum peak discharge in a short period. Flash floods are typically generated by intense rainfall and have the potential to cause a substantial damage on structural, social, and economic elements within the affected areas. Consequently, the generation of accurate inundation maps is important for differentiating between flood-prone and non-flood-prone regions.
Traditionally, hydrodynamic models have been employed to generate inundation maps. However, this approach necessitates a substantial volume of data, significant computational power, and considerable simulation time based on the complexity of the models and the value of the simulation time step. Recognizing these limitations, researchers have sought to develop effective, fast, and simplified models. One such model is the Geomorphic Flood Index (GFI), a valuable classifier used to generate flood extent maps through a simplified method that relies on available flood extent data for specific rainfall depths.
The primary objective of this study is to expand the utility of the GFI classifier to predict flood extents for uncalibrated rainfall depths. This advancement holds the potential to enable early warning systems for more accurate risk assessments, particularly during extreme events. Moreover, two additional objectives have been Included in the research: (1) improving the accuracy of simulated flood extent maps through the exploration of various calibration methods and (2) investigating the impact of various digital elevation models (DEM) with varying resolutions on the obtained inundation maps using GFA.
The study encompassed three case studies within arid regions of Saudi Arabia, each characterized by distinct topographies. High-resolution digital elevation models with a resolution of 1.0 meter and rainfall depths corresponding to return periods ranging from 5 to 100 years were utilized. To evaluate the accuracy of the predictions, the HEC-RAS 2D was employed to generate reference inundation maps. The results indicated a high degree of similarity between the obtained inundation maps using GFA and the reference maps by HEC-RAS, with accuracy levels exceeding 80%. Strong relationships between rainfall depths and the threshold GFI parameter were developed which allow the production of inundation maps for any rainfall event. This breakthrough promises to enhance flood risk management and early warning systems, particularly in regions vulnerable to flash floods.
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