Mapping of Flood Risk Areas and Prevention Measures: A Case Study of Foum Elkhanga Watershed

Abstract

Introduction: Floods are major natural disasters resulting from multiple environmental and anthropogenic factors. They cause considerable damage, affecting not only soil and agricultural production, but also infrastructure, material goods and, above all, the safety of local populations. South eastern Algeria, specifically the town of Sedrata, which encompasses the Foum Elkhanga watershed, is among the areas most vulnerable to this recurring phenomenon.

Objectives: The objective of this study is to produce a map of the potential flood risk in oued foum elkhanga watershed, using the MCDA-AHP model, as well as to validate the reliability of the results obtained.

Methods: Flood susceptibility mapping can be carried out using several approaches. However, one of the most effective methods is based on multi-criteria analysis (MCDA) combined with the analytical hierarchy process (AHP). In this context, the AHP method was used to assign a relative weight to each conditioning factor. These factors were then combined using an overlay weighting technique in geographical information systems (GIS).

Results: The results show that flood susceptibility can be classified into four levels Low risk, Moderate risk, High risk, and very High risk. In general, the majority of areas classified as high risk are located in the city of Sedrata, close to the Fum Elkhanga dam, while areas classified as low, moderate and very high risk are mainly located in mountainous areas. Validation of the model, carried out by comparing the map produced with flood events recorded between 2002 and 2024, reveals an area under the ROC curve average of 78.3%, indicating a high level of accuracy and confirming the validity of the susceptibility map obtained.

Conclusions: The analysis also highlights the relevance of the conditioning factors used. Nine variables proved to be decisive in the modelling: TWI, Elevation, Slope, Rainfall, LULC, NDVI, Distance from River, drainage density, and Soil type.