Assessment and mapping of areas at risk of flooding using a combined AHP and GIS multi-criteria analysis model ‒ case study of Sidi Aissa city (Algeria)

Floods are among the most hazardous natural disasters, which pose significant threats to human lifeat both global and national scales due to severe human, material, and environmental losses. The increasing frequency of floods, compared to other natural hazards, highlights the urgent need of their evaluation and the mitigation of their impacts. This study aimed to assess and map flood-prone areas in the city of Sidi Aissa, Algeria, using the analytical hierarchy process (AHP) and geographic information systems (GIS). The city was chosen because of the three rivers running through it. A model combining a multi-criteria statistical approach and GIS was employed. The study focused on analyzing the factors influencing flood occurrence, including land use, elevation, slope, drainage density, distance from river and roads, topographic wetness index (T.W.I), and normalized difference vegetation index (N.D.V.I), To calculate the weights of these factors in the GIS environment, the AHP method was applied, resulting in maps specific to each criterion. The results revealed that land use (21.7%) and distance from river (18.2%) are the most critical factors influencing flood susceptibility and damage to nearby buildings. The study shaped a flood susceptibility map divided into three categories: areas with very low flood susceptibility, accounting for 29% of the total area; areas with moderate flood susceptibility, accounting for 40% and areas highly susceptible to flooding, making up 31%. Furthermore, the study demonstrated the effectiveness of using AHP and GIS in simulating potential floods and identifying flood-prone areas, thereby highlighting their importance in planning and mitigating flood risks in the future.