La susceptibilité aux mouvements de terrain dans la province de Chefchaouen : Analyse spatiale, modélisation probabiliste multi-échelle et impacts sur l'aménagement & l'urbanisme

Abstract

Geological hazards represent a research topic that is in constant development. Populated areas are ever expanding and the requirements for the control of the hazards they represent are becoming increasingly significant. Orogenic zones are among the areas affected by different types of hazards. This study focuses on the evaluation of mass movement (MM) hazard which is the most common hazard in the Northwest part of the Rifain belt in Morocco. It introduces a three-step procedure to assess mass movement hazard (MMH). Nine contextual variables that characterize the geological environment (lithology, fracturing, seismicity, slope gradient, elevation, aspect, stream‟s net, precipitation and land-use) were mapped and classified in order to better understand their interrelationships and their respective effects in the onest of MM. Following this, the classification, inventory, description and the analysis of the MM were carried out by interpretation of high remote sensing data associated to the field study. Finally, MMS was assessed using a multi-scale approach (small = 1/100,000 ; mean = 1/50,000). At the small scale, this assessment was carried out using an index-based approach where the rating and weighting of each parameter was introduced based on real statistical data to reduce the subjectivity of the method. At the meso-scale, this evaluation was performed by applying and comparing two probabilistic approaches. These are: (i) the bivariate weights of evidence approach (WOEA), and (ii) the multivariate logistic regression approach (LRA). WOEA proved most successful in predicting landslides hazard and LR proved most successful in modeling rockfalls and debris flow at the meso-scale in a North African mountain environment. The various maps produced constitute a powerful decision-making tool to present, compare and discuss scenarios of town and land-use planning, i.e. urban planning, works or road plans. These results are part of a sustainable development framework which allows mitigating the socioeconomic impacts that are usually noticed during the release of MM.