Assessment of Landslide Risks Through a Multi-Disciplinary Approach: A Case Study of Al Hoceima, Northern Morocco

Abstract

Landslides are very dangerous phenomena dependent upon several parameters and criteria widespread in Northern Morocco. Their management is complex because of the dangers posed to the population and by the habitat, but also due to the difficulty of remedial actions. To address this, a methodology is needed based on the analysis of land movements through a multidisciplinary approach combining geology, hydrogeochemistry, and geotechnics. This perspective was adopted in this study of landslides in the city of Al Hoceima (Northern Morocco), and in particular on the slope located in front of the Al Hoceima port, which shows a morphology of old landslides, and more recent ones subject to factors of instability or landslides that activate after periods of intense rain. The analysis and interpretation of satellite images reveals a complex morphology, shaped by a geology characterized by tectonic activity and often-altered lithology. From a geotechnical point of view, the latter induces low to medium mechanical characteristics. Inclinometric measurements situate the average depths of the sliding planes at between 15 m and 25 m. The chemical facies of the groundwater is sodium sulphate, sometimes tilting toward chloride-sodium, proof of a leaching of the autochthonous formations (Trias-Lias and Jurassic), to which is added the action of the rising water table. All these factors intervene directly in the destabilization of the slope. These results allow us to establish concrete actions for the stabilization of the slope.