Geotechnical study of urban soil and subsoil 148 of fez city (N. morocco) and natural risk Mapping using geographic information system (gis)

Abstract

Over the past four decades like all imperial cities of Morocco, the urban area of Fez City (Rif, Northern Morocco) has continued to grow and develop locally on dangerous grounds consisting of soft impervious clayey and marly substrate which are subject to multiple constraints and issues. These issues are made worse by rapid population growth coupled with serious administrative delays in the development and planning of Fez City. All these circumstances have generated an unstable building situation highlighted unfortunately by some tragic events. Indeed, as the statistics show, the majority of large buildings disorders may be due to incompatibility of foundation soils with the type of construction. Furthermore other types of less noticeable disorders, which represent major costs to the Moroccan society, are related to variation in the geometry of the soil such us volumetric changes of clay soils (shrink-swell phenomenon) or landslides events on the steepest slopes. These soil factors are affecting all infrastructures (e.g., buildings, roads and structures). The present research aims to identify and characterize all urban and suburban soils and lithology in the Fez City, using geotechnical and hydrogeological studies, field investigations, and exploitation of geological, hydrological and topographic data available in the area. All the required information has been sorted, analyzed and re-organized within a digital data base. Map layers and data cross-referenced with management plans using the Geographic Information System (GIS) were used to map instability risk areas according an increasing degree of hazard. Three categories of natural risk areas have been therefore identified: High risk areas (HRA); Medium risk areas (MRA); Low risk areas (LRA).