Geo-environmental risk in the upper valley of the Oued Sebou (Fès, Central Morocco): a preliminary approach
Introduction
In the main cities of most third world countries the yearly demographic growth is close to 6%, and this is also the case for Fès in Morocco, a city that has been declared a World Heritage Site by UNESCO. During the last decades many people of the neighbouring villages have migrated to the city of Fès for a better life standard.
The demographic growth and the consequent expansion of the urban areas is causing problems related to the organisation and the management of the main services (roads, water, electricity, sewage systems, etc.) but also from a geological and environmental point of view (Ministère de l’Intérieur, 1992).
The area of Fès has been the object of many geological (Charrière, 1984, Charrière, 1990, Essahlaoui et al., 2001), geomorphological (Laouina, 1973, Martin, 1981) and especially hydrogeological studies (Chapond, 1964, MacDonald & Partners, 1990, DRPE, 1995, Bahaj et al., 2001, Saddiki et al., 2001). The geo-environmental risk approach has been carried out many years ago (Chapond et al., 1967) and recently these researches have been started again using remoter sensing techniques (El Wartiti et al., 2001).
The project entitled “Geological resources and geo-environmental risk in the Oued Sebou basin. Implications with the coastal dynamics” financed by the Sardinian Region, has aimed to make a preliminary analysis of the geo-environment of an area of almost 1000 square km around Fès analysing LANDSAT TM5 satellite images, followed by two ground surveying campaigns. On the basis of these investigations the scope of the project was to define the different landscape units, selecting the areas of major hydrogeological and geo-environmental risk.
Section snippets
Geography and geology of the region
The city of Fès is situated in the eastern lowest part of the Saı¨ss plain, at an elevation of approximately 400 m a.s.l., in the northern part of Morocco, in an area bordered by the mountains of the Rift to the North and those of the Middle Atlas to the South. From a geological point of view the study area contains sedimentary rocks of different ages ranging from Triassic to Quaternary, overlying a Palaeozoic impermeable basement complex mainly composed of schists, quartzites and metalimestones
Methodological approach
The methodological approach applied in this research consists of the analysis of satellite imagery for the recognition of the homogeneous territorial units according to an integrated classifying system. The basic themes that allow one to obtain two thematic maps are the land cover and the roughness of the land surface that are traduced in forms and processes of landscape morphology.
The experiences of the authors with this type of analysis have demonstrated the validity of this methodology for
The geo-environmental risk
Geo-environmental risk is dependant on the intrinsic characteristics of the territory (lithology, acclivity, landcover, etc.) and on the climate. Meteorological data evidence that the area around Fès is characterised by a semi-arid climate with a dry season of 5–6 months and an average annual rainfall of less than 500 mm. In fact, in the two considered meteorological stations (Fès Saïss and Fès Direction Régionale de Hydrogéologie) the average annual rainfall is 504 mm (considering 30 years of
Conclusions
The major geo-environmental risks indicated by our studies and the analysis of earlier researches, are related to flooding, erosion of soil, landslides, rock fall, desertification, pollution of soil and of subsurface and subterranean water, and to land subsidence (Chapond et al., 1967, Laouina, 1973).
The most vulnerable areas to these types of hazard are:
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the slopes on Miocene and Pliocene marls, where impressive badlands can form and accelerated erosion takes place on the steepest surfaces;
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the
Acknowledgements
This study has been carried out with the financial aid of the Sardinian Regional Government in the framework of the Projects “Geological resources and environmental risk in the Oued Sebou. Implication with coastal dynamics” (Responsible; Prof. Carlo Marini) and “Study of Coastal areas with environmental hazard” (Responsible; Prof. Sandro De Muro) (Regional Law no 43/1990) and “Geological resources and environmental risk in the Oued Sebou. Implication with coastal dynamics” (Responsible; Prof.
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