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Accueil du site → Doctorat → Canada → Modélisation spatiale de l’érosion hydrique dans un bassin versant du rif marocain : validation de l’approche géomatique par la sédimentologie, les traceurs radio-actifs et la susceptibilité magnétique des sédiments.

Université de Sherbrooke (1995)

Modélisation spatiale de l’érosion hydrique dans un bassin versant du rif marocain : validation de l’approche géomatique par la sédimentologie, les traceurs radio-actifs et la susceptibilité magnétique des sédiments.

Ait Fora, Abderrahman

Titre : Modélisation spatiale de l’érosion hydrique dans un bassin versant du rif marocain : validation de l’approche géomatique par la sédimentologie, les traceurs radio-actifs et la susceptibilité magnétique des sédiments.

Auteur : Ait Fora, Abderrahman

Université de soutenance : Université de Sherbrooke,

Grade : Doctor of Philosophy (Ph.D.) 1995.

Résumé
Erosion is a component of the geological cycle which perpetually shapes the landscapes covering the globe. Human activity, whether through agricultural activities, urban area development or the search for new energy sources often provokes irreversible modifications to the environment, which tends to accelerate erosion and eventually the degradation of the natural environment. Erosion imposes considerable costs to the Moroccan economy, by reducing the fertility of agricultural lands, and by silting hydraulic infrastructures which in turn reduce the life span of retaining dams. The objectives of this study carried out in the Tleta watershed (North of Morocco) are : (1) to quantify the amount of sediments produced by water erosion in the basin and transported to the retaining dam. (2) To determine the most susceptible areas to erosion. (3) to propose infrastructures on the light of the results derived. The proposed methodology uses new technologies such as remote sensing, geographical information systems, the use of radioactive tracers and the magnetic susceptibility of sediment. The quantification of erosion is based on the integration of the factors related to erosion, following the modified Wischmeier model (MUSLE) which are : (1) the soil erodibility factor (K) determined from the Wischmeier nomograph, (2) the topographical factor (LS) generated by the digital elevation model (DEM), (3) the agricultural practices and evolution factor (C) derived from remote sensing, (4) the rainfall and runoff effect (Rm) calculated from hydrological modelling (hydrolpl model) using the Soil Conservation Service method. The results of the quantification (in t/ha/year) for the three years retained for this study are 19, 62 and 46 respectively for 1975-1976, 1976-1977 and 1990-1991. Mean silting for a 10 year period is 44 t/ha/year. This result is very close to that of the year 1990-1991 during which average rainfall was recorded. Qualification provided by the activity of Cesium-137, by sampling units representative of the watershed, produced a spatially average total erosion 45 t/ha/year. The magnetic susceptibility of sediments permits to differentiate two areas in the watershed, an area which contributes to silting and an area which produces sediments which do not reach the retaining dam. Land management calls upon soil conservation and anti-erosive measures by applying biological and mechanical methods. Interventions must be first concentrated in the BV2 sub-basin as well as the entire eastern portion of the Tleta basin.

Présentation (Amicus)

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