Evaluation du recul du trait de cote sur une portion du littoral atlantique marocain de Mohammedia--Assessment of coastal retreat on a portion of the Moroccan Atlantic coastline at Mohammedia

International audienceLe littoral de Mohammedia, sur la côte atlantique du Maroc, est caractérisé par une forte urbanisation. Il présente une morphologie très variée avec une alternance de côtes rocheuses et de côtes sableuses. L'étude de photographies aériennes ainsi que l'analyse des profils topographiques de plages levés au cours d'un cycle annuel ont permis d'évaluer le recul que connaît cette portion du littoral atlantique marocain, du fait des contraintes naturelles et anthropiques The Atlantic coastline of Morocco at Mohammedia is characterised by heavy urbanization. It shows very variable morphology with alternating rocky and sandy beaches. The study of aerial photographs and the analysis of topographic profiles of beaches surveyed during an annual cycle have allowed the assessment of the retreat happening in this portion of the Moroccan Atlantic coastline, as well as natural and anthropic constraint

Heavy metals assessment in Oum Er Rbia bassin using WD-XRF and ICP-AES

International audienceThe analysis of water, suspended particulate matter (SPM) and sediment collected from Oum er Rbia Moroccan basin for the content of six elements has been performed utilizing ICP-AES and WD-XRF methods. Sediment have been analyzed by WD-XRF; Water and MPS by ICP-AES. The detection limits are sufficient for most of the elements to be determined. Results were assessed for the accuracy by the analysis of a multi-elemental standards. The results for most of the elements obtained were accurate to about 2-15%. The objective of the analysis were to determine the geochemical areas on this bassin, to explain the mechanisms of sediment transport and nevertheless, to assess the pollution of the bassin by heavy metals generated by human activities. This work interests only the last aspect. It has done one 30 samples of water and SPM, and about 80 sediments. Samples were collected along the river, between its source in meddle Atlas and the Atlantic ocean at Azemour city. The results obtained on the basin were normalized to the international norms

Analyse multi-élémentaire par fluorescence X à dispersion d'énergie des apports fluviatiles et des sédiments superficiels de la plate-forme atlantique du Maroc

L'analyse multi-élémentaire d'une trentaine de sédiments d'oueds et de l'océan atlantique du Maroc a été réalisée en utilisant des spectromètres X à dispersion d'énergie et des sources radioactives d'excitation en Fer-55, Cd-109 et Am-241. Les échantillons ont été collectés de la plate-forme continentale atlantique, de Tanger à Agadir et des oueds situés entre ces deux villes. Les objectifs de cette analyse sont : * la caractérisation géochimique des sédiments en vue de l'approche du transfert de matière du continent vers l'océan en tenant compte des données morphologiques, climatiques et géologiques de l'environnement sédimentaire. Les échantillons ont été prélevés par benne de la plate-forme continentale atlantique et des lits des oueds suivants, du Nord vers le Sud : Tahaddart, Loukkos, Sebou, Bou Regreg, Oum er Rbia, Tensift et Souss. Les régions du Nord dont la plupart sont irriguées présentent un climat humide alors que celles du Sud ont un climat semi-aride à aride avec des oueds intermittents. * la détermination de pollutions possibles de la zone littorale en relation avec l'activité anthropique, principalement au large des zones urbanisées. la précision des résultats a été évaluée par l'analyse de deux matériaux standards de référence de 1'AIEA (Agence International de 1'Energie Atomique), le sédiment «SL-1» et le sol «soil-7». Cette précision est de 5% pour la plupart des éléments majeurs alors qu'elle n'est que de 10 à 20% pour les éléments traces.The XRF analysis of about 30 sediments from Moroccan oueds (rivers) and atlantic continental shelf for the content of major and trace elements has been performed, utilizing the energy dispersive X-ray spectrometer and radio-isotope excitation with Fe-55, Cd-109 and Am-241 annular sources. Samples have been collected from Moroccan atlantic continental shelf from Tanger to Agadir and oueds between these cities. The objectives of this analysis were : * to determine the geochemical areas on Moroccan atlantic continent, * to explain the mechanisms of sediment transport from the continent to the sea throw the oueds using morphological, climate and hiterland impacts. Thus, sample have been collected from atlantic continental shelf and the following oueds, from the north with a humid climate and irrigated areas to the south with a semi-arid to arid climate : Tahaddart, Loukkos, Sebou, Bou Regreg, Oum er Rbia, Tensift and Souss, * to assess the eventual pollution of the coast by human activities, mainly at regions which are very urbanized. Results were assessed for the accuracy by the analysis of standard reference materials from IAEA (International Atomic Energy Agency), soil-7 and SL-1 sediment. The results obtained for most of the major elements were accurate to about 5% while the accuracy of trace element determination was much worse, 10 to 20%

Spatial correlation between the predictor variables and the weighting values calculated during the mapping of the environmental factors of mass movements in the Beni Idder region (northern Rif)

The Tleta of Beni Ider region located in the SW of Tetouan (Rif Septentrional) knows many mass instabilities. The diagnostic via the inventory, the mapping and the characterization of mass movements was made by using satellite imagery, aerial photography and field data coupled with existing documents (geological, geomorphological,…). The understanding of both their spatial distribution and the mechanism generating them, is very complex because of the existence of an important number of natural factors (geological, geomorphological, hydrological) in a relative mountainous landscape with deep valleys, steep slopes and significant elevation changes. Thus, a multidisciplinary approach was adopted to elaborate the landslide susceptibility map of the region taking into account interactions and causal relationships between the various natural parameters that tend to accentuate and aggravate the setting of landslides. The multidisciplinary database allowed us to evaluate the susceptibility thanks to a bivariate probabiliste model (Weight of Evidence). The obtained landslide susceptibility map is a major contribution to the development of urban development plans in the region

Spatial correlation between the predictor variables and the weighting values calculated during the mapping of the environmental factors of mass movements in the Beni Idder region (northern Rif)

The Tleta of Beni Ider region located in the SW of Tetouan (Rif Septentrional) knows many mass instabilities. The diagnostic via the inventory, the mapping and the characterization of mass movements was made by using satellite imagery, aerial photography and field data coupled with existing documents (geological, geomorphological,…). The understanding of both their spatial distribution and the mechanism generating them, is very complex because of the existence of an important number of natural factors (geological, geomorphological, hydrological) in a relative mountainous landscape with deep valleys, steep slopes and significant elevation changes. Thus, a multidisciplinary approach was adopted to elaborate the landslide susceptibility map of the region taking into account interactions and causal relationships between the various natural parameters that tend to accentuate and aggravate the setting of landslides. The multidisciplinary database allowed us to evaluate the susceptibility thanks to a bivariate probabiliste model (Weight of Evidence). The obtained landslide susceptibility map is a major contribution to the development of urban development plans in the region