Physio-Géo ()
Soixante années de recherches en coopération sur l'érosion hydrique et la lutte antiérosive au Maghreb
Abstract
During the last 60 years, the topics treated by the researchers concerned with the soil and water conservation methods have changed.From 1945 to 1970, developers observed the importance of erosion damages: decrease of soil productivity, gullies, landslides, silting of dams and floods. Few researches were conducted on "soil and water conservation" (SWC), but many applications are made of mechanical (terraces, earth banks, sills) and biological techniques (complete protection and reforestation above the dams) used in the USA and in France. Geographers spatialised the traces of erosion processes and the erosion risks in case of rural development (J.M. AVENARD). From 1965 to 1985, studies concerned mostly the erosion quantification. In Tunisia, Y. Cormary and J.M. MASSON have assessed the factors implicated in the USLE model of WISCHMEIER with an original rainfall simulator. C. Floret, R. PONTANIER, J.P. DELHOUME and M. DELHUMEAU have studied on runoff plots and small watersheds erosion processes in arid, semi-arid and subhumid climates. In Morocco, the team of B. HEUSCH demonstrated on runoff plots and catchments 1/ that sheet erosion is less important than gullies and rivers erosion, 2/ that the length and gradient of slopes are less important than the position in the landscapes and 3/ that exceptional rainstorms induced most of erosion damages by saturation of the topsoil than usual rains. In Algeria, A. DEMMAK found that the wadis solid transport is related mainly to the extension in the watersheds of argillite, marl and shale outcrops.Since 1985, a research team of INRF and IRD realised, in Algeria, investigations on SWC techniques efficiency, developed intensive agro-ecosystems valorising better the ground and labour, restored gullies with various sills models and various plants and trees valorising the badlands: they called the system "GCES". In Morocco, teams of ENFI foresters, Rabat University geographers and IRD have described and analysed 30 SWC systems developed by farmers living in the Atlas mountains. IRD with the Faculty of Marrakech developed a methodology using teledetection, rainfall infiltrometer on 1 m2, surface status and GIS in order to spatialise erosion risks and types of SWC managements necessary in a mountainous watershed of 270 km2.
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