Ruisseaux, têtes de bassin et risques : l’exemple des plateaux limousins (France)


L. Touchart, N. Lheritier


Abstract.- Brooks, headwaters and risks: the example of the highlands in Limousin (France), Risks in headwaters are not only the same as those in great rivers (floods, very low waters, pollution, eutrophication, etc.). Headwaters present specific hazards as blockages in brooks and very small artificial waterbodies on springs. The authors study geomorphologic and thermal risks of headwaters in a metamorphic and plutonic landscape of forested and grassy highlands, with thousands of ponds. Methods used micro current meter, sieving, Rubin’s grilles and recording thermometers. Main results are about biological habitats. The risk of clogging on spawning areas concerns fine sands (less than 0.8 mm). The density of habitats is higher in brooks than in rivers. Many natural blockages and some artificial dams prevent fishes of running up, but they allow alevins to run down. If the brooks are damaged, the fish population will decline on the main streams.  The thermal risk in brooks depends on weirs, spillways and sluices of ponds.


            Key words: risks, geomorphologic  thermal eutrophication, Limousin