CONSERVATION, LANDSCAPING AND RESTORATION OF WATERCOURSES WITH A NATURAL LOGIC

Different aspects of preservation, management and restoration of water courses are described with their concepts, methods, materials and resu lts. Special emphasis is given to bioengineering which may yield very good hydroecological results. Bioengineering is in keeping with a sust ainable development of hydrosystems used by man. It is based on the co nservation or, on the contrary, on the re-creation of dynamic riparian systems which are missing. Like other engineering sciences, it may so lve erosion problems with great technical efficacy, but with great eco logical efficiency. Living plants-are used as construction materials w hich are arranged in specific patterns and are not employed to decorat e civil engineering works. Intervention in a river is not always neces sary. A zero option is considered. The philosophy which governs interv entions in watercourses must be based on a natural logic (natural deve lopment) where the vegetable is privileged before the mineral : 1) Ass ess the need for interventions according to impacts and values to prot ect (zero option) - 2) Assess if bioengineering can solve the problems . - 3) If not, assess if mixed interventions are efficient. - 4) Only at this stage should a conventional civil work technique be applied if it proves reasonable and coherent. Regulating and landscaping a water course is not only a matter of hydraulic calculations. A knowledge of biological functions is needed to develop appropriate interventions. A fine analysis of the whole stream according to hydroecological criter ia has become essential. For successful conservation, natural interven tion and restauration of watercourses, guidelines are proposed.