STATISTICAL-MODELS OF THE HYDRAULIC HABIT AT - TOOLS FOR ECOLOGY

Quantitative estimates of the ecological impacts of river management r equire a description of the hydraulic local habitat. Statistical hydra ulic models aim at providing estimates of the frequency distribution o f local hydraulic variables in a stream reach, as a function of averag e characteristics of the reach. Such models bridge the gap between the working scale of fluvial hydraulics (the reach scale), and the needs of ecologists (local scale). Because they use simple input variables, they offer large possibilities of application, in particular for instr eam flow assessments. Statistical models reflect general trends common to complex fluvial systems and therefore contribute to explain the ro le played by the physical characteristics of the habitat.