Physical Characterisation of River Corridors from Orthophotos: Challenging Issues and First Application to the Rhone Hydrographic Network

According to the Water Framework Directive (WFD), "good ecological status" of all aquatic environments should be achieved by 2015. To validate this objective, we set up management tools to assess the physical condition of rivers. To avoid field work, which is a long and tedious work, and in order to achieve homogeneous data throughout the network, we created geomatic tools based on an object-oriented approach. We made a series of tests on the basin of the Rhône River (France) to assess the feasibility of extracting information from high resolution photographs so as to set up indicators of riverscape and aquatic habitat patterns. We present two examples of applications, one based on a sample of reaches within the catchment for typological purpose and one based on a single reach to highlight its longitudinal structure. The first example concerns the characterisation of braided rivers. The sites assessed are distributed throughout the Rhône basin (France). The second example concerns the study of fish habitat along the Drôme River (a tributary of the Rhône River). * Corresponding author.