The hydrographic networks can provide geomorphosites of high quality such as gorges, river corridors with shifting channels or braided pattern. To identify them, we developed tools for characterising biophysical features of the valley bottoms. We developed geomatic tools in order to avoid fieldwork, which is a long and tedious work and to achieve homogeneous data throughout a network covering an entire region or a country. Two approaches have been tested. On the one hand, GIS layers and DEM were used to describe the geometry of the alluvial plains and to target gorges reaches. On the other hand, we coupled orthophotos provided by IGN (National Geographical Institute) to vectorial layers to understand the fluvial patterns and to identify reaches of high environmental values, such as braided reaches. We did a series of tests on the River Drôme (France) to assess the feasibility of extracting information from high-resolution photographs so as to set up indicators for the physical characterisation of hydrographic networks. The data thus obtained was used to identify, characterise and locate the valley and fluvial corridor patterns, including reaches of quality corresponding to the so-called "geomorphosites".
