Morphological evolution of the Middle Loire River (France): Definition of geomorphic homogeneous river reaches

International audienceSince the12thcentury, the Loire River (France) has been intensively modified by the construction of flood embankments, navigation structures and the exploitation of sediments in the main channel. Those anthropogenic actions have considerably accelerated the incision of the riverbed. In 1995, granular extractions in the main channel stopped; a different morphodynamic behaviour of the Loire is suspected, which may have astrong impact on some infrastructures such as nuclear power plants and bridges located along the river.The purpose of this study is to better understand the morphological evolution of the ‘‘Middle Loire’’ River, which represents a linear section of about 450 km. Herein we present the definition of homogeneous reaches used to characterize the morphological evolution since the 1950s. For each reach defined evolution in plan, in length and cross sectionnal data are analyzed. The Middle Loire has been partitioned into 174 reaches with an average length of 2.5 km. Albeit the general trend observed over the last 50 years is a narrowing of the channel active width and an incision of the river bed, the morphological evolution of some reaches appears to decelerate since granular extractions stopped in 1995