Over the last fifty years, increasing human activity in contact with rivers has contributed to the progress of the alluvial forest in the floodplains of Western Europe (Piégeay, 1995; Peiry, 1997; Vautier, 2000). Along the Allier River, an overall lowering of the channel due to gravel extraction, coupled with changes in agricultural practices and the absence of large floods, allowed forests to develop on alluvial banks that had previously been swept regularly by floods (Malavoi, 1998). As alluvial forest spreads, it modifies flow conditions. For the same flow value as in the past, the floodplain water level increases, resulting in a higher flood risk that administrators must manage. In order to provide administrators with the necessary knowledge for sustainable management of the Allier River floodplains, a vegetation and channel dynamics study was conducted on a segment of the Allier in the Val d'Allier nature reserve. The length of the segment is roughly 7.5 km, and can be divided in two distinct zones: 1) the alluvial upstream part, where the riverbed is very unstable laterally and develops wide meanders that may move as much as 20-30 meters per year and 2) the downstream part where, due to the presence of Holocene terraces and the emergence of the substratum released by the alluvial extractions, channel mobility is much more reduced. The study on fluvial geomorphologic changes and the increasing vegetation cover was based on 8 series of aerial photographs taken between 1946 and 2000. The study was conducted on two levels. First, we studied river landscape change over the whole segment, using a Geographical Information System coupled with statistical analysis of landscape structure. This study revealed a constant progression of the wooded vegetation accompanied by a reduction in fragmentation and a complex plant mosaic. Then we divided the study sector into 500-meter-long sections, using multivariate statistical procedures to analyse the data. The aim was to show the evolution of trajectories for the various sections between 1946 and 2000, to compare their transformation logic, and to date breakdown phases with the landscape dynamics.