These habitats with the accumulation of gravel, sand or silt are typical of wandering or braided river systems. They develop on rivers with significant variation in discharge and are maintained by torrents that regularly disturb or rearrange river banks and bring new sediments. They occur in mountainous areas from glacial river floodplains in the alpine belt to broad floodplains in the piedmonts and from boreal to Mediterranean Europe. The erosion–accumulation processes and fluctuating water level, including periods of submersion, cause spatio-temporal heterogeneity resulting in a mosaic of different successional stages ranging from very sparse pioneer vegetation to more closed stands of forbs and graminoids with scattered shrubs.