This paper describes initiation and development of specific alluvial channel forms, connected with the supply of coarse-grained hillslope sediment. The study was carried out in gravel-bed rivers, located in mid-mountain areas (the Sudetes and the Carpathian Mountains) in Central Europe. In the river channels studied, where input of hillslope material is abundant, patterns of sedimentation and erosion are determined by hillslope processes. Two types of primary sediment source in mountain temperate rivers, with flat valley floors, were identified: mass movements, in particular landslides, and supply of angular coarse-grained slope material to streams from cut-bank sections. The introduced coarsest hillslope sediment is only entrained during floods which destabilize the river systems downstream of the supply points. At these river channel sections, development of new, and transformation of existing, alluvial channel forms is observed. Sediment accretion and progradation of bars downstream of the hillslope sediment delivery zones (HSD zones) is connected with: activity of these zones (frequency of hillslope sediment supply), size of coarse-grained, angular deposits introduced into the river channels and frequency of flood events. The largest depositional forms, such as gravel-rich debris longitudinal bars, lateral bars with a rock block core and lateral bars downstream of an HSD zone, comprise coarse, usually gravel-sized sediment. The main feature of their initiation and progradation is deposition of large rock blocks within or at a short distance downstream of the supply points. Lateral sediment accretion of the bars leads to river channel constriction during subsequent floods and development of other alluvial channel forms such as transverse gravel-rich debris ribs, diffuse gravel-rich debris sheets, side debris bars and small sandy-rich gravel separation bars. These forms create depositional complexes which are observed in the river channel within the zone of the hillslope sediment supply and for a few hundred meters downstream.