Riparian vegetation responds to hydrogeomorphic disturbances and environmental changes and also controls these changes. Here, we propose that the control of sediment erosion and deposition by riparian vegetation is a key geomorphological and ecological (i.e. biogeomorphic) function within fl uvial corridors. In a 3 year study, we investigated the correlations between riparian vegetation and hydrogeomorphic dynamics along a transverse gradient from the main channel to the fl oodplain of the River Tech, France. Sediment erosion and deposition rates varied signifi cantly along the transverse gradient as a function of the vegetation biovolume intercepting water fl ow. These effects, combined with the extremely strong mechanical resistance of pioneer woody structures and strong resilience of pioneer labile herbaceous communities, Populus nigra and Salix spp., explain the propensity of biogeomorphic succession (i.e. the synergy between vegetation succession and landform construction) to progress between destructive fl oods. This geomorphological function newly identifi ed as an 'ecosystem function' per se encompasses the coupling of habitat and landform creation, maintenance and change with fundamental ecosystem structural changes in space and in time. Three different biogeomorphic functions, all related to the concept of ecosystem engineering, were identifi ed: (i) the function of pioneer herbaceous communities to retain fi ne sediment and diaspores in the exposed zones of the active tract near the water resource, facilitating recruitment of further herbaceous and Salicacea species; (ii) the function of woody vegetation to drive the construction of forested islands and fl oodplains; and (iii) the function of stabilised riparian forests to act as 'diversity reservoirs' which can support regeneration after destructive fl oods. Overall, this study based on empirical data points to the fundamental importance of sediment fl ow control by pioneer riparian vegetation in defi ning fl uvial ecosystem and landform organisation in time and in space.