THE INFLUENCE OF RIPARIAN VEGETATION COVER ON DIFFUSE LATERAL SEDIMENT CONNECTIVITY AND BIOGEOMORPHIC PROCESSES IN A MEDIUM-SIZED AGRICULTURAL CATCHMENT, AUSTRIA

Connectivity concepts are often used to describe the linkages between sediment sources and sinks within a catchment. Vegetation plays an important role as it influences surface roughness and the local capacity to store sediments and water. However, knowledge about the effects of riparian vegetation on lateral sediment connectivity as well as on the processes and factors that govern them is rare and presents an important research gap. This paper assesses the influence of riparian vegetation cover type on diffuse lateral sediment connectivity on valley floors and investigates biogeomorphic processes acting in forested riparian zones of a medium-sized agricultural catchment. Governing processes and factors are assessed using GIS-based overland flow pathway modelling and geomorphic field surveys together with multivariate statistics (principal component analysis, logistic regression modelling). The results reveal that diffuse lateral sediment connectivity is highly influenced by the respective type of riparian vegetation cover. Forested riparian zones significantly reduce sediment inputs and act as strong disconnectors between the catchment area and the river channel. Topographical features called root dams emerge from biogeomorphic processes in forested riparian zones and act as buffers that limit the connectivity between landscape compartments.