A method for assessment of sediment supply and transport hazard and risk in headwater catchments for management purposes.

Headwater streams play an essential role in catchment hydrogeomorphology while supplying water and sediment to downstream reaches along the channel network. Adaptive management strategies which require ecological rehabilitation and natural hazards prevention methods are increasingly needed to sustain ecological services provided by headwater streams. However, environmentally sound and economically effective stream management techniques depend on relevant information on boundary conditions, operating processes and evolutionary trajectories of a river system, which are often unavailable. Therefore, it is desirable to provide river managers with scientifically rigorous, yet easy to apply tools (methods) to assess channel and catchment conditions. The present paper focuses specifically on the sediment supply and transport (SST) regime, a crucial component of the fluvial system and a source of significant hazard to people and infrastructures. The SST hazard and risk assessment procedure was developed for small headwater streams with a catchment area of up to ca. 50 km². The method comprises two core modules. Module 1 is designed to rapidly evaluate susceptibility to SST hazard based on four catchment variables (relief, lithology, erosion-prone surfaces, and connectivity). Module 1 is intended primarily for river managers to differentiate between catchments and identify those with the highest probability of SST hazard. Module 2 comprises a detailed evaluation of channel and catchment variables; thus, it is to be conducted applying basic training in fluvial geomorphology and GIS skills. Module 2 includes five successive steps: channel network segmentation, identification of segments with vulnerable and hazardous anthropic elements, determination of the dominant mode of sediment transport, determination of SST hazard category, and calculation of SST risk score. The method was designed to balance the present-day understanding of sediment flux in the catchment-scale sediment cascades and applicability for target end-users, mostly technically educated professionals and research scientists in river mechanics and erosion and sedimentation. [ABSTRACT FROM AUTHOR]