Sediment connectivity as a decision-support framework for sustainable management of ungauged catchments

Sediment connectivity provides a powerful conceptual and quantitative framework for understanding how water and sediment are transferred from hillslopes to channels and downstream receptors. Yet, its integration into practical watershed management remains limited, particularly in ungauged catchments where hydrological and sediment monitoring data are lacking. This study investigates how sediment connectivity can be utilized to identify critical sediment source–pathway–sink linkages that control the emergence of sediment-related management issues and indicate where management interventions are most effective for mitigating risk across diverse landscapes in the Czech Republic.

We analyzed sediment connectivity in three types of ungauged catchments representing key management contexts: (i) forested mountain headwaters affected by historical torrent control works, (ii) forested tributary catchments contributing sediment to the Dyje/Thaya River within the Podyjí/Thayatal National Park, and (iii) small agricultural catchments exposed to torrential rainfall and severe soil erosion. Across all sites, field-based mapping of sediment sources, buffers, and barriers was combined with GIS-based connectivity metrics, particularly the Index of Connectivity (IC) and the Effective Catchment Area (ECA). In agricultural catchments, these approaches were further integrated with process-based erosion modelling (WEPP and GeoWEPP) and validated using UAV-derived measurements of event-scale soil loss. The results indicate that management-relevant sediment dynamics emerge from the interaction of structural and functional connectivity rather than from static landscape properties alone. In forested headwaters, roads and torrent control structures act as barriers and buffers, reducing hillslope–channel and longitudinal connectivity. This allows critical sediment delivery zones and sediment-fed reaches to be identified. In protected, dam-fragmented catchments, the abundance of sediment sources and high structural connectivity do not result in effective sediment delivery, as large woody debris, small dams, and floodplain storage interrupt sediment transfer. In agricultural catchments, IC-derived flow paths closely match observed erosion patterns, and land-use scenarios demonstrate that the targeted placement of grass strips or low-erosion crops can substantially reduce sediment connectivity, erosion risk, and the downstream transfer of sediment during extreme rainfall events. Overall, the study shows that sediment connectivity offers a unifying and transferable framework for linking sediment sources, pathways, and impacts across diverse environments. When combined with field observations and erosion modelling, connectivity mapping supports the identification of critical reaches, disconnections, and hot spots and provides guidance for targeted, landscape-based mitigation of sediment-related issues in data-poor catchments.