Divergent responses of hillslope-gully systems controlled by check dams to rainstorm events in the Loess Plateau, China.

Hydrological forcings and erosion dynamics are influenced by natural factors and anthropogenic activities. Flooding events associated with climate change are attributed to heightened rainfall intensity and frequency, alterations in landscape patterns across various scales, and an elevated risk of flooding and water scarcity. This study combined landscape pattern indices with sediment connectivity to analyze changes in sediment connectivity during extreme rainfall events in various check dam-controlled hillslope-gully systems. Aerial and field surveys of four systems within the Caijiachuan watershed, conducted before and after the rainstorm event in October 2021, utilized unmanned aerial vehicles (UAVs) and remote sensing imagery. Landscape indices were applied to analyze the spatial pattern characteristics preceding and following the rainstorm event. The sediment connectivity index (IC) assessed sediment transport connections in the chosen systems. It was found that extreme precipitation led to increased landscape fragmentation, decreased biodiversity, and higher sediment connectivity, especially on steep slopes compared to gully channels. Soil erosion hotspots were found on slopes between 0-50°, with landslides occurring in areas of high sediment connectivity. This altered the landscape pattern and further boosted sediment connectivity. Various hillslope-gully systems reacted differently to rainstorms. This study highlights the value of using sediment connectivity to assess check dams' responses to extreme precipitation, improve watershed and land management strategies, and evaluate soil erosion control measures in fragile ecosystems.