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<p>Sediment (dis)connectivity plays a critical role in influencing the geomorphic processes and sediment delivery in debris flow areas. Similarly, changes in geomorphic constraints have a significant impact on sediment connectivity. Therefore, understanding the potential effects of geomorphic indicators on sediment connectivity can identify geomorphic adjustment hotspots and help to inform geo-geomorphic hazard prevention and control. To explore the effects of geomorphic restrictions on sediment connectivity, we applied an index of connectivity (IC) and the digital terrain analysis (DTA) in Jiangjiagou Gully, Yunnan Province, SW China, which is famous for its high annual occurrence of debris flow events. And according to the natural topography conditions, the watershed was separated into three sections from up to down. The IC and 13 geomorphic indicators are calculated for each cell of the watershed’s 5 m resolution digital elevation model (DEM). GeoDetector was used to investigate the geomorphic indicators and their interactions affecting the spatial distribution of sediment connectivity. The results showed that the IC and geomorphic indicators have significant spatial heterogeneity in different regions. The IC value varied from -20.74 to 1.42 and the high-value areas overlap with the river network. LS factor, Topographic Characterization Index (TCI), and Terrain Roughness (TR) are the three factors with the greatest impact on IC value for all regions. In addition, the interactions significantly enhanced the explanatory power of single indicators. Particularly, Topographic Wetness Index (TWI), while single explanatory power is extremely low, its interactions display higher influences than others. Therefore, carrying out low-cost geomorphic adjustments based on the key geomorphic indicators can reduce or block sediment connectivity, further achieving the aim of water and soil conservation and geo-geomorphic hazard control. This study contributes to improving our understanding of the geomorphic processes and provides a scientific basis for nature-based solutions in typical debris flow small watersheds.</p>

Medium‐sized catchments exhibit different patterns of sediment yield than small catchments and large river basins (taking scale dependency into account) and play in soil loss from upstream areas with downstream sediment transportation over larger spatial scales than small catchments. Few studies have used reservoir depositional records to assess historical sediment yields at the scale of a medium‐sized catchment. By analyzing six cores obtained from reservoir deposits, this investigation reconstructed the recent sediment yield from a medium‐sized agricultural catchment (the Xujiaya catchment in Northern China) and examined the changing pattern of sediment yield over the past 57 years. The cores were dated using the 137Cs and 210Pbex methods. The historical specific sediment yields (SSYs) were estimated based on the original reservoir capacity curve and the depositional chronology modeled using a composite chronological model based on the constant rate of supply (CRS) approach (i.e., the C‐CRS model). The mean SSYs estimated from the six cores over each of seven short stages (i.e., 1959–1963, 1964–1972, 1973–1980, 1981–1989, 1990–1997, 1998–2007, and 2008–2016) defined over the 57‐year study period ranged between 4.6 ± 1.8 and 16.2 ± 6.3 t ha−1 yr−1, with a mean value of 8.1 ± 3.2 ha−1 yr−1 for all seven stages, and this mean value can be used to broadly represent the sediment yield from the catchment since dam construction. These SSY values are relatively high, reflecting intense agricultural disturbance and the underlying lithology. The values were highest for the 1959–1963 stage and lowest in the following stage of 1964–1972 and then generally increased over the successive stages of 1973–1980, 1981–1989, and 1990–1997 before decreasing slightly during the last two stages after 1997. This change was driven mainly by human activity over the past 57 years. The results indicate that the environmental factors (e.g., human activity and lithology) influencing sediment yield in a medium‐sized catchment are more complicated than those affecting a small catchment and reveal the characteristic pattern of sediment yield in medium‐sized catchments.