Landslides distribution at tributaries with different evolution stages in Jiangjia Gully, southwestern China

Abstract. Jiangjia Gully (JJG) is known for its high frequency and variety of debris flows, especially the intermittent surges of various flow regimes and materials. Observation indicates that the surges come from various tributaries with different landslides activities. In this study, 81 tributaries of JJG are taken from DEM with 10 m grid cells, and the hypsometric curves are used to characterize their evolution stages; five stages are identified by the evolution index (EI, the integral of the hypsometric curves) and most tributaries are in relative youth stage with EI between 0.5 and 0.6. Then 908 landslides are interpreted from Quickbird satellite image of 0.61 m resolution, and it is found that LD (LD = landslides number in a tributary/the tributary area) increases exponentially with EI, while LA_p (LA_p = landslides area in a tributary/the tributary area) fluctuates with EI, meaning that landslides are inclined to occur in tributaries with EI between 0.5 and 0.6, and thus these tributaries are the main material sources supplying for debris flows.