Dynamic impact of hillslope landslide sediment transfer to ecological environment recovery in earthquake disturbed area

Abstract

In the Wenchuan seismic disturbed region, the landslide sediment transfer has seriously damaged the vegetation. On the contrary, the vegetation recovery can improve the post-seismic slope instability by the root reinforcement effect and reduce landslide sediment transfer. However, due to limited earth observations, it remains elusive that the dynamic response of hillslope landslide sediment transfer to ecological environment recovery in earthquake disturbed area. We analyzed the prolonged evolution of landslide sediment transfer potential (LSTP) and surface recovery in epicentre of Wenchuan earthquake using the standardization landslide sediment transfer potential index (SIH) and normalized difference vegetation index (NDVI), respectively. As well, the dynamic relationship between landslide sediment transfer and vegetation recovery is discussed. We found that the LSTP in regions between Gengda and Caopo was dominated by high and extreme levels between 2008 and 2013, and it gradually enhanced during this period, which poses a negative impact on vegetation recovery. On the contrary, the LSTP continued to decline after 2013, which provided a positive impact on vegetation recovery, and average NDVI recovered at a rate of 0.05 yr⁻¹. In recent years, more than 78.33% of the study area was dominated by moderate and slight LSTP, and the NDVI has almost returned to pre-earthquake levels, which provides a linear impact on decay of landslide erosion and landslide sediment supply for channel. However, the species that breed slowly (trees) will gradually rehabilitate for a longer period, so the impact of vegetation restoration on landslide sediment reduction needs further long-term observation.