Mapping of geomorphic dynamic parameters for analysis of landslide hazards:A case of Yangbi river basin on the upper Lancang-Mekong of China

Landslides are common hazards in orogenic belt areas.However,it is difficult to quantitatively express the driving effects of tectonic uplift and stream erosion on the occurrence of landslides on large spatial scales by conducting field investigations.In this study,we analyzed a relatively large region that extends over the Yangbi River basin on the upper Lancang-Mekong in China.A series of quantitative indices,including kernel density of the landslide(KDL),hypsometric integral(HI),steepness index(ksn),stream power(?),and stream power gradient(ω)were used to explore the promoting effects of tectonic uplift and stream action intensity on landslides by mapping geomorphic dynamic parameters combined with actual landslide data.The analysis showed that the HI value in the highest landslide risk area was approximately 0.47,and that the KDL in the region can be expressed as a function of steepness or stream power gradient of the channel network,namely,KDL=0.0127 Ln ksn-0.0167(R2=0.72,P<0.001)and KDL=0.0219 Lnω-0.0558(R2=0.21,P<0.02).Therefore,the lower reach of the Yangbi River basin,with higher steepness and stream power gradient,usually has a high uplifting rate and stream incision that drives landslides and causes the entire river network system to be in a stage of longterm active erosion.Furthermore,the results suggest that sediments were being rapidly discharged from the steep tributary channels to the mainstream.This practical situation highlights that the downstream area of the river basin is a high-risk area for landslide hazards,especially in association with heavy rainfall and earthquakes.