Expanding systems of mountain roads in developing countries have significantly increased the risk of landslides and sedimentation, and have created vulnerabilities for residents and aquatic resources. We measured landslide erosion along seven road segments in steep terrain in the upper Salween River basin, Yunnan, China and estimated sediment delivery to channels. Landslide erosion rates along the roads ranged from 2780 to 48 235 Mg ha-1 yr-1, the upper end of this range being the highest rate ever reported along mountain roads. The two roads with the highest landslide erosion (FG1 Combining double low line 12 966 Mg ha-1 yr-1; DXD Combining double low line 48 235 Mg ha-1 yr-1) had some of the highest sediment delivery rates to channels (about 80 and 86%, respectively). Overall, 3 times more landslides occurred along cut slopes compared to fill slopes, but fill slope failures had a combined mass > 1.3 times that of cut slope failures. Many small landslides occurred along road cuts, but these were often trapped on the road surface. Given the magnitude of the landslide problem and the lack of attention to this issue, a more sustainable approach for mountain road development is outlined based on an analysis of landslide susceptibility and how thresholds for landslide trigger mechanisms would be modified by road location and different construction techniques.
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