Abstract
Abstract. 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 = 12 966 Mg ha−1 yr−1; DXD = 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.
Highlights
There is ample evidence of the effects of mountain road development on landslide initiation, only recently has this issue been raised within the context of sustainable development and the potential collapse of certain ecosystem functions (Sidle and Ziegler, 2012; Sidle et al, 2013)
The highest rate of landslide erosion (48 235 Mg ha−1 yr−1) occurred along the 1-year old road leading to a future hydropower plant just south of Daxingdi (DXD, Fig. 2)
The erosion rates measured along these seven unpaved mountain road segments (2780 to 48 238 Mg ha−1 yr−1) are higher than the range documented (1410 to 33 450 Mg ha−1 yr−1) along the newly constructed paved road near Weixi, Yunnan, indicating that such epic levels of landslide erosion and sedimentation are potentially widespread throughout the northern Yunnan region
Summary
There is ample evidence of the effects of mountain road development on landslide initiation, only recently has this issue been raised within the context of sustainable development and the potential collapse of certain ecosystem functions (Sidle and Ziegler, 2012; Sidle et al, 2013). The extent of environmental damage caused by landslides along mountain roads in developing nations is poorly understood. Sidle et al.: Epic landslide erosion from mountain roads in Yunnan, China supported by organizations such as the Asian Development Bank, the Food and Agricultural Organization of the United Nations, and the World Bank, largely based on perceived socioeconomic benefits (van de Walle, 2002; Balisacan, 2005; Hettige, 2006). Long-term sustainability assessments that weigh the relative benefits and impacts of rural mountain roads, including socioeconomic tradeoffs, have not been conducted (Sidle et al, 2013)
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