Unprecedented rates of landslide and surface erosion along a newly constructed road in Yunnan, China

Abstract

Field measurements conducted 4 years after the construction of a new portion of the Weixi-Shangri-La road in Yunnan, China, reveal that unprecedented rates of mass wasting occurred along the road with much of this sediment directly impacting the headwaters of the Mekong River. Landslide erosion (including dry ravel) exceeded 33,000 t ha -1 year -1 along the most severely eroded sections of the road and averaged more than 9,600 t ha -1 year -1 along the surveyed 23.5 km of road; these values are the highest ever reported for road-related landslides. While surface erosion was only about 7% of the total erosion from the road, it is still more than an order of magnitude higher than typical surface erosion rates from disturbed lands in Southeast Asia. Combined landslide and surface erosion from this road delivered an estimated 19 times more sediment to the river than the remaining 99.6% of the contributing catchment. These sediment inputs are aggrading local channels, promoting downstream sediment transport, degrading aquatic habitat, and creating the possibility for a future debris flood or hyperconcentrated flow.

Epic landslide erosion from mountain roads in Yunnan, China – challenges for sustainable development

“…In most cases, 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).…”

“…Although 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 et al, 2013). In particular, the extent of environmental damage caused by landslides along mountain roads in developing nations is poorly understood.…”

“…In particular, the extent of environmental damage caused by landslides along mountain roads in developing nations is poorly understood. While numerous international donors, non-governmental organizations (NGOs), and environmental advocates have attributed increased sedimentation in rivers and streams in these regions to shifting cultivation and deforestation (e.g., UNESCO, 1974;Eckholm, 1979;Volk et al, 1996;Marshall, 1999), more comprehensive investigations and analyses recognize that these land use practices exert much less influence on downstream sediment and aquatic resources than poorly constructed mountain roads (Sidle et al, , 2007(Sidle et al, , 2011Wasson et al, 2008;Ziegler et al, 2009). Of course, road and trail systems are associated with shifting cultivation and deforestation, but more recent, rapid expansion of road networks in mountainous terrain of developing nations have been linked to transitions from shifting cultivation to more intense agriculture, increased tourism, economic development, national defense, emergency evacuation routes, and hydropower development (Krongkaew, 2004;Nyaupane et al, 2006;Ziegler et al, 2012;Urban et al, 2013).…”

Broader perspective on ecosystem sustainability: Consequences for decision making

“…Oftentimes, >80% of the landslide and surface-eroded sediments directly reach stream and river systems (Fig. 3B) (76).…”

“…In the worst cases, mountain road construction is abandoned, leaving no access and a legacy of sedimentation problems. Examples of landslide-related deaths along these lightly traveled mountain routes have already been reported (76). Current development is paying little attention to road location or construction methods to control the mass wasting of rock and soil (40).…”