HR: 15:30h
AN: H43A-07    [Abstracts]
TI: Epic Erosion Along Newly Constructed Roads in Yunnan, China
AU: * Sidle, R C
EM: sidle@slope.dpri.kyoto-u.ac.jp
AF: Geohazards Division, DPRI, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
AU: Kono, Y
EM: kono@cseas.kyoto-u.ac.jp
AF: Kyoto University, Center for Southeast Asian Studies, Kyoto, 606-8501, Japan
AU: Yamaguchi, T
EM: kono@cseas.kyoto-u.ac.jp
AF: Kyoto University, Center for Southeast Asian Studies, Kyoto, 606-8501, Japan
AB: The recent expansion and construction of new mountain roads in northwestern Yunnan Province, China, poses problems related to landslides and surface erosion that are impacting the headwaters of three great river systems: the Salween, Mekong, and Yangtze. Many of these newer roads are simply blasted into unstable hillsides with virtually no attention paid to optimal road location, construction practices, and erosion control measures. During summer 2006, seven people traveling in a minivan along a newly constructed road to Weixi were killed by a landslide. A survey conducted along a this 23.5 km road section (4 yr old) in the headwaters of the Mekong River revealed epic levels of landslides and surface erosion. Based on a preliminary survey, the road erosion was categorized as moderately severe, severe, or very severe, and a representative 0.75 to 0.90 km stretch of road was then surveyed for both landslide (based on dimensional analysis) and surface erosion (based on soil pedestal height). Average mass wasting rates (9608 t ha^-1yr^-1) along the road were more than 13 times higher than surface erosion (720 t ha^-1yr^-1), even though surface erosion rates are among the highest reported for disturbed lands. Dry ravel constituted a minor proportion of the mass wasting: 4% in the severe erosion section of the road and 0.5-0.6% in the moderately severe and very severe sections. For the very severe erosion road section (6 km long), estimated landslide erosion alone was > 33,000 t ha^{- 1}yr^-1, 620 times the average landslide erosion from forest roads built in unstable terrain in western North America. These levels of landslide erosion along the Weixi road are the highest ever documented and are somewhat representative of erosion along new mountain roads in this region of Yunnan. Sediment produced from roads is highly connected to fluvial systems; we estimate that 80-95% of the direct sediment contributions into the headwaters of these rivers are attributable to road erosion and landslides. These epic sediment loads represent cumulative effects that may persist in these important transnational rivers for decades.
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1839 Hydrologic scaling
DE: 1860 Streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2007 Joint Assembly