Effects of different types of vegetation recovery on runoff and soil erosion on a Wenchuan earthquake-triggered landslide, China

Abstract

Abstract:In order to find suitable vegetation types for wider earthquake-triggered landslide rehabilitation in the eastern Longmenshan, we chose six vegetation types, which included three artificial restoration vegetation types (shrub Paeonia decomposita, deciduous tree Betula albo-sinensis, and evergreen tree Cryptomeria fortunei), two natural restoration vegetation types (middle and high coverage of grasses), and one residual vegetation. Soil quality, runoff, and soil loss were evaluated for the six vegetation types. We found that high coverage of grass prevented surface runoff and soil erosion more effectively than other vegetation types, and the deciduous tree and shrub were more suitable for soil quality recovery than the evergreen tree after the landslide. Among the three artificially planted vegetation types, the roots of the deciduous tree had stronger expansion ability than those of the shrub and evergreen tree. Our results indicated that high coverage of grass and deciduous trees could complement each other to achieve a good restoring effect, which would not only help reduce surface runoff and soil erosion but also facilitate the formation of fertile islands and enhance the stability of subsurface soils. Therefore, the two vegetation types could be used to form an effective vegetation restoration pattern for wider earthquake-triggered landslide rehabilitation in this region.Key words: earthquake-triggered landslide-fertile island-runoff-soil erosion-soil quality-vegetation type On May 12, 2008, a catastrophic earthquake with a magnitude of Mw 8 and a focal depth of 19 km (11 mi) occurred at the Wenchuan area of the Longmenshan fault in Sichuan Province, China. The earthquake caused a colossal fault rupture with a distance of approximately 270 km (168 mi) and triggered enormous landslides; it was the worst mountain disaster in the 20th and 21st centuries (Chigira et al. 2010). After the earthquake, investigations were conducted using Beijing No. 1 and IKONOS earth observation satellite images with ground resolution of 32 m (105 ft) and 1 m (3 ft), respectively (Di 2008). The total area of landslides induced by this earthquake was 2,260 km 2 (873 mi 2 ), which was far larger than that of recent earthquakes in mountainous areas, such as the Chi-Chi earthquake in 1999 that occurred in central Taiwan (Lin et al. 2006), the Mid-Niigata Prefecture earthquake in 2004 that occurred in northwest Japan (Chigira and Yagi 2005), and the Kashmir earthquake in 2005 that occurred in northern Pakistan (Sato et al. 2007).The earthquake-triggered landslides changed green vegetation into naked rock and bare soil. The absence of a thick soil layer discouraged the percolation of rainfall, facilitated flow over the slopes as runoff, and increased the possibility of severe soil erosion when intense prolonged rainfall occurred. A preliminary estimation of soil erosion in landslides resulting from the earthquake was about 55.86 × 10 8 t (61.58 × 10 8 tn) (Chen et al. 2009). In order to reduce soil erosion and protect the enviro...

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