Use of a total station to monitor post-failure sediment yields in landslide sites of the Shihmen reservoir watershed, Taiwan

Abstract

Landslides have both immediate and extended-duration effects on sediment discharge. Examining the role of post-failure soil loss/sediment yield of landslides is essential for basin management purposes. The comprehensive measurement of sediment production of existing landslides could provide a better understanding in this aspect. This study investigated the post-failure sediment yield of 13 landslide sites in the Shihmen reservoir watershed, Taiwan, during the rainy seasons of 2006 and 2007 using a total station. Our study showed that soil loss is mainly controlled by rainfall conditions, and the geometric and geographic characteristics of each landslide can significantly influence the efficiency of sediment delivery. We also observed that rainfall is important in determining landslide retrogression/enlargement, although vegetation in the landslide area increases with time. We obtained a large amount of landslide measurement data, which could be useful for future landslide modeling.

We suggest two regression models for estimating gross soil loss using cumulative rainfall. The estimated gross soil loss values of 0.78 to 1.06 m yr− 1 are equivalent to 18,096 to 24,592 t ha− 1 yr− 1. Using these estimates, we assessed the sources of sediment in the watershed, and found that the ratio of landslide erosion, soil loss after landsliding, and soil erosion from other parts of the watershed was approximately 66:31:3. This study implies that remedying existing landslides is more effective than any other solution in reducing sediment production in the watershed.