| dc.description.abstract | Soil depth is an important factor in the physical based method of the prediction of shallow landslides. It is also critical in the estimation of the shallow landslide volume. This reaserch selected the Shihmen Reservoir catchment area as a study area to develop empirical fomulas for estimation of soil depth on natural slope. By using field obvervation and hand auger, I performed the investigation of soil depth at several test sites. The measurement spots were selected on natural slope, which are formed by soil production and
modified by mild slope processes, avoiding falts, river banks, river terraces, collapeses, gullies, and artificial slopes. Accompany the depth measurement, coordinate as well as slope gradient and aspect at the spot were also measured
and recorded. Terrain curvature, wetness indexe and lithology at a spot are then reduced from DTM and gelogical map, and put together for use. Regression analysis of soil depth and controlling factors is performed in order to build an empirical estimation model of soil depth at Shihmen Reservoir catchment. Different combinations of factors and form were testd in the study, and R2 value, residual analysis and root mean square of error were used to evaluate the appropriateness of an empirical estimate model. Result reveals that the best estimate is the mutiple regression using slope gradinet, terrain curveture, wetness indexe, slope aspect, and lithology as factors; the R2 value is 0.91, the residual value of 75 data (90% of all data) are within ±0.2m, the standard deviation of residual is 0.137m, and the root mean square of error is 0.14m. A simple formula using only slope gradient is also recommended; the R2 value is 0.82, the residual value of 56 data (67% of all data) are within ±0.2m, the standard deviation of residual is 0.218m, and the root mean square of error is 0.22m. | en_US |