Citation

DeGraff JV, McKean J, Watanabe PE, McCaffrey WF. Transp. Res. Rec. 1984; 965: 32-37.

Copyright

(Copyright © 1984, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Stump Springs Road, a major timber-haul route in the central Sierra Nevada of California, suffered extensive landslide damage in the spring of 1982 and the spring of 1983. An estimated $1.3 million will be spent on major repair or reconstruction at sites widely distributed along a 23-km section. Geologic and geotechnical studies supporting remedial efforts yielded insight into the role of groundwater in these landslides. Landslide activity is a direct response to the nature of the precipitation event and infiltration capacity ande permeability of the materials present. During periods of infiltration, water percolates through coarse-grained, moderately permeable material until granitic bedrock is encountered. Groundwater then flows down gradient with the top of the saturated thickness roughly parallel to the bedrock surface. The importance of groundwater is seen in the dominance of flow-type movement. Calculated pore-pressure ratios typically reached 0.5 at the toe and 0.15 near the head. Observation wells at one landslide demonstrated that a failure surface coincided approximately with the depth to a saturated zone. Precipitation events influencing groundwater at the time of landslides included a rain-on-snow event in 1982 and an unusually deep snowpack in 1983. The majority of landslides occurred in response to the rain-on-snow event. This long-duration precipitation event included peak intensities of 1.4 to 1.8 cm per hour supplemented by snowpack losses equivalent to 13 cm of runoff. Even snowmelt from an unusually heavy snowpack produced significantly fewer landslides

Language: en

Keywords

FLOW OF WATER - Underground; LANDSLIDES; METEOROLOGY - Atmospheric Precipitation; SOILS - Moisture