Storm-Induced Slope Failure Susceptibility Mapping

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A pilot study was conducted to characterize and map the areas susceptible to slope failure using state-wide available data. The objective was to determine whether it would be possible to provide slope-failure susceptibility mapping that could be used by local road and highway officials to understand better where slope failure may occur. This would allow the possibility of taking preventative measures where indicated; or developing contingency plans for areas of likely failure. As a first step; a review of pertinent slope-failure literature was conducted to determine which past studies could offer information or guidance useful for developing the mapping. The review helped identify which methods and factors could be most effectively used in assessing susceptibility to slope failure. Then; using physics-based concepts; and making use of publicly-available topographic; soils; and hydrologic information; an approach was developed for using the data to identify conditions under which slope failure would be likely. This approach was incorporated into a GIS-based model that produced mapping wherein slopes were identified and assigned one of five levels (very high to very low) of slopefailure susceptibility. The model was tested against a relatively small area in Carlton County to confirm that the indicated susceptibility to failure correlated well with locations in which there was observable or documented slope failure. The method was then validated by applying it to small areas in Sibley and Carver Counties where slope failures had occurred. Having validated the underlying physics-based approach; the mapping was then expanded to two Carlton and Sibley Counties.