Landslide hazard rating system for Colorado highways, A

Abstract

This thesis presents the Colorado Landslide Hazard Rating System (CLHRS), a framework for quantifying landslide risk as it applies to highways in the state of Colorado. A preliminary version of the CLHRS was developed based on a review of the current body of technical literature regarding the factors that contribute to landslide hazard, consequence, and risk. The preliminary CLHRS consisted of 11 Hazard Factors and 8 Consequence Factors that were used to calculate an overall risk score. The preliminary CLHRS was used to evaluate 69 landslides distributed throughout western Colorado. The resulting scoring distributions were subjected to a suite of statistical analyses in order to facilitate data screening and identify the factors that possessed the greatest statistical merit. Descriptive statistics were used to establish severity category breaks for hazard, consequence, and risk. Evaluation of the distribution of scores for each factor as well as correlation analysis, ordinal logistic regression, and stepwise regression were used to eliminate factors that lacked sufficient predictive power. Cluster analysis was applied as a secondary method for establishing boundaries on severity categories and compared to the descriptive statistics method. The data screening steps allowed for the creation of a final functional version of the CLHRS consisting of 6 Hazard Factors: geology, vegetative cover, slope aspect, surface water influence, failure frequency, and slope angle, and 6 Consequence Factors: depth to slide plane, length of highway affected, average daily traffic, detour options, worst-case scenario detour time, and annual maintenance cost. Linear regressions comparing the 19 parameter system to the 12 parameter system indicate that consistent patterns in total score distributions are maintained. Furthermore, comparisons of the landslides with the highest risk scores to their respective case studies further corroborate the findings of this research.