Transportation infrastructure intersects challenging terrain that can negatively impact integrity. Minnesota’s climate, geomorphology, and steep terrain along rivers increase the incidence of slope failures such as rockfalls and landslides. WSB was contracted by MnDOT to determine the risk of slope failure along state highways in districts 6, 7, and the Metro. This report outlines the methods and results of the MnDOT Slope Vulnerability project including a new Geographic Information Systems (GIS) model that can be implemented anywhere in the state.
The model contains three main parts: 1.) identify past slope failures, 2.) model the causative factors of past slope failures and how they vary locally, 3.) model the risk of new slope failures. Vulnerability factors including slope, terrain curvature, proximity to rivers, and proximity to bedrock outcrops were statistically tested to determine their capabilities in causing slope failure. Field verification results validate the model’s capability of identifying risk in regions with different geology, geomorphology, and hydrology.
Model results were ranked into four risk management categories: action recommended, further evaluation, monitoring, and no action recommended. Risk incorporates the model outputs with consequence to infrastructure including distance to roads and populated areas. Results indicate that 826 of the 35,000 “management areas” delineated and ranked in GIS are recommended for mitigation. Next steps include field visits and a site-specific mitigation program. The results of this study are intended as the first step of actions required in minimizing the effects of slope failure including expensive mitigation and maintenance repairs and threats to public safety. View the report at https://www.dot.state.mn.us/research/reports/2019/201912.pdf