Phase 3 MnDOT Slope Vulnerability Assessments

Status:  Complete
Report Date:  08/03/2020


Phase 3 Slope Vulnerability Assessments is a continuation of Phases 1 and 2 previously conducted by WSB and MnDOT to determine the risk of slope failure along state highways. This phase includes 27 counties located in MnDOT districts 1, 2, 3, and 4. The three main components of the model are 1) identify past slope failures, 2) model the causative factors of past slope failures and how they vary locally, and 3) model the risk of new slope failures. Vulnerability factors, failure types, and model results reflect the geomorphology of this region. Vulnerability factors for the new study area include slope angle, terrain curvature, and water table depth. Field verification validates the model’s capability of identifying risk in regions with different geology, geomorphology, and hydrology including deep-seated slides. Model results were ranked into four proposed risk management categories: action recommended, further evaluation, monitoring, and no action recommended. The risk estimation process for this phase is considered preliminary; further consideration of risk tolerance and consequence definitions should be conducted. Preliminary risk results indicate that 370 management areas, and 3% of the total area falls into the action recommended category under the proposed risk matrix. The results of this study are intended to be the first step of actions required in minimizing the effects of slope failure including expensive mitigation and maintenance repairs and threats to public safety.

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