Effects of Predicted Large Intensity Storms on Moisture Conditions and Stability of Engineered Slopes

Resiliency of slopes adjacent to linear transportation infrastructure is critical in maintaining commerce, mobility, and public safety. Slope failures are often triggered by changes in the soil moisture regime that can be the result of severe precipitation events. Traditionally, design storm events have been based on historic data that has been used to determine return periods or annual exceedance probabilities of certain intensity storms. However, climate change is generally expected to bring precipitation of varying intensity and erratic frequency. Thus, the assumed moisture conditions used to analyze many engineered slopes may not be realistic for future scenarios, and the effect on stability is not well known. This paper investigates the effects of higher intensity storms on the moisture conditions and stability of engineered slopes. A 2D transient seepage and limit-equilibrium stability model was developed using commercially-available software. The model was then calibrated using data from the instrumented embankment at the Biological & Engineering Impacts of Climate Change on Slopes (BIONICS) facility at Newcastle University, UK. Synthetic design storms representative of 2050 and 2100 precipitation events were created in line with CMIP5 projections, as well as a historical baseline storm. The precipitation events were applied to the model to determine the groundwater and stability effects of the larger intensity storm events. Results indicate minimal impact on overall slope stability despite increased precipitation intensity.