The role of flooding on the activation of landslides on UK Rail infrastructure

Slope instability problems are well understood but the cascading hazards of landsliding associated with flooding are complex. The large landslide at Eden Brow and several slips on the Newcastle-Carlisle line which were triggered/reactivated by flooding in 2014, are good examples of the problems associated with transient high water levels in rivers systems. The interaction of high pore fluid pressures; high rates of toe erosion, high rates of effective rainfall and the effects of rapid drawdown as the flood passes all create a complex and very dynamic set of slope conditions. In this project the inter-relationships between storm events, flooding, and slope instability will be investigated using a combination of field observations, archive data and numerical models to 1) understand the ground conditions and hydrogeology at test sites chosen in conjunction with Network Rail; 2) reconstruct flood evolution and overland flow based on field observations of geomorphology and archive aerial photography; 3) model progressive failure of the slope systems using particle flow code; 4) Identify critical and identifiable physical parameters for a predictive tool to be tested against sites to be held back by Network Rail. We will use the understanding of the flood-erosion-pore pressure interactions to develop a risk based indexing system to rank which elements of infrastructure risk posed by landsliding during different design flood events. Asset owners will then be empowered to prioritise the adoption of strategies that will improve the resilience of critical elements of infrastructure in response to evolving flood risk in a changing climate.