In coastal areas, extreme hydrological events such as floods can be worsened by sea level rise, increasing water table elevations, and decreasing the energy gradient of outflows. In that context, Alabama State Route 180 (AL-180) in Baldwin County, Alabama, which serves as a local evacuation route, is vulnerable to severe coastal storms. The study analysis aims to assess road exposure to inundation, exploring alternatives to incorporate the effects of groundwater and tides. An ongoing numerical investigation is applying the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) tool to allow for a localized analysis of the interaction of overland and shallow groundwater flow in small catchments formed on the sides of AL-180. Because the areas contributing to flow are small (less than one km²), the flow accumulation threshold for this case study was 0.01 km². In addition, high-resolution elevation data (0.5 m lidar) have been used along with locally-collected rainfall data. Preliminary results confirm a hypothesis that high groundwater was generated as a response to extreme rain events, which in turn increased the intensity and duration of flooding. These results indicate the extension and duration of flooding over pavements during intense rain events. Future research steps will consider Richards’ equation-based alternative to represent subsurface flows and include systematic changes in water table elevation combined with rainfall scenarios. These changes will improve the assessment of the unsaturated zone moisture, which in turn will be useful to investigate the potential impact on the pavement subbase.
