Integrating Storm Surge and Sea Level Rise Vulnerability Assessments and Criticality Analyses into Asset Management at MaineDOT
This report presents the results of a Climate Resilience Pilot Project conducted by the Maine Department of Transportation and sponsored in part by the Federal Highway Administration. The project developed and implemented tools to prioritize vulnerable transportation assets in the face of rising sea levels and increasing frequency and intensity of coastal storm surge events. State-owned roads, bridges, and culverts were selected and ranked according to criticality and sensitivity metrics developed in reference to agency maintenance records, flooding histories, and the prioritization efforts of agencies in other states. For the highest priority assets in the towns of Scarborough, Bath, and Bowdoinham, alternative engineering designs were created that would be expected to be resilient to 3.3' and 6' of sea level rise. Depth damage functions were created for these designs and for the existing structures. The T-COAST software was then used to evaluate relative cost-efficiency of the designs in each location under a range of sea level rise and storm surge scenarios, and compare it to replacing each asset in-kind. Cost efficiency inputs included initial construction costs and cumulative expected repair costs over time given agency maintenance records, the depth damage functions created, and the sea level rise curves and storm surge scenarios selected. Results show which candidate designs would be the most cost efficient in each location and demonstrate there is no one correct design for the 3.3' or 6' sea level rise scenarios, even for similar asset types in adjacent towns. Local hydrology, topography, and tidal and storm surge regimes demand a site-specific approach to benefit-cost analysis of alternative engineering structures, at the conceptual design phase. Results also help identify relative contributions of risk from sea level rise and storm surge for each candidate design in each location, and provide insights about how to evaluate agency planning, budgeting, scheduling, and design procedures in an era of both rising sea levels and changing storm surge intensities and probabilities.