Climate Change and the Highway System: A Project Level Adaptation Approach

Climate change implications and the associated risk and uncertainty in the design and evaluation of infrastructure is an increasing concern facing system owners and engineering design professionals. This paper provides a discussion of a project-level adaptation design process that provides a context for inclusion of climate change uncertainty. The adaptive design process proposed is for the analysis of infrastructure affected by precipitation, runoff, and flooding, but the basic framework can also be used to evaluate other climate hazards such as sea level rise, urban heat islands, etc. The process in this paper focuses on the flooding of transportation infrastructure, in particular a bridge crossing. However, the process can also be readily modified to analyze other forms of infrastructure including sewage treatment facilities, levees, dams, etc. The adaptive design process is a site-specific, detailed evaluation that relies upon the testing of different project alternatives. Multiple alternatives are to be developed and tested for a range of peak discharges associated with future climate projections and/or error margins in historic precipitation data. The process analyzes each project alternative using hydrologic damage curves that relate asset failure thresholds (and their costs) to specific discharge levels. The damage curves are to be developed by planners, economists, and design professionals based upon sound engineering judgment and an analysis of the implications of failure. The adaptive design process can be utilized as a tool to evaluate the uncertainty in system hydrology due to projected climate changes and/or the error margins in the historic climate record. The adaptive design process concludes with a cost-benefit economic analysis. The economic analysis provides the basis for cross-comparison among the adaptation alternatives. The project alternative with the highest benefit/cost ratios across the range of climate scenarios tested should receive strongest consideration for final design.