addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsA Risk Assessment for Five Key Assetsin ChattanoogaAs part of the Chattanooga‐Hamilton CountyRegional Planning Agency’s (CHCRPA)climate adaptation workshop, participantsselected three assets for a vulnerability, riskassessment, and adaptation strategyexercise. For one example, the ChickamaugaLock and Dam, the group determined thatthis asset could be vulnerable to threeclimate stressors: extreme participation,extreme temperature, and tornadoes.During the workshop, participantscollaboratively created a risk assessment andadaptation matrix for this asset (and the twoothers) that identified potential impacts,consequences, frequencies, and adaptationstrategies. Additionally, the group created alist of adaptation strategies that can beapplied to a range of regional transportationassets.Source: Cambridge Systematics, Inc.,December 2012.An extremely critical asset may warrant a higherstandard of risk management than an asset thatcarries little volume, has a high degree ofredundancy, and/or does not provide exclusiveaccess to highly important destinations. Where astandard scenario already exists as a legacy ofprevious vulnerability assessments, the agencymay wish to leverage that work, even if it wasperformed for a different sector.Another approach to the challenge of managinguncertainty is to conduct the assessment usingmultiple scenarios. This process, while moreresource intensive, allows for the testing andcomparison of outcomes stemming from differingscenarios. With a better understanding of therange of potential impacts, consequences, andfrequencies/likelihoods, decision-makers may feelmore comfortable formulating strategies thatbalance risk mitigation and resources. The rightapproach will differ based on the circumstances ofeach agency.With the stressor scenario(s) chosen, two basic testscan be employed to determine stressor exposure,although techniques for applying these tests areopen to significant discretion:1. Geospatial. Exposure can be determined geospatially if the stressor underconsideration is itself geospatial (can be drawn on a map). Such stressorsinclude sea-level rise, storm surge, and inland flooding, although bothtemperature and rainfall projections vary by location and can be representedon a map as well. Since assets too are physical, and are presented with a highdegree of spatial precision in many Caltrans GIS Data Library layers and onother maps (such as floodplain maps), assets and stressors can be overlaid todetermine areas of physical coincidence. This technique, when performed ina GIS, is called an “intersection.” Intersections can be two-dimensional or,preferably, three dimensional where LiDAR or other topographical data isavailable. Where elevations of transportation or flood hazard infrastructureare known, they can be integrated into the GIS to further enhance theaccuracy of the intersection analysis.A buffer zone (an extension of the actual mapped boundaries of stressors andassets) can be applied to increase the results of the intersection analysis. Thismay be warranted when agencies are concerned about underestimation ofexposure, either due to data insufficiency, a perceived under-representationof stressor coverage, or a lower appetite for risk than mapped data cansupport. For example, if an agency is concerned about the future effects ofCambridge Systematics, Inc. 11-3