addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsFigure 11.1 Conducting a Vulnerability and Risk AssessmentCLIMATESTRESSORDATAASSETINVENTORY &CRITICALITYDETERMINE STRESSOREXPOSUREYESNODETERMINE RISK ORMAGNITUDE OFCONSEQUENCES(CRITICALITY)HIGHMEDIUMLOWESTIMATE LIKELIHOODOF IMPACTS(STRESSOR LEVEL ORFREQUENCY)CONDITION DATA(PRIORITIZED FOR ADAPTATION ASSESSMENT)CHARACTERIZE RISKADAPTATIONSource: Cambridge Systematics, Inc., 2012.11.2 CONDUCTING A VULNERABILITY AND RISKASSESSMENTDetermine Stressor ExposureDetermining potential stressor exposure is the foundation of the vulnerabilityassessment. If an asset is not exposed to the effects of a given climate stressor, itcannot be impacted by it, and that stressor/asset combination need not beconsidered further. For example, it can be fairly assumed that far inland assetsare not – and will not be – exposed to storm surge/coastal flooding events. Inthis case, pursuing an assessment of this asset and stressor combination wouldbe a poor, and unfruitful, use of analytical resources.The first task in determining exposure is selecting the appropriate climatescenario from Module 2b. For each climate stressor, there is a “low” and a “high”projection. In the near future, the difference between these two scenarios is oftennegligible, but as the time horizon extends toward 2100, the range of estimatesincreases. Occasionally, even the expected direction of the trend may differ (forexample, precipitation may increase under one scenario, and fall under another).The issue of uncertainty in the degree and direction of stressor change isunavoidable – and challenging – but should not derail the assessment. It mayhelp to consider these projections as the bookends of the range of reasonableclimate futures.In selecting the preferred scenario (or scenarios), an agency’s tolerance for riskshould be a key factor. Risk tolerance may be uniform across the entiremultimodal transportation system, or may be partitioned by asset or asset types.11-2 Cambridge Systematics, Inc.