addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsstandard of precision is infeasible and unproductive in this application; theuncertainties are too great and the resources required would make a system levelassessment impossible. Instead, the technique described below is orientedtoward a rapid, sketch-level assessment of assets at risk, a selection of which canbe considered with greater rigor in the following module (Module 4).Estimate the Potential Magnitude of ConsequencesThe groundwork for this task will have been performed in Module 2a, whereasset criticality is determined. That designation (e.g., low, medium, high; 1-5,etc.) is carried into this exercise as a reasonable estimate of the potentialmagnitude of consequences from stressor exposure. For example, if an asset ishighly critical, meaning that its contribution to mobility, accessibility, economy,safety, etc. is significant, then the potential consequence of disruption,deterioration, or damage is also high. By making this connection, the assessor isspared the potentially painstaking task of attempting to estimate the range ofactual consequences – which involves a consideration of the complex interactionof stressor and structure characteristics. 20Since potential consequence and criticality are coincident, it should bestraightforward to create groupings of magnitudes (such as “high,” “medium,”and “low”). This can be accomplished in GIS (by selecting critical attributes, suchas volumes, for examples) or, for studies that are smaller in scope, by compilingpreviously generated lists of critical assets. If a large number of assets aredesignated as high consequence/highly critical, the “likelihood of impacts”exercise explained subsequently may help screen the selection down to amanageable set. Otherwise, it may be necessary to further segment the top“potential consequence” tier to reduce the pool of assets for further assessment(in GIS, this may be accomplished by distributing critical attributes by quintilesinstead of quartiles, for example).Estimate the Likelihood of ImpactsEstimating the likelihood of impacts can be one of the most challenging aspectsof the assessment. Stressor frequency or annual probability become moreuncertain as the assessment timeframe extends into the future, and the potentialsusceptibility of a given asset to that stressor is similarly difficult to anticipate –especially when asset deterioration and renewal cycles are considered. Thisapproach recommends deferring these difficulties to the significantly smallerselection of assets to be advanced to the following module. Instead, because the“magnitude of consequences” estimate has already established that this exercise20 For studies that have already limited the pool of assets for assessment (whetherthrough constrained geography or policy decisions), it may be appropriate toincorporate more rigorous assessment techniques from Module 4, as needed.Cambridge Systematics, Inc. 11-9