addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsIdentify Potential Climate Consequences and MagnitudesWith potential exposure to climate impacts established for a limited selection ofassets, an assessment of consequences can commence. The previous moduleconsidered the magnitude of potential consequences as a means by which to helpscreen the universe of transportation infrastructure down to a manageablenumber of high risk assets. The consequences assessment recommended inModule 4 involves the creation of a pathway to expected consequences. Theexposure assessment constitutes the first segment of the pathway – starting withthe stressor of concern and proceeding to potential climate impacts based onasset susceptibility. For example, extreme rainfall → increased stream flows →bridge scour, especially for bridges that already suffer from a scour condition(are scour critical). Since susceptibility was previously established through rulesof thumb, agencies may wish to adjust impact susceptibilities based on actualasset characteristics, including condition (or expected condition), if applicable.This may be accomplished in a variety of ways, including consultation withinfrastructure managers, but should balance confidence in the results with thetime required to make the determination. To illustrate a potential susceptibilityadjustment, if the Module 3 assessment identifies a bridge impacted by aflooding event, a closer look in Module 4 might indicate that the deck would bespared overtopping, but that the approaches would likely be inundated, forinstance, or that erosion might affect the abutments.The next step in the pathway is to consider what consequence exposure is likelyto have on a given asset. The objective of this exercise – as with all precedingexercises – is to leverage professional knowledge (especially concerning currentconsequences of similar impacts) and existing assessment techniques to establishthe range of reasonable consequences. To continue with the previous example, ifa bridge’s approaches are expected to be inundated by the one-percent chance(or future one-percent chance) flood event, would the event cause temporarydisruption, lead to advanced deterioration, and/or damage the structure?Consequences can be considered through a variety of lenses. Three broadcategories of consequences cover most eventualities, at least pertaining to theasset itself (other consequences, like loss of life, could be considered as well, butmay be even more challenging to assess). Some impacts may have multiplepossible consequences, while some may not have any notable consequences atall:No Impact. Although most “no impact” asset/stressor combinations willhave been screened out by this point, closer examination could show thatimpacts are actually highly unlikely. When a “no impact” finding is made,the asset/stressor combination need not undergo further assessment.Disruption. Operations may be disrupted or impeded, either temporarily orpartially (as with lane closures), by climate impacts. Slower travel speeds,poorer levels of service, and lower capacity are all examples of partialdisruptions.12-6 Cambridge Systematics, Inc.