A risk-based assessment tool to prioritize roadway culvert assets for climate change adaptation planning
Wall, Thomas A.
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There is growing concern in the United States and abroad that changes in climate may have serious adverse impacts on communities and their civil infrastructure systems. In response, governments and agencies have begun to investigate adaptation: actions taken to reduce the vulnerability or increase the resiliency of natural and human systems in light of expected climate change. In the transportation sector, adaptation planning has predominantly pursued risk-based strategies that seek to identify climate impacts, and assess infrastructure vulnerabilities across multiple asset types, in network-level planning. However, given the complexity of the myriad asset types of which engineered civil infrastructure systems are composed, these frameworks may not adequately address the unique concerns of these various individual asset types. This research develops a risk-based framework to assess and prioritize at a network-level the risks of highway culvert assets to the projected impacts of climate change, specifically focusing on increases in extreme precipitation, and the associated potential for flooding. The framework is applied in a series of case studies using culvert management data provided by four state DOTs, and national climate change projection and infrastructure datasets. The framework developed proposes a new characterization of infrastructure climate change risk, based upon the catastrophe model, to address the need for qualitative approaches to risk given the uncertain nature of climate change, and the sometimes sparse inventory and attribute data for various assets. This characterization proposes three “dimensions” of infrastructure climate risk (climate change impact exposure, asset climate impact vulnerability, and asset criticality) to assign culvert asset priorities. The research develops a method to project the geospatial extent and changes in magnitude of extreme precipitation events; it also develops two measures of culvert vulnerability to increased flow conditions based upon data collected in general culvert management activities. This research demonstrates that existing data sources can be reasonably combined in an analytical assessment framework to identify climate change impact risks to highway culvert assets, providing an additional resource to the existing climate change adaptation planning and risk management toolkit in the transportation infrastructure sector, and also laying a foundation for further refinement of these methods. The results of this research demonstrate that existing climate change projection data, when used alongside culvert inventory and attribute data, provides a reasonable means by which to analyze the projected exposure of culvert assets to climate change impacts. This research also demonstrates that existing culvert management data provides a reasonable foundation upon which to assess the relative vulnerability of culverts to increased flow conditions, although additional research is necessary to develop these methods. The structure of the proposed framework provides a viable means by which quantitative climate change projections, asset vulnerability, and asset criticality data can be combined in a mixed-methods approach to qualitatively characterize climate change impact risks to highway culvert assets despite uncertainty in climate change projections and other inputs.