This report has been developed in response to Item 437 (D) of Chapter 2 of the 2024 Special Session I Acts of Assembly (the “Appropriation Act"). The Appropriation Act directed the Virginia Department of Transportation (VDOT or the “Department"), with the assistance of the Virginia Institute for Marine Science (VIMS), to provide an annual update on the status of the “Coastal Virginia Transportation Infrastructure Inundation Study" including: an up-to-date identification of at-risk rural, suburban and urban infrastructure, and planning and options to mitigate or eliminate the identified risks; and a report on what work remains to be completed and estimated time frame for the completion of its work.

In 2019, VDOT’s Virginia Transportation Research Council (VTRC) entered into an agreement with VIMS requesting that VIMS conduct a five-year study to develop a strategy for understanding and addressing sea level rise, land subsidence, and recurrent flooding impacts on existing and planned road infrastructure, as well as how that infrastructure will impact natural ecosystems in Virginia’s coastal zone as the climate changes (the “VIMS Study"). The Appropriation Act, Chapter 51 of the 2021 Special Session I Acts of the General Assembly, and other related legislation prompted VDOT to evaluate the vulnerability of its current and planned infrastructure with respect to changing environmental conditions and evaluate strategies to enhance its resilience. Thus, alongside the VIMS Study, VDOT has independently developed a statewide Virginia Department of Transportation’s (VDOT) Resilience Plan (Version 1.0, November 2022) (the “Resilience Plan"). This report summarizes the overall cumulative progress of the VIMS Study, provides an update on significant findings made since the submission of last year’s Annual Update in December 2023 (“Study Year Five"), and identifies how data from the VIMS Study is being integrated into VDOT’s statewide resilience efforts to manage risks to transportation infrastructure.

In the most recent Study Year Five, which is also the final year of the VIMS Study, VIMS completed the development of a network flooding analysis for Tidewater, Virginia, as defined in Va. Code § 62.1-44.15:68, and the remaining localities of Planning District 8 (collectively, the “Coastal Zone"). The network flooding analysis developed by VIMS measures the inaccessibility of road networks based on flooding intervals of 0.5 feet increments, up to 10 feet of inundation. The analysis classifies the degree of road network accessibility to selected priority destinations (“Source Points") at a minimum flood level of 0.5 feet water depth(*1) on the roadway. Primarily comprised of VDOT’s maintenance facilities, this final set of Source Points was chosen to determine the accessibility of those locations to surrounding impacted roadways needing repair during flood events at various flood level depths. An additional analysis was done in Study Year Five, to include hospitals and health centers as Source Points around the Coastal Zone.

VIMS also completed the development of an interactive viewer during Study Year 5, integrating the results from a flood hazard zone assessment, the completed network flooding analyses, and pertinent VDOT infrastructure information. The interactive viewer displays the anticipated duration of flooding across the land surface under different water depths to show which roads are geographically inaccessible from a Source Point to any given end point until the waters recede to less than six inches of water. This data may be used to inform the understanding of the length of travel delay time associated with flooding scenarios. In addition to the impacts of changing weather conditions on existing and planned road infrastructure, VIMS completed their work on examining the impacts of road infrastructure on the natural ecosystems in Virginia’s coastal zone. In all, the VIMS Study has delivered the flood hazard zone assessment, network flooding analyses, and infrastructure interactive viewer tool, which are being used to inform and advance the strategies in VDOT’s Resilience Plan. The strategies are intended to support the incorporation of resilience in the Department’s transportation planning, project development, delivery, operations, maintenance, and asset management efforts. As recommended by VDOT’s Resilience Plan, VDOT is developing a further statewide visualization and decision support tool to help identify infrastructure that is at risk to coastal and riverine flooding and landslides. The results of the VIMS Study are being directly incorporated into the methodology for this tool, which is currently in development and expected to be completed and released in mid-2025. The submission of this report concludes the VIMS study and the annual reporting required by legislation.
_________________________________________________
(*1) For the purposes of this report, a road is inaccessible when more than 0.5 feet of flooding covers the centerline of the road. The selection of 0.5 feet as the standard is due to model sensitivity/accuracy and the vertical resolution of the lidar.