Sea-Level Rise: A Transportation Vulnerability Assessment of the Wilmington, Delaware Region
This assessment was prepared by the staff of the Wilmington Area Planning Council (WILMAPCO), the Metropolitan Planning Organization for New Castle County, Delaware and Cecil County, Maryland, to identify the vulnerabilities of the area’s transportation infrastructure to climate change. The body of the report is broken into five chapters: background, methodology, regional impacts, cluster (neighborhood level) profiles, and policy recommendations.
Chapter 1 provides background information on climate change, sea-level rise (SLR), local vulnerabilities and impacts, and current adaptation planning efforts. It emphasizes that the Mid-Atlantic region experienced substantially greater SLR than the global average during the 20th century, “primarily due to the low-lying landscape and slope grade in and around the Chesapeake and Delaware Bays and other geologic changes resulting from post-glacial rebound.” Potential impacts identified for the region include extreme events like hurricanes and nor’easters, as well as chronic problems including shoreline erosion, coastal flooding, storm surge, and inundation. The chapter concludes with a discussion of how these impacts can disrupt transportation networks and block evacuation routes, and how adaptation planning is beginning to cope with these threats.
Chapter 2 describes the methodology used by the Steering Committee to guide the development of the study and the Geographic Information Systems (GIS) analysis that was completed. The study used six inundation scenarios, three for each county, supplied by the Delaware Department of Natural Resources and Environmental Control (DNREC) and Maryland State Highway Administration. DNREC’s data for New Castle County showed potential for land submerged by 0.5 meter (1.6 feet), 1.0 meter (3.3 feet), and 1.5 meters (4.9 feet), while Maryland’s data for Cecil County showed possible rise of 2 feet, 5 feet, or a 10 foot surge scenario.
Chapter 2 also discusses the base data on road and rail networks, bridges, and other elements of transportation infrastructure, which was overlaid with the inundation scenarios to assess potential impacts. The chapter closes by describing the “Critical Roadway Impact Index” that was developed to score the 566 identified at-risk road segments. Points were awarded based upon risk of inundation under different rise scenarios, the surrounding demographics, and traffic characteristics.
Chapter 3 provides an overview of regional impacts to transportation infrastructure as a result of SLR under the six selected inundation scenarios. It indicates that major population centers, including Wilmington, the City of New Castle, Delaware City, and the towns of Elkton, Chesapeake City, and North East are vulnerable to SLR. This section identifies vulnerable road segments such as SR 9 and US 13 along the Delaware River and SR 222 along the Susquehanna River, which are at-risk of increased flooding or complete inundation if no action is taken. A number of maps and tables are presented providing detailed information on projected inundation. Key findings include:
- Over 30 miles of road, 2.7% of the total, face inundation under at least one scenario.
- About four miles of the evacuation system, 1.4% of the total, is vulnerable to SLR.
- Almost nine miles of rail, about 5% of the total, are at risk under 1.5 meters (5 foot) of SLR.
- 117 bridges and overpasses could be affected by 0.5 meter (2 foot) of SLR.
Chapter 4 provides 20 “cluster profiles” that assess the neighborhood-level impacts of SLR by census block groups. It indicates that the size and extent of SLR impacts vary across the clusters. Roughly a half dozen clusters show minimal inundation, while the remaining clusters are subject to widespread flows. The infrastructure and planned projects that are at risk of inundation also vary considerably, depending upon the location, topography, and proximity to existing waterways. The chapter presents a series of maps that indicate the vulnerabilities of existing assets and planned projects within each cluster under the three applicable inundation scenarios.
Chapter 5 presents four broad policy recommendations for addressing the vulnerabilities identified in the study. These include: incorporating climate change mitigation and adaptation policy into the next Regional Transportation Plan (RTP); continually monitoring SLR impacts to planned projects, including an update of this assessment with improved inundation data in 2016; enhancing climate change public outreach; and supporting ongoing climate change adaptation and mitigation efforts.
WILMAPCO completed an update to its RTP in 2015 and incorporated the findings from this assessment in the update. In RTP 2040, one of the objectives identified under the overarching goal of supporting sustainable economic development and goods movement is to plan for energy security and climate change. Understanding and adapting to SLR is one of the action items within this objective, and the RTP identifies qualitative review of UPWP and assessing vulnerability of infrastructure and planned projects as potential performance measures. The RTP incorporates SLR scenario maps for the area and an overview of potentially impacted roadways and railways. The full assessment is also included as Appendix S to the RTP update. Appendix T to the RTP update includes a list of specific planned projects that are vulnerable to SLR, identifying the lowest scenario (of the six SLR scenarios used in the vulnerability assessment) at which the project would be impacted. It is intended to provide a preliminary assessment of potential impacts to highlight projects that should consider SLR impacts more fully during the project development phases.
The SLR vulnerability assessment was supported by funding from Federal Highway Administration and the Federal Transit Administration.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on October 26, 2015.
Publication Date: July 2011
- Wilmington Area Planning Council