Preparing for Tomorrow’s High Tide: Sea Level Rise Vulnerability Assessment for the State of Delaware – Transportation Infrastructure

This Sea Level Rise Vulnerability Assessment describes and quantifies impacts of sea-level rise (SLR) on 79 resources in Delaware, including transportation resources. The Assessment discusses projections of SLR for Delaware, defines the method used to determine potential vulnerability to SLR, and provides analysis of each resource category. Among these resources, the Assessment addresses Delaware’s transportation infrastructure, including railroad lines, roads and bridges, and the Port of Wilmington.

As a low-lying coastal state, Delaware is particularly vulnerable to the effects of SLR. Overall, the Assessment finds that between 8% and 11% of Delaware’s land area could be inundated by a sea-level rise of 0.5 to 1.5 meters, respectively. As a result of this inundation, structures built in low-elevation areas could become difficult to access, unstable, or even damaged beyond repair.

The Assessment is based on three planning scenarios for SLR to the year 2100: a low scenario of 0.5 meters, an intermediate scenario of 1 meter, and a high scenario of 1.5 meters. These scenarios were recommended by Delaware’s Sea Level Rise Technical Workgroup, which reviewed local historical tidal data and the findings of international bodies such as the Intergovernmental Panel on Climate Change. The Workgroup was established by Delaware’s Department of Natural Resources and Environmental Control. The study only assesses what will be inundated under the three scenarios; it does not assess temporary flooding from storm events. Past extreme storm events have caused flooding comparable with the high SLR scenario for the state: In 1962 a record nor’easter caused 1.4 meter storm surge in Lewes, DE, and in 2008 a nor’easter caused a 1.2 meter storm surge in Bowers Beach.

As a whole, the Assessment provides detailed information about what resources will be impacted by SLR, where those impacts will occur, and what the likely social, environmental, and economic effects will be. The Assessment was developed in five stages: 1) identification of resources of concern, 2) data collection, 3) exposure assessment, 4) impact assessment, and 5) risk assessment. Each of these stages was informed by a series of public engagement sessions. Because of its large scope, the Assessment is intended as a screening tool for determining the need for more detailed vulnerability assessments and adaptation strategies.

Of Delaware’s transportation infrastructure, the Assessment places the highest concern on the Port of Wilmington, railroad lines, and roads and bridges. For the Port of Wilmington, the Assessment states that between 36% and 73% of the property is within an area that could be inundated by SLR by 2100. Wilmington is the busiest port on the Delaware River, and a major import location for fresh produce. Limited or altered functionality of the port may cause a loss of jobs and revenue to the region.

For railroad lines, the Assessment states that between 2% and 6% are located within an area that could be inundated by SLR by 2100. This is significant because the functionality of an entire rail line could be lost if even a single segment becomes inundated. Major passenger and freight lines are located in Delaware, and disruption of rail service could have economic and social impacts throughout the state and region. Damage to railroad lines from SLR may increase shipping costs for freight and prices for passenger travel. Also, tracks and other facilities would need to be relocated to higher ground. In addition, the disruption of passenger lines may have an impact on job opportunities in Delaware, due to individuals not being able to commute to their place of employment.

For roads and bridges, the Assessment states that between 1% and 5% are located within an area that could be inundated by SLR by 2100. SLR directly affects travel on roadways as a result of flooding, erosion of road bases, sediment removal around bridge support and piers, and reduced bridge clearance. This is significant because damage to an individual section of road could cause regional transportation disruptions, especially if no alternative routes are available. Damage to roads and bridges from SLR may substantially alter commercial traffic, affecting the distribution of goods throughout Delaware.

Delaware’s Sea Level Rise Advisory Committee developed the Assessment. The Committee was established by invitation of Collin O’Mara, the Secretary of the Department of Natural Resources and Environmental Control (DNREC). The Committee’s function was to investigate Delaware’s vulnerability to SLR and provide recommendations about how best to prepare for higher sea levels. The Committee was composed of members from state agencies, local governments, and various non-government organizations. The Committee’s work was split into two phases, vulnerability assessment and adaptation planning. The Assessment culminated the vulnerability phase, and was used to inform the subsequent adaptation phase. During the adaptation phase, the Committee identified opportunities for adapting to SLR and developed the report Preparing for Tomorrow’s High Tide: Recommendations for Adapting to Sea Level Rise in Delaware in September 2013. The recommendations focus on building state and local capacity to adapt, rather than on specific adaptation measures given the diverse levels geographic scales at which adaptation will need to occur. For example, the report recommends increasing coordination and cooperation across the mid-Atlantic region and with USDOT for transportation issues affected by SLR. It also recommends incorporating SLR into Delaware’s Long Range Transportation Plan, DelDOT’s Transportation Operations Management Plans for each county, and Transportation Project Design Manuals, among other transportation-related recommendations.

To encourage action on the findings and recommendations of the Committee, DNREC convened a workshop in March 2014 that brought together stakeholders to develop specific implementation actions for each of the recommendations set out in the 2013 report. Separate work groups identified implementation activities for topic-specific recommendations from the 2013 report, including Transportation & Infrastructure. A September 2014 report provides an account of that workshop, and includes a list of the implementation actions developed by the participants; it is intended to serve as an interim implementation plan.

The Delaware Department of Natural Resources and Environmental Control funded this project through a NOAA grant to the Delaware Coastal Programs.


This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on October 23, 2015.



Publication Date: July 2012

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