Delaware Inland Bays and Delaware Bay Coast Coastal Storm Risk Management Study

The Delaware Inland Bays and Delaware Bay Coast (DIBDBC) Coastal Storm Risk Management Study (CSRM) will explore potential small and large-scale Delawarean storm risk management problems and flood risk reduction solutions. The feasibility study will recommend coastal storm risk reduction solutions which increase community resilience to coastal storms for implementation.

The Delaware Inland Bay and Delaware Bay Coast have historically endured many coastal storms. In addition to the immediate flooding, power-outage, and safety risks that occur during coastal storms, Delaware’s coastlines have also experienced long-lasting impacts such as public and private infrastructure damage, marsh degradation, sand dune degradation, habitat impacts, road closures, etc. Climate change is not only increasing the frequency of destructive coastal storms, but also causing sea level rise which will further increase the flood risk for coastal Delaware.

In order to help reduce the risk of future coastal storm impacts on Delaware’s coastlines, the Delaware Department of Natural Resources and Environmental Control (DNREC) is partnering with the U.S. Army Corps of Engineers (USACE) to complete a feasibility study investigating CSRM problems and solutions. A USACE feasibility study involves “assessing problems and opportunities related to water resources, coming up with alternative solutions to address those problems, comparing those solutions and, ultimately, recommending the solution(s) that makes most sense.” This study is a continuation of the USACE North Atlantic Coast Comprehensive Study (NACCS), and uses the NACCS framework for CSRM investigations. The study may include portions of the Delaware Inland Bays as well as the Delaware Bay coastline. This webpage will be updated with specific study scope areas when the information becomes available.

The study will include three overarching efforts:

  1. The study area’s coastal flood problems and future flood conditions will be defined and assessed
  2. The feasibility of installing system-wide solutions will be defined and assessed
  3. The feasibility of installing site-specific solutions will be assessed

The USACE study process involves identifying problems under current and future conditions; gathering data; identifying and evaluating alternatives that can address the problems; and ultimately recommending a plan. Alternatives are assessed to determine if they are feasible from an engineering standpoint, a cost-justification standpoint, and environmental standpoint.  

USACE will conduct the study objectively, consider all input, and analyze alternatives with sound science. Any proposed changes must be economically justified, environmentally acceptable, and technically sound. It is worth noting that some USACE studies result in a no-project recommendation; some result in  a recommended plan but don’t get authorized by Congress; and some studies/recommendations get authorized by Congress but are not funded and do not get built or implemented.

Study Kickoff - Feasibility Cost Sharing Agreement Signed by USACE and DNREC - November 2022

Phase 1 (January 2023 – April 2023): Study Scoping

  • Establish study geographical scope
    • Note that although the study’s authority includes large swaths of coastline, the first step is to substantially narrow down the geographical scope to focus on areas this study can have the most impact.
    • If you have information regarding flooding issues in your community and/or flooding/hazard studies in your community, please leave a comment in the comment box at the bottom of the page.
  • Establish existing conditions and future conditions
  • Identify and evaluate potential Coastal Storm Risk Management solutions

Phase 2 (April 2023 – January 2024): Alternative Evaluation & Analysis and Tentatively Selected Plan

  • Compare and evaluate focused selection of Alternative plans. In USACE studies, an “Alternative” is a project element that is “capable of being done after taking into consideration cost, existing technology, and logistics in light of the overall project purpose(s)”.
  • Identify the Tentatively Selected Plan (TSP)

Phase 3 (January 2024 – July 2024): Tentatively Selected Plan Review

  • Draft feasibility report based on TSP
  • Release the feasibility report for internal and public review
  • Public meeting on contents of the draft feasibility report
  • Address reviewer comments and  confirm and/or modify the TSP prior to the selection of the final plan
  • USACE endorses the selected plan

Phase 4 (July 2024 – July 2025): Feasibility Analysis of Selected Plan

  • Feasibility-level design and plan optimization
  • Final Feasibility Report is forwarded for Washington-level review

Phase 5 (July 2025 – January 2026): Washington-level Review

  • Final review of feasibility report
  • Revisions to the final feasibility report and the chief’s report (if applicable)
  • Chief's Report is signed (if applicable)
  • Study is complete

The U.S. Army Corps of Engineers (USACE; includes team members from both the Philadelphia District and the Baltimore District) is managing the overall study. The Delaware Department of Natural Resources & Environmental Control (DNREC) serves as the non-federal sponsor for the study. The total $2 million study funding comes from a 50/50 cost share between USACE and DNREC. This funding covers the cost of the study, not the implementation of the study recommended solutions. Funding for the implementation of the study-recommended solutions is not limited to state or federal funding sources.

Though the authorized study area initially included Inland Bays and Delaware Bay shorelines, the study scope needed to be refined. The data-driven down-scoping considered existing or ongoing coastal flood mitigation studies, population and critical infrastructure at risk to coastal flooding, and equity opportunity areas, in addition to other technical data. The study area was refined/down-scoped to align with the budget, time considerations, and other factors.

The project team have determined that the focus area of the study will be the Delaware Inland Bays area, including watersheds around Rehoboth Bay, Indian River Bay, and Little Assawoman Bay. The study will focus on developing solutions to coastal storm flooding and is not necessarily going to produce solutions to sunny-day (nuisance) flooding or rainfall drainage issues. Sea level rise will be incorporated into the study in order to plan for a more resilient future.

The Inland Bays area was selected for the following reasons:

  • The high number of critical structures that are essential for everyday life within the 1-percent-annual-chance (100-year) floodplain (e.g. police stations, fire stations, schools, daycare centers, hospitals and other healthcare centers, roadways, evacuation routes, fueling stations, etc.).
  • The high number of residential and commercial structures within the 1-percent-annual-chance (100-year) floodplain.
  • The number of underserved communities within the 1-percent-annual-chance (100-year) floodplain. Underserved communities are communities that include a high proportion of residents in poverty and a high proportion of Black or Hispanic or Asian or American Indian residents.
  • The high frequency of flooding events affecting the Inland Bays area.
  • The remaining uncertainty about local coastal flood issues and potential solutions.
  • The low number of coastal models necessary to analyze this study area.

Comment on the Delaware Inland Bays and Delaware Bay Coast Coastal Storm Risk Management Study