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



The Coastal Storm Risk Management Study of the Delaware Inland Bays and Delaware Bay Coast (known as the Back Bay Study) will explore potential storm risk management problems and flood risk reduction solutions. It will recommend risk reduction solutions that increase community resilience to coastal storms.

Storm-driven waves break over wooden docks extending into a salt-water bay.

Delaware’s Inland Bays and Delaware Bay Coast have endured many coastal storms. Storms have brought flooding, power-outages and safety risks. They have had long-lasting impacts such as infrastructure damage, marsh and sand dune degradation, habitat impacts, and road closures.

Climate change is increasing the frequency of destructive coastal storms. And it is causing sea level rise, which will further increase the flood risk for coastal Delaware.

Project Overview

Logo of the Us Army Corps of Engineers

To help reduce the risk of coastal storm impacts, DNREC is partnering with the US Army Corps of Engineers (USACE) on a feasibility study investigating coastal storm risk management problems and solutions.

The study will assess flooding problems and identify possible solutions. It will compare the possible solutions and recommend those that make the most sense.

The study is a continuation of the Corps’ North Atlantic Coast Comprehensive Study (NACCS). It uses the NACCS framework for coastal storm risk management (known at the USACE as CSRM) investigations.

The study will include three overarching efforts:

  • Define and assess the study area’s coastal flood problems and future flood conditions.
  • Define and assess the feasibility of installing system-wide solutions — large-scale community-level solutions such as storm surge barriers and tidal gates.
  • Assess the feasibility of installing site-specific solutions — smaller projects such as structural, nonstructural, natural and nature-based solutions.

Inputs

Comments and Questions

Submit comments or questions to Nicole Marks

The study will consider geospatial data, engineering models, ecological data, an economic inventory and public input.

It will use existing models, data and studies from other Corps of Engineers projects as well as other coastal storm risk and resilience studies, projects, and initiatives from Federal, State, and local agencies.

Final Products

There will be two final products of the Coastal Storm Risk Management Study.

A Feasibility Report of final recommendations for projects. It will include plans for implementing the recommended solutions and engineering analyses. It will list decision-making criteria to help identify the best set of coastal storm risk management solutions.

A USACE Chief of Engineers Report (Chief’s Report) for those projects that meet or exceed the Corps’ feasibility criteria. This report will be used to seek Congressional approval to continue developing the projects. A Chief’s Report is an important step toward authorization, appropriation, and implementation of a project.

Study Scope

A map of southeastern Sussex Co. Delaware, with a red line drawn around the Inland Bays area.

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.

Funding 

Funding for the study ($2 million) comes from a 50/50 cost-share between the state of Delaware and the Corps of Engineers. This funding covers the cost of the study, not the implementation of the study-recommended coastal storm risk management solutions. 

Funding for possible implementation is not limited to state or federal funding sources.

Project Timeline

Phase 1: Study Scoping (Jan. 2023 – April 2023)

  • Establish geographic scope to focus on areas where the study can have the most impact. Please share information regarding flooding issues and/or flooding/hazard studies in your community.
  • Identify and evaluate potential coastal storm risk management solutions 
  • Establish existing conditions and future conditions 

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

  • Compare and evaluate focused selection of Alternative plans. 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

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

  • Draft feasibility report based on tentatively selected plan.
  • 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 Tentatively Selected Plan prior to the selection of the final plan.
  • Corps of Engineers endorses the selected plan.

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

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

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

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



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