US Army Corps of Engineers
Charleston District Website

Charleston Peninsula Coastal Flood Risk Management Study

The Charleston Peninsula Coastal Flood Risk Management Study is a federal feasibility study that investigates coastal storm impacts on the Charleston peninsula. In partnership with the City of Charleston and its stakeholders, the study also explores economically-viable and environmentally-sound solutions to mitigate coastal storm risks. The feasibility study began in 2018 and is 100 percent federally funded through Emergency Supplemental Funding.

This feasibility study is one piece of the City’s overall comprehensive flooding strategy. In the last several years, the City has initiated several flood reduction strategies, including its Flooding and Sea Level Rise Strategy, a vulnerability assessment, rehabilitation of Low Battery Wall, Dutch Dialogues and major drainage projects. This study primarily addresses the risks of coastal storm surges. Working in tandem with other flood mitigation efforts, the study also takes tidal flooding and sea level rise into account in its analysis.

In April 2020, the U.S. Army Corps of Engineers published a draft report outlining study findings and general storm risk reduction measures, including a perimeter storm surge wall with pump stations and nonstructural measures. Over the last several months, the study has used public and agency feedback, as well as results from ongoing modeling and analysis, to continue optimizing the proposed plan. Among some of the plan refinements include removal of the wave attenuator, reducing the project’s initial cost; increasing the sea level rise curve to evaluate more severe SLR scenarios; ongoing modifications to the storm surge wall alignment to reduce costs without impacting benefits; and additional detailed interior hydrological modeling.

  • Draft IFR/EA of April 2020:  The draft Integrated Feasibility Report/Environmental Assessment documents and appendices are below.
  • FAQs:  View Frequently Asked Questions under the "FAQ" section below.
  • Public Workshop:  The City of Charleston held a public workshop for City Council members February 18, 2021 for an update on the project. Watch the full event below and view the presentation here.
  • Study Presentation:  The study team created an interactive site to help visually describe the selected plan, alternatives,, history of peninsula flooring and more.

To contact the Charleston Peninsula Study project manager, send an email here.

City Council Workshop (Feb. 18, 2021)



On Feb. 18, 2021, the U.S. Army Corps of Engineers participated in a virtual workshop hosted by the City of Charleston to present an updated plan for the Charleston Peninsula Study and address council members’ questions. The workshop focused on updating the council on the updated plan for the study. Updates came after continued further analysis and incorporating public comments received in Summer 2020. The full meeting and question-and-answer session were recorded and are available to watch at the above video.

 

Frequently Asked Questions

Collapse All Expand All

The Charleston Peninsula Coastal Flood Risk Management Study is a federal feasibility study that investigates coastal storm impacts on the Charleston peninsula. In partnership with the City of Charleston and its stakeholders, the study explores economically-viable and environmentally-sound solutions to mitigate coastal storm risks. Working in tandem with other flood mitigation efforts, the study primarily addresses the risks of coastal storm surges and considers tidal flooding and sea level rise in its analysis.

Coastal storms on the Charleston Peninsula place people at risk, including the potential for loss of life and declines in public health. The Charleston Peninsula experiences coastal storm surges that adversely affect the economic sustainability of Charleston, including impacts to businesses, organizations and industry; critical facilities and infrastructure; and residents. Coastal storm events also limit access to critical facilities, emergency services and evacuation routes. Historic and cultural resources are at risk of damage due to storm surge flooding.

Currently, the plan proposes a 12-foot NAVD88 perimeter storm surge wall with pump stations and nonstructural measures, such as flood-proofing and home-raising, for the study area. Design and alignment of the storm surge wall are conceptual and will continue to undergo refinement through progressive study phases, should the project move forward. The surge wall would be built to withstand earthquakes and can be elevated in the future.

The study has used public and agency feedback, as well as results from ongoing modeling and analysis, to continue optimizing the proposed plan. Among some of the plan refinements from 2020 include removal of the wave attenuator, reducing the project’s initial cost; increasing the sea level rise curve to evaluate more severe SLR scenarios; ongoing modifications to the storm surge wall alignment to reduce costs without impacting benefits; and additional detailed interior hydrological modeling.

The study is currently in the initial (feasibility) phase of the USACE project delivery process. The ultimate purpose of this 3x3x3 feasibility study is to determine whether or not there is a federal interest in a storm surge solution on the peninsula, and if so, outline a project recommendation.

If the project moves to the Pre-Construction Engineering and Design, or PED, the Corps will work with the City of Charleston and local stakeholders to closely refine project design details, including height, placement and material selection, and prepare renderings.

PED, also known as the Design Phase, is a collaborative effort. Within Federal parameters, the Corps will work with the City of Charleston and local stakeholders, such as Historic Charleston, Preservation Society and many others, on determining design features. The City may propose some additional features to aesthetics and the alignment that would be entirely funded by the City.

Regardless of the final design features of a perimeter storm surge wall, the perceived elevation of the wall will vary depending on the location’s topography (i.e., the above-ground wall height will vary according to whether an area is lower-lying or higher ground).

USACE feasibility studies do not guarantee construction. The USACE project delivery process has several steps before construction, including a finalized feasibility report; the City of Charleston must agree with the recommendation and be willing to accept the local cooperation requirements of a non-federal sponsor; the USACE Chief of Engineers must approve the final feasibility report and submit a Chief’s Report to Congress with a favorable recommendation of the project; Congress must make the decision whether to authorize the project; and, finally, Congress would need to appropriate and the City would have to provide the necessary funds to commence the design phase and later the construction phase of a cost-shared project.

The initial (feasibility) phase of the study is 100 percent federally funded. Future phases, including the Design and Construction phases, require a 35 percent cost-share from the City. This means, the City must fund 35 percent of the total cost of that phase. The cost-share amount is not required upfront and is broken up based on annual requirements over each fiscal year.

USACE will present analysis on potential effects to surrounding communities in Spring 2021. If the analysis determines that adverse impacts to adjacent communities are likely, USACE will assess the need for and appropriate mitigation to address those impacts. Formal USACE recommendations cannot move forward without considering the potential for adverse impacts to adjacent communities.

Natural and nature-based features (NNBF), or green solutions, can be effective for other sources of flooding (tidal, SLR), but alone are not sufficient for storm surge flooding. You can save, restore or enhance the wetlands, and they are very helpful for absorbing wave action and storing water when it gets here, but they will not stop the storm surge. Wetlands do not reduce the height of the surge (the water on top of the tide level). The same is true for living shorelines. While not suitable for coastal storm surge risk reduction, the study recommends a number of green infrastructure practices that the City of Charleston could implement to help with localized flooding.

The Dutch Dialogues Charleston Report provides a large-scale framework for addressing several sources of flooding across the region and contains multiple recommendations. The Corps proposal is one aspect of this framework and would, if implemented, require coordination with all other flood reduction efforts. To learn more about how the Corps proposal works with the Dutch recommendation, view the USACE-Dutch Integration.

No. USACE continues to refine the storm surge wall alignment. During optimization, USACE has evaluated ways to reduce costs without impacting benefits. The actual location of the storm surge wall is not finalized until the Design Phase.

The 12-foot NAVD88 storm surge wall is ultimately designed to mitigate storm surge damages to meet FEMA standards. Areas and structures outside the tentative storm surge wall alignment are on higher elevation or are designed within FEMA’s flood standards. For these areas and structures, the study recommends nonstructural measures, such as flood-proofing and home-raising.

Hurricane Hugo was a Category 4 hurricane when it made landfall just north of Charleston in 1989. In the Charleston harbor, peak storm tides reached 9.4-foot NAVD88, or 10-12 feet above mean sea level. Those tidal heights would not have overtopped a 12-foot NAVD88 storm surge wall.

Public Feedback

Thank you to everyone who has already provided helpful comments!

UPDATE: A public meeting will be upcoming in March 2021.

Contact

To ask a question about the Charleston Peninsula Coastal Flood Risk Management Study, email the study team at chs-peninsula-study@usace.army.mil

Interactive Study Overview