Tidal and Inland Related Flood Risk Management Study

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Tidal and Inland Related Flood Risk Management Study

The U.S. Army Corps of Engineers, Charleston District and the city of Charleston are conducting a feasibility study for a project for tidal and inland-related flood risk management for the city of Charleston, and based upon the study, different structural, non-structural and natural/nature-based features will be recommended to reduce the risk of flood damages.

Study Authority

The Tidal- And Inland-Related Flood Risk Management study was authorized by Congress in the Water Resources Development Act of 2020 (Public Law 116-260). The authority directs the Secretary of the Army, acting through the USACE, to develop a comprehensive plan to determine the feasibility of carrying our projects for flood damage reduction in the City of Charleston.

Project Area

Charleston is the most populous city in the U.S. state of South Carolina, the county seat of Charleston County, and the principal city in the Charleston metropolitan area. The city lies just south of the geographical midpoint of South Carolina's coastline on Charleston Harbor, an inlet of the Atlantic Ocean formed by the confluence of the Ashley, Cooper, and Wando rivers. Charleston had a population of 150,227 at the 2020 census. The population of the Charleston metropolitan area, comprising Berkeley, Charleston, and Dorchester counties, was estimated to be 849,417 in 2023. It ranks as the third-most populous metropolitan statistical area in the state, and the 71st-most populous in the United States.

Problem Statement

Low lying coastal communities including residential populations, commercial and tourism centers and a regional medical center are becoming increasingly vulnerable to inland and tidal flooding that, when combined with increasingly intense precipitation and relative sea level change can result in life safety risk and economic risks from tides and rainfall events. High demand for residential and commercial developments drive continued growth of the built environment that replaces pervious surfaces with impervious surfaces, displace wetlands and constrain the capabilities of the built infrastructure and natural marshes and habitats to detain or convey water. Higher probability of widespread and longer duration inland and tidal flooding endangers the nationally significant historic and cultural assets within the study area.

Frequently Asked Questions

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How are the City of Charleston and other stakeholders involved?

With this study, the city of Charleston, Army Corps of Engineers and other stakeholders will work together to develop possible alternatives to alleviate tidal and inland flooding across the city. The study’s objective will be to find the most effective way to reduce the risk of damages from tidal and inland flooding events and provide the best return for the federal investment.

How can the public get involved?

Public input is integral to our process. The public will have several opportunities to get involved during the initial scoping period (first 6 months), through multiple public meetings throughout the study and during the comment period of the draft report.

How does this study incorporate into the city’s other flooding projects?

The city of Charleston has already taken significant steps to combat flooding and we commend their proactive approach. This study will consider the measures that have been completed and are currently in progress including the design of the current Peninsula CSRM project.

How is the study/project funded?

The U.S. Congress recently authorized a Tidal and Inland Flooding feasibility (3x3x3) study for the entire city of Charleston, to be cost-shared 50 percent by USACE and 50 percent by the city. The cost-sharing agreement with the city of Charleston for the Tidal and Inland Feasibility Study is in the works, with plans for signing an agreement early in 2024. USACE received partial funding in 2023 to start the study; City Council will be asked to approve the City’s cost-share soon. The study will start after the agreement is signed.

What is the budget/schedule for the study?

The budget and schedule will be finalized once we understand the full scope of the study.

What is the scope of the study?

Preliminary scoping of the Tidal and Inland study will begin in early 2024, after a signed agreement with the city of Charleston. The focus areas for the study are areas that will be vulnerable to tidal and inland (rainfall) flooding within the city of Charleston.

Is the study going to solve the city’s flooding problems?

The Army Corps of Engineers’ Tidal and Inland study is one piece of an overall comprehensive flooding strategy for the city of Charleston, and our team of engineers and technical experts are determined to do everything we can to help in this effort. In the last few years, the city has rolled out several flood mitigation actions, including its Flooding and Sea Level Rise Strategy, a vulnerability assessment, rehabilitation of Low Battery Wall, Dutch Dialogues and major drainage projects.

Why is this study important for Charleston?

Coastal (tidal and storm surge) and inland (rainfall / storm water) flooding are common in Charleston and the Lowcountry. Sea level rise, however, combined with more dynamic weather will substantially shift the frequency, duration and impact of coastal and inland flood events over the next 30 years. Without ongoing and additional risk reduction and land use policies, projects and related investments, Charleston will face increased flood damage and impacts.