Perimeter Protections: Preliminary Findings by the Dutch Dialogues Team

Few would argue that the Charleston peninsula needs a comprehensive strategy for combating sea level rise and persistent flooding. The Army Corps' recommendation is a perimeter sea wall stretching from Magnolia Cemetery all the way around to the Wagener Terrace neighborhood. HCF supports that approach with the caveat that the wall not only protects the city, but also integrates with its historic fabric and the city’s ongoing flood mitigation projects.This is why HCF has been so heavily involved and led the private sector effort to engage the Waggonner & Ball team (who led the Dutch Dialogues Charleston initiative) to conduct an independent analysis of the Army Corps study and to assist the city in developing the best strategy for navigating this complicated process. The Waggonner & Ball team are experts not only in Charleston's flooding problems, yet also in working with large-scale Corps projects.Their full report will be released during a City Council workshop in February, yet HCF's key takeaways from the initial findings include:

• The city should not get boxed in to a rigid concept this early in the process, and we need to maintain a certain degree of flexibility. The alignment of the wall should reflect the city’s priorities and allow for a range of possibilities based on historic and environmental concerns. This will also allow for better integration with the city’s increasing stormwater issues.
• Pursue improvements to the project through mitigation measures in order to leverage federal funds so that the city is not 100% responsible for costs of those improvements.
• Develop an integrated water-based master plan with clearly delineated goals and priorities. This recommendation comes from the Dutch Dialogues Charleston Final Report, and will address risk, storage, infiltration and drainage performance and identify land use policy, infrastructure projects and policy changes to achieve water management goals. HCF has recommended that this water plan be included as part of the city’s new comprehensive land use plan currently under development.
• Communication and transparency are key, particularly given the stakes of such a huge infrastructure investment. The city must develop a strategy for community and stakeholder engagement at every step in the process, as well as improve internal coordination across city departments.

In their analysis of the proposed sea wall, the Waggonner & Ball team worked alongside City staff and the Army Corps project team to review the project outcomes to date and make a technical analysis. Importantly (and something that HCF recommended in our comments to the Corps last spring), the team divided the peninsula into logical sections and tailored their analysis and design criteria for each phase.The Scope of the W&B Analysis:

• Identify gaps and risk concerns with the plan (water overtopping the wall, ability to adapt the wall for future sea level rise, internal stormwater management, need for a full Environmental Impact Statement, etc.).
• Recommend a range of wall alignment options as the project continues to develop and consideration of alternate construction phasing.
• Identify additional approaches not included in the plan, such as road elevation and nature-based solutions.
• Develop initiatives to the help the city strategically engage with the Corps and the broader public.
• Assist the city to better understand Corps project milestones and how to assert city priorities in advance of those.

According to the National Weather Service Coastal Flood Event Database, 2019 and 2020 produced the highest number of tidal flooding events on record for the Charleston Harbor. Collectively, increased tidal flooding events like we’ve experienced these past two years, increasing storm frequency and intensity, and the reality of sea level rise mean that Charleston must weigh every measure to preserve our city, especially if we can secure significant federal funding. HCF continues to view this Army Corps project as a massive opportunity to protect the peninsula for the long term.