MacDill Air Force Base (AFB) faces significant challenges of shoreline erosion and flooding that are likely to worsen in future years. The configuration of the AFB provides opportunities to employ nature-based solutions (NBS) to protect facilities while supporting ecosystem service co-benefits and habitat creation. Potential opportunities for NBS include restoring the historical longshore bar system, expanding existing submerged shallow shelf habitat, and creating barrier islands.

Such actions require substantial planning, cooperation, and coordination across local, state, and federal decision-makers, stakeholders, and regulatory agencies. Early engagement is critical to success, including for environmental permitting. A novel approach is being used here that follows the principles of Structured Decision Making (SDM), a transparent and objective-orientated approach to identifying actionable alternatives for complex problems where there are multiple interested parties. First, facilitated working sessions were held with regulatory and resource management representatives to identify implementation objectives, impediments, and strategies for mitigation; estimate likely NBS outcomes; and identify critical uncertainties. These objectives included maximizing wave and surge attenuation; maintaining or increasing submerged aquatic vegetation (SAV) and other valuable habitat; limiting the potential for bird-aircraft strikes and other security concerns; and minimizing regional erosion. Key uncertainties included the degree to which SAV could be positively or negatively impacted; how NBS would impact the risk of bird-aircraft strikes; and the magnitude of wave attenuation, surge protection, and downstream erosion influence the NBS alternatives would have.

Based on that input, the team identified methods to address those key uncertainties and evaluate alternatives. A numerical hydrodynamic, wave, and sediment transport model was developed, along with analytical approaches to assess the potential impacts of alternatives to SAV and bird-aircraft strike hazards. The initial NBS options were refined into a set of preliminary designs, which were evaluated and assessed with quantitative metrics derived from the analysis. These results were used to consider outcomes and tradeoffs, and to inform the 30% engineering design. We will present the results and the next steps in this ongoing, collaborative process with regulatory authorities and regional stakeholders.