The MacDill Air Force Base (AFB), located on an exposed peninsula at the northern end of Tampa Bay, faces shoreline erosion and flooding challenges that are likely to worsen due to changes in sea levels and the increase in storminess. To combat these challenges, the AFB is exploring the implementation of nature-based solutions (NBS) using beneficial use of dredged material to protect AFB assets and support/enhance the ecosystem and habitat fronting the base. The NBS being considered include restoring the historical longshore bar system, expanding existing submerged shallow shelf habitat, and creating barrier islands.

To support the alternatives evaluation, and inform engineering and design, a process-based numerical model was developed, calibrated, and used to simulate representative conditions for the environments around the base. A coupled Delft3D FM hydrodynamic-wave-sediment transport model was developed and calibrated for the Tampa Bay estuary, with a focus on the area near the AFB. The model captures the necessary physical processes to enable the creation of quantitative metrics, supporting a novel approach developed and implemented for this project that follows the principles of Structured Decision Making (SDM). This approach is a transparent and objective-oriented method for identifying actionable alternatives for complex problems involving multiple interested parties or objectives. Specific metrics were developed to support objectives around the physical system. To evaluate which alternatives reduced wave energy at the shoreline fronting the AFB, we assessed cumulative wave energy per unit area across a range of conditions (e.g., tropical and non-tropical, like cold fronts and quiescent periods) throughout the model domain, allowing for a straightforward comparison between alternatives. We simulated tropical storms to quantify flood extent, depth, and duration. For avian habitat metrics, multi-species water depth thresholds were used to identify the monthly spatial extent of suitable avian habitat, including nesting habitat, and non-breeding foraging habitats.  Model outputs will be used to inform NBS selection, engineering and design, and permitting.

This talk will discuss the development and calibration of the hydrodynamic model, detailing how the model was used to compute specific metrics for the SDM process, as well as the and present modeling and metrics results for selected/refined NBS alternatives.