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Project Summary

Sea level rise and increased tropical storm intensity pose a serious risk to the long-term sustainability of historic Fort Jefferson at Dry Tortugas National Park, Florida. The park is trying to mitigate these effects over time through strategic planning, informed decision making, and responsible investments that consider historical integrity and long-term sustainability of the fort and island on which it was built. 

Background

Located 110 km (70 mi) west of Key West, Florida, in the Gulf of Mexico, the seven small islands and historic Fort Jefferson of Dry Tortugas National Park sit on the front lines of the climate change discussion and decision-making process within the National Park Service. The most pressing climate change issues that could directly affect the resources and operations of Dry Tortugas National Park are sea level rise and increased tropical storm intensity. These two factors pose a serious risk to long-term sustainability of Fort Jefferson, the main cultural resource and the base of all park operations, as well as the other islands and accompanying natural resources of the park. 

For more than 165 years, Fort Jefferson on Garden Key has exhibited incredible resilience to storms and the marine environment of the Dry Tortugas. Still the structure is deteriorating. The fort is a mid-19th century Third System Coastal Defense. It is an unreinforced masonry structure composed of coral concrete faced with brick, with six sides and three tiers. It is surrounded by a 21 m (70 ft) wide wet moat that is separated from the open waters of the Gulf of Mexico by a masonry wall, formally called the counterscarp. The counterscarp sits approximately 2 m (6 ft) above the low water line and 1 m (3 ft) above high tide. The moat and counterscarp were designed to keep would-be attackers at bay and to provide a structural first line of defense for the fort against the sea. 

Throughout the architecture of the fort, there are iron components embedded within the masonry that served various functions, including water collection, supports for catwalks, and, most importantly, protection against enemy fire. In this salt water environment, the wrought-iron has rusted and expanded, pushing the brick apart and causing serious structural damage to Fort Jefferson’s exterior scarp walls; large sections of the fort walls have collapsed into the moat. 

Implementation

Through strategic planning, informed decision making, and responsible investments, the park is trying to mitigate the effects of the environment over time. This approach has resulted in removing the corroded iron shutter assembly components and stabilizing the exterior masonry walls. Preservation and stabilization work on the fort has occurred on an intermittent basis since the 1990s. The moat wall has been worked on intermittently since the 1960s. For both structures, the scope of work has been guided by the amount of available funding. At this point in time, all six sides of Fort Jefferson have received some form of stabilization, but the work is not complete. The main priority for the park is to complete the removal of the remaining iron shutter components embedded in the exterior scarp wall (fronts 3 and 2) and to stabilize as much of the brick work from the top of the parapet to the low water line with selective brick replacement and repointing. The estimated cost to finish these stabilizing measures by 2018 is just under $12 million.

Moving forward with preservation efforts, the park is following the National Park Service Climate Change Response Strategy to address the projected consequences of climate change. The park is also using the National Park Service Climate Change Action Plan as a framework for the development of mitigation and adaptation plans; consideration of alternatives for making decisions based on cost effective actions that deliver results; and development of long-term monitoring and documentation that will contribute valuable data to be considered in the future. This course of action should allow the National Park Service to maintain park operations on-site, comply with the park’s enabling legislation by preserving important cultural resources, provide opportunities for visitor enjoyment, and simultaneously make the fort more resilient to the effects of projected climate change while allowing for future adaptation.

To help in prioritizing park needs and strategic investment planning, the park has looked towards scientific data being produced by groups such as the Intergovernmental Panel on Climate Change and the Southeast Atlantic Coastal Ocean Observing System. The US Geological Survey has completed coastal vulnerability studies of the park. The park also installed a sea level monitoring station at Garden Key in fiscal year 2014 using concessions franchise fee funds; this real-time, on-site sea level data will establish a monitoring baseline and will aid in climate change scenario planning and future decision making. 

Outcomes and Conclusions

Preservation decisions must also consider long-term feasibility of park operations within Fort Jefferson and on Garden Key, historic preservation goals and mandates of the National Park Service, visitor experience, and the overall short- and long-term budgets of the National Park Service. Striving for constant improvement and long-term sustainability through the stabilization efforts, the cultural resources staff and stabilization project team have continued to review and improve specifications and contractor performance with increased project oversight and improved documentation of material performance.

Planning for future repairs to the fort and the moat wall require budget foresight, structural vulnerability analysis, careful historic preservation considerations, and continued incorporation of climate change projections, particularly with respect to local sea level rise and storm intensity. Such decisions must include all appropriate compliance and consultation, and participation by policy, preservation, documentation, interpretation, and other programs from across the National Park Service. 

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This case study is part of the 2015 National Park Service report, Coastal Adaptation Strategies: Case Studies. These case studies initially were developed by park managers as part of a NPS-led coastal adaptation training in May 2012. The case studies follow the format created for EcoAdapt’s Climate Adaptation Knowledge Exchange (CAKE) database, including a list of adaptation strategies. All case studies were updated and modified in September 2013 and March 2015 in response to a growing number of requests from coastal parks and other coastal management agencies looking for examples of climate change adaptation strategies for natural and cultural resources and assets along their ocean, lacustrine, and riverine coasts. 

Citation

Kimball, D., M. Rockman, & K. Clark. (2015). Strategic Planning and Responsible Investments for Threatened Historic Structures, Dry Tortugas National Park, Florida [Case study on a project of the Dry Tortugas National Park]. Excerpted from Schupp, C.A., R.L. Beavers, and M.A. Caffrey [eds.]. 2015. Coastal Adaptation Strategies: Case Studies. NPS 999/129700. National Park Service, Fort Collins, Colorado. Retrieved from CAKE: www.cakex.org/case-studies/strategic-planning-and-responsible-investmen…;(Last updated November 2015)

Affiliated Organizations

Dry Tortugas National Park

Almost 70 miles (112.9 km) west of Key West lies a cluster of seven islands, composed of coral reefs and sand, called the Dry Tortugas. Along with the surrounding shoals and waters, they make up Dry Tortugas National Park. The area is known for its famous bird and marine life, its legends of pirates and sunken gold, and its military past.

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