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Sea-Level Rise Resiliency Committee continues to gather input for Captiva panel

By Staff | Aug 13, 2019

PHOTO PROVIDED Using its Sea Level Rise Viewer, the NOAA's mapped prediction for the inundation of Captiva as of 2050 based on its Intermediate High Scenario (1.9-foot rise in sea level).

As coastal communities throughout Florida are trying to identify and address the impacts of climate change, particularly in relation to rising sea levels, an island group is working to do the same.

Earlier this year, the Captiva Community Panel moved forward on creating the Sea-Level Rise Resiliency Committee, with the aim of looking at if Captiva needs to develop a future plan to fortify the island against the rising waters. Comprised of residents and panel liaisons, and guided by a hired consultant, it has been collecting information and data and putting it all in a report for the CCP.

According to a version of the living document provided at last month’s panel meeting, the mission of the group is to “gather information on the effects of sea-level rise’s impact on Captiva Island, including defining assets, consulting experts, defining areas of vulnerabilities and provide alternative approaches to the Captiva Community Panel for resiliency and adaptation.”

The report notes that the planning horizon is 30 years, with five-year increments.

“This committee selected a 30-year planning horizon as the initial project scope, with a projected sea-level rise of 1.9 feet, consistent with NOAA intermediate high projections,” it states. “At 1.9 feet, there are areas of Captiva, particularly along the fringe of the bayside, which will be underwater or flooded frequently.”

The group notes that using the NOAA’s tools, the risk scenarios for sea level rise related to Captiva over the 30 years “range from very optimistic (.89 feet) to very pessimistic (2.89 feet).” It also points out that the NOAA uses a “bathtub model,” which is based on sea level rise and does not include the impact of flooding from storms.

In terms of the island’s assets – based on importance to recovery after an incident – the group identified: roads and bridges, electrical and power, water, and the three package plants and FGUA’s treatment plant as Priority 1; Captiva Civic Center, fire station, helicopter ports, Village drainage system and beach dunes as Priority 2; and Island Store and Village Center, homes, parking lots (for staging for recover), marinas, Captiva Memorial Library, Captiva Chapel by the Sea, cemetery and archeological sites as Priority 3, according to the document.

On the subject of storminess and building codes, the committee reported that the “big lesson from all storms is buildings that are elevated, set back from the Gulf and built to higher standards do best in storms and limit recovery.” It noted that property owners with homes built before the 2002 adoption of the Florida Building Code should consider what they can do to strengthen their buildings, and “that well-pruned native vegetation does best” in a storm.

According to the report, the group’s consultant determined through research that it appears unlikely Captiva ever would be over washed in a hurricane. It continues that because the island is relatively high with a great deal of vegetation, there will be overwash of low-lying areas. Beach restoration is cited as a large portion of that assurance as a “healthy, wide beach is great protection during storm events.”

“Captiva may want to consider in the future bulking up the dunes to help prevent overwash,” the committee notes. “Beach vegetation, like mangroves, can help protect the shoreline.”

The report also covers potential mediations, including mangroves and dunes.

“Mangrove trees provide significant wind mitigation during hurricanes by absorbing, deflecting and otherwise decreasing wind speeds. Mangroves are thought to do the same during catastrophic storm surges, that is, absorbing, slowing down and deflecting water,” the group reports. “Mangroves grow higher with rising tides and keep up with sea level rise projections because they build land (accrete) through deposition of leaves, algae, sea grass, sediment and pollutants.”

In terms of mangroves, some possible actions identified were: bayside mapping to determine existing seawalls and the most beneficial planting locations; sediment nourishment along the bayside to create additional habitats for mangroves, then an active mangrove planting program; and education campaign for homeowners.

As for dunes, the consulting engineer for the Captiva Erosion Prevention District’s indicated that the island might want to consider adding sand to the dunes during future beach restoration projects.

According to the report, other potential mediations the committee intends to research are oyster beds, sea walls, revetments and riprap, storm water management systems, and building regulations.

An updated version of the document was expected to be provided at the panel meeting today, Aug. 13.