Completed coastal vulnerability study presented to council
The Sanibel City Council recently heard a presentation and received the final report on a coastal resiliency study of the islands, conducted in partnership with Florida Gulf Coast University.
Dr. Michael Savarese, a professor of marine science and environmental studies with FGCU’s Department of Marine and Ecological Sciences, provided an overview of the “An Assessment of Coastal Vulnerability Due to Sea-level Rise and Increased Storminess” at the Oct. 2 meeting.
The six-month project, which concluded in June and was funded through the Florida Department of Environmental Protection’s Florida Resilient Coastline Programs, aims to help Sanibel and Captiva understand their vulnerabilities to sea-level rise and storminess, plus identify the most relevant effects for them.
“We employed a community-engaged approach,” Savarese said of conducting the study.
“This is just a first step,” he added. “There are many other steps to follow.”
In his presentation, Savarese explained that climate change vulnerability is predicting or anticipating future effects across the landscape and protecting community assets. It is key to preserving or improving quality of life and economic vitality and to maintain urban, cultural and natural resources.
Distinguishing vulnerability, adaption – resilience – and mitigation are needed for preparedness.
He noted that with the planet’s warming comes warmer oceans, hence greater storminess.
According to Savarese, the most recent sea level rise predictions from the National Oceanic and Atmospheric Administration are 2 to 2.5 meters in a worst-case scenario or as modest as a half-meter.
Community engagement and documenting the history of coastal habitat change since 1970 were two aspects of the study. Engagement entailed focusing the attention of civic leaders and island residents on the problem and prioritizing the critical natural, cultural and urban assets of the islands “under risk.”
As for documenting the habitat change, it involved determining impacts in recent years.
Digital elevation models for 1998, 2004 post-Charley, 2004 post-Ivan, 2006, 2010 and 2015 were generated. The coastal landscape from 1970 to 2015 were characterized using the DEP’s beach profiles and digital elevation models, and sediment budgets were calculated through the same time interval.
The seaward-most vegetation line was tracked and coastal vulnerability maps were generated.
“All of the steps support the next step, which is computer-generated modeling,” he said.
Sanibel and Captiva were divided into sectors – seven and three, respectively.
“That can help you better understand your vulnerability,” Savarese said, explaining that digital elevation models can be used to identify erosion hot spots or stable areas related to the strandplain.
For example, sectors 3 and 4 bookending Blind Pass showed “significant sediment loss.”
He continued that sectors 3, 4 and 7 exhibit shoreline recession and erosion, making them the most vulnerable. The remaining sections of Captiva – sectors 1 and 2 – contain strandplains that are narrower than those on Sanibel but appear to be reasonably resilient. Left on Sanibel, sectors 5, 6 and 8-10 were founded on strandplains and experienced significant progradation, making them the most resilient.
“Your outer coast is relatively fortunate,” Savarese said.
As for the community engagement portion of the study, eight teams were formed: community infrastructure, business community, development community, school and education, social resources, natural and cultural resources, Captiva Community Panel, and community at-large. With six to eight members on each one, the goal was to express concerns and identify, map and prioritize assets.
He noted that they recorded more than 100 assets, plus extra ones came from the city.
“This was a great effort,” Savarese said, noting that there were over 500 total.
The teams vocalized some common concerns, such as improving awareness and engagement with residents, developing resources to inform about the environmental risks of barrier island life without instilling fear or hopelessness, and engaging the living and working communities in preparedness.
“To be truthful, to be transparent, but not to exaggerate the potential for harm,” he said.
With the study’s completion, the following next steps are recommended:
– Forum/discussion series designed and implemented for the public.
– Develop resources to inform businesses, real estate investments and tourism efforts on risks.
– Concerted effort to minimize “down time” after a major event; develop a “post-event resiliency plan.”
– Show greater consideration for the service sector employees who may suffer disproportionately.
– Remain proactive on the use of green infrastructure to improve resilience.
– Gulf-side is reasonably resilient, at least with respect to disturbances to-date; coastal vulnerability should still be investigated in anticipation of more powerful storms exacerbated by sea-level rise.
– There are erosional hotspots (sectors 3, 4 and 7) that require attention and adaptation planning.
– Sanibel-Captiva is perhaps more vulnerable to storm surge and sea-level rise on the backside.
“We recommend pursuing a storm and sea-level rise inundation modeling for the two islands,” Savarese said.
He noted that the FGCU staff is happy to stay involved.
“We’re there to help,” Savarese said.
Following the presentation, Sanibel Natural Resources Director James Evans spoke.
“We aren’t seeing anything new,” he said, pointing out that city staffers are aware of the critical hotspots, such as Blind Pass, identified within the study. “But a lot of new information.”
“I think there’s a lot of good information in the report,” Evans added.
He noted that a “modest” amount of funding is in the budget for modeling.
“So hopefully we can get some money to do that modeling,” he said.
“This is really our first step to developing an adaption plan on Sanibel and Captiva,” Evans added.