Hurricanes, sea level rise and creating sustainable communities

02/09/10 Matthew Cimitile
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As a peninsula surrounded by water and prone to extreme storms, Florida is one of the states with the most to lose if sea levels rise to the degree experts predict. With 4500 square miles of land below 5 feet of sea level, any rise in levels will submerge coastal land while increasing the risk of flooding to populations, according to the EPA. Tim Frazer is a coastal hazard specialist at the University of Idaho who presented results on Sarasota County’s coastal exposure.

“We started this work with this goal in mind; we wanted to develop this framework that we could integrate science with local stakeholder knowledge, community knowledge. And there was this call out in the community for work that can provide ammunition for local decision makers on some of the kind of issues and problems that were going on and would continue to go on in relation to climate change and daily issues related to sustainability. So people were having to make decisions but they weren't really comfortable with the kind of scientific information or the kind of tools that they had to make those decisions. So our goal was to kind of integrate science with stakeholder input and also with that we wanted to enhance community resilience to whatever hazard might be coming down the pike.”

Sea level is predicted to rise anywhere from ½ to 2 feet by the end of the century, according to the U.N. Intergovernmental Panel on Climate Change. Other experts believe this number is too conservative and seas could rise by at least one meter or three feet by 2100, based on the most recent analysis of glacier melting in the arctic regions. Frazer and researchers at Penn State University and the U.S. Geological Survey took these seal level rise estimates and plugged them into a “surge from hurricane model” to project the degree to which population and businesses would be impacted under various hurricane conditions.

What they found was that if sea levels rise by 1 and ½ to 2 feet by century’s end, a category 3 hurricane would create similar surge conditions and flooding that a category 5 would produce in the county today.

“When you get to 120 on a category 3 storm it is starting to look like a category 5. What we noticed is where are areas that wouldn’t be flooded today that might be flooded in the future and what are in those areas. Those are the kind of places we were predominately concerned about looking at. So what does the county have in these areas, do they have water treatment facilities, hurricane evacuation shelters, do they have sufficient road work because normally if you look at these darker colors you may not move those people, you may not have to move those people but in the future you might. If you have to move them in the future do you have adequate transportation resources in place to make that happen and do you have a place to put them.”

On the map in dark red colors indicating flooding were cities like Venice, Osprey, and South Sarasota. Those cities and population centers farther to the east were in the new surge zone created by a category 3 with higher sea levels.

After collecting and analyzing the data from these models, the researchers put together focus groups consisting of people from the environmental, business, planning, infrastructure and government community to discuss and develop solutions to create more sustainable coastal areas.

“In our conclusion the big thing that jumped out to us was that urban surface boundaries in coastal communities do a lot to contribute to hurricane hazard exposures. Possible adjustments that came out of this that was talked about was to relax or massage the urban surface boundary, steer development to a certain degree outside the hazard zone, relocate and replace infrastructure when possible and to explore some evacuation alternatives. ”

Specifically, the focus groups suggested relocating businesses that were not beach specific and high density residential communities outside hazard areas, to replenish wetlands, develop land swaps and add or expand on more north to south transportation corridors like I-75.

The researchers plan to continue looking at Sarasota County by using lidar technology, where an aircraft sends laser pulses to the land and back to precisely map the topography of the land below and provide community planners more specific data on coastal features and land use. They also are working with other counties in Florida on similar coastal hazardous area projects.

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