TAMPA — Rising sea levels could swell Tampa Bay 5 to 19 inches over the next quarter-century, sending more water to lap at the edges of the city of Tampa.
That's one conclusion of a new analysis from the Hillsborough City-County Planning Commission, which looked at how potential sea-level rise could affect Tampa and its most flood-prone areas through the year 2040.
"This is actually one of the biggest challenges, if not the biggest challenge, that this region has," says Tampa City Council member Harry Cohen, whose low-lying South Tampa district already is checkered with flood-prone neighborhoods. He ticks off the challenges affected by rising water: transportation, infrastructure, development, having clean drinking water.
"All these things are inter-related," he says. "Our economic future is dependent on us being dry and us not being so threatened by flooding that people can't live, work and play."
Other local governments around the bay are doing similar work.
In 2015, Pinellas and Pasco county governments had representatives on a Tampa Bay-wide Climate Science Advisory Panel that concluded the region's nearly 700 miles of shoreline could see sea levels rise between 6 inches and 2.5 feet in 2050 and from 1 to 7 feet in 2100.
That projection was built on work done by the National Oceanic and Atmospheric Administration as well as local data about how the level of the bay has changed in recent decades. The Tampa study is based on that projection, though with a more local focus.
Pinellas County and St. Petersburg also are teaming up on a $600,000 project to do a county-wide vulnerability assessment of critical infrastructure that's expected to guide changes to county policies. Half the money will come from a federal grant to the county. The other half is coming from St. Petersburg's settlement with BP over damages caused by the Deepwater Horizon oil spill.
St. Petersburg officials also think they were the first city in Florida to update their comprehensive land-use plan to comply with the state's "peril of flood" act, a 2015 law requiring local governments to plan for floods and impacts from sea-level rise. Public works and water resources officials already are factoring the projections into plans to upgrade infrastructure and are looking at potential updates to codes and policies.
In Clearwater, the City Council on Thursday night approved using a $20,000 state grant to hire a consultant to help update the city's comprehensive plan and develop engineering approaches to reducing flood risk in coastal areas to comply with the peril of flood act.
Along with St. Augustine and Escambia County, Clearwater is one of three local governments statewide chosen by the state Department of Economic Opportunity for a project to assess vulnerabilities to projected increases in coastal flooding and develop strategies to deal with them.
In Tampa, a rise of 5 inches in the bay could affect an estimated 864 residential properties — though, officials note, not necessarily all or even most of every property affected — as well as about 50 commercial properties. Some government-owned property, including Stewart Middle School, which overlooks the Hillsborough River north of downtown, could see minimal impacts.
At the high end of the projections, more than a thousand residential properties could be affected. In all, more than 15,000 people live in the areas expected to see rising tides. Those are mostly along:
• Coastal areas north of West Shore and the Howard Frankland Bridge around to the Courtney Campbell Causeway.
• The banks of the Hillsborough River upstream from Blake High School.
• The rim of McKay Bay generally east of Palmetto Beach and around the mouth of the Palm River.
• Port Tampa City on the west side of the South Tampa peninsula, south of Gandy Boulevard and next to MacDill Air Force Base.
In a worst-case scenario, the report said, affected areas could include Tampa General Hospital and 30 city parks — among them, the $35 million Julian B. Lane Riverfront Park, Curtis Hixon Waterfront Park and other parks along the Riverwalk.
The planning commission's analysis did not tease out the implications for MacDill, but others have. Last summer, the Union of Concerned Scientists projected that sea levels at MacDill would rise up to 1.7 feet by 2050 and up to 6.2 feet by 2100. That would cover wetlands at the base, but little developed land. MacDill officials expect a "minimal impact" by 2050 on the base's commands and flight operations.
All of the areas in question are relatively small when compared to the city as a whole. In the most extreme case, the parcels that would somehow be affected cover a total of more than 13,000 acres, but only 777 of those acres actually would be expected to see an impact. And that's in a city that covers 113 square miles.
What's more, nearly fourth-fifths of the acreage expected to be affected is publicly owned, while less than a 6 percent is residential.
"At least in this time frame of 2040, the potential impact at the high end of the impact is really small," said Randy Goers, Tampa's urban planning coordinator.
Still, the city is looking at updating its comprehensive plan with policies to, for example, flood-proof pumping stations and electrical facilities in vulnerable areas; line waste water pipes to reduce inflow through cracks that could overwhelm the sewer system; and look at the need for new pumping stations in vulnerable areas.
The good thing, Cohen says, is that neither the city's main water treatment plant nor its wastewater treatment plant are in the areas affected by the projected sea level rise through 2040.
A lot of the fixes that are needed in the most affected area could be addressed through Tampa's new 30-year, $251 million stormwater program, especially in the area south of Euclid Avenue to MacDill Air Force Base, he said. But Cohen also would like to see the planning commission, when it considers proposed land use changes in Tampa, factor stormwater impacts into its recommendations to the city.
As sea levels rise and flooding spreads, Florida communities will have to look at building codes, the elevation of streets, the height of sea walls, the use of pumps and the installation of flow-control valves to keep rising tides out of the stormwater drainage system, said Stephen Tilbrook, an environmental and land use lawyer in the Fort Lauderdale office of the GrayRobinson law firm.
"The moral of the story is that as sea levels rise (and) as communities evaluate the impact of rising sea levels ... we may have to adjust the way we do land development and the way we plan for the future," he said.
Contact Richard Danielson at email@example.com or (813) 226-3403. Follow @Danielson_Times.