How climate change models help South Florida plan for the future

South Florida is – quite literally – getting into deep water as the climate changes. The region’s eight million inhabitants live in cities and towns that are, in some cases, just inches above sea level. As sea levels rise and storm surges push water ashore, the staff of the South Florida Water Management District will be among the first to deal with it.

Serving 16 counties from Orlando down to the end of the Florida Keys, the district manages flood control, water procurement, ecological protection and water quality. It does this work in conjunction with dozens of state, county and local governments and utilities. Every step of the way, an in-house team of engineers and scientists guide the district’s planning and operations.

Threatened by rising sea level, storms and saltwater intrusion

South Florida is at the end of a peninsula that is threatened by water on three sides, as well as from above and below. The skies inundate the region with more than 53 inches (134 cm) of rainfall per year, mostly between June and October. Hurricanes swirl through the Atlantic Ocean and Gulf of Mexico and crash into land.

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The district is also responsible for The Everglades, the largest freshwater wetland in the U.S., which is at risk from fertilizers, agricultural chemicals, urban runoff and seawater. Salt water in South Florida also creeps into the limestone bedrock to replace fresh water pumped out to supply an ever-growing population.

A three-tiered flood control system

The South Florida Water Management District (SFWMD) is one part of a three-tiered flood control system. This includes main flood control canals built by the U.S. government in the 1940s and 1950s, secondary canals operated by counties, cities and special drainage districts that feed the main canals, and finally tertiary systems that homeowner associations use to drain their neighborhoods. The system includes salinity barriers to prevent saltwater intrusion.

“We are not just one organization stepping up,” says Akintunde Owosina, chief of SFWMD’s Hydrology and Hydraulics Bureau, who oversees the district’s climate change modeling unit. “It requires many to affect something that is robust to mitigate sea level rise. There has to be tight integration to be able to come up with effective adaptation strategies.”

The Southeast Florida Regional Climate Change Compact was formed as a way to coordinate mitigation and adaptation activities across county lines.

Models to predict how systems will perform with sea level rise

As sea levels rise, it is important to predict how well systems will perform in the future. Part of the district’s cooperation with stakeholders upstream is sharing the results of its Flood Protection Level of Service program. This program is a deep assessment of the infrastructure that integrates information from current on-site inspections with detailed modeling of different future conditions, including sea level rise and weather scenarios.

“Modeling allows you to test something that you can’t test in the real world,” Owosina says. “You can evaluate what will happen in 50 or 60 years without waiting 50 or 60 years. You can experiment in dry-lab conditions, evaluating ‘flooding’ in an area without flooding anybody out. It allows you to make important decisions without incurring the actual costs of the issue.”

For years, the modeling experts at the district have reviewed the science and math around climate change and sea level rise. They have reviewed the climate models to determine their applicability in Florida, as well as papers and technical publications that describe contributors to sea level rise, such as melting ice in Greenland and Antarctica, oscillations in ocean temperatures, sunspots, and flash storms.

How the district is handling uncertainty

The district has also collaborated with colleagues in the region to grapple with the uncertainty that plagues modeling projections of sea level and other effects of climate change. Estimates of sea level rise range from half a meter (1.6 feet) to two meters (6.6 feet), which is not nearly specific enough to facilitate planning, Owosina notes.

“We backed away from making predictions,” he says. “Instead of using the models to predict sea level rise, we’ve turned the problem around to look at the infrastructure we’re responsible for and determine what level of sea level will render the infrastructure ineffective.”

“Then you can set aside the uncertainty and pick a trigger and say, ‘when I get to this certain amount of rise, the system starts to operate ineffectively,’” Owosina explains. “If it takes ten years to build new infrastructure, you set a threshold and say ‘just before I hit that level, I’ll begin building the new infrastructure.’ If the estimates are wrong, you’ll just get to the threshold faster, or later.”

Comparing costs and benefits of all cases

Modeling can help planners in the district or in associated municipalities understand the long-term benefits of different adaptation strategies. For instance, Owosina says, a city could enlarge its canals or add pumps to increase floodwater discharge capacity, a fix that could contain flooding and prevent washed-out roads for five or ten years. But raising the roads – while more expensive – could be a more efficient approach and a longer-term solution to keeping traffic on the move for decades to come.

“Things like that are what we can evaluate with models,” he says. “We can compare costs and benefits of all cases, and look at what can be most effective in 15 to 20 years, 50 years, or the lifespan of some of the assets, which can be 50 to 100 years.”

Working with local and international partners

The district’s modeling program starts with an evaluation of climate science, dives deep into planning, and resurfaces in a wide range of conversations with other local governments and districts. SFWMD works closely with counties and municipalities throughout South Florida, providing technical assistance and data. The district also seeks inspiration and insight from colleagues around the world, Owosina notes.

“We work very closely with the Dutch,” he says. “They have hundreds of years of experience working below sea level. And we work closely with local governments on grant funding and other projects.”

This local and international cooperation has delivered three key insights, Owosina says. “We need background information, we need to know the current state of the assets, and we need to plan for a resilient future.”

Download the full version of this article and other great stories at Mission: Water

By Steve Werblow

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