Facing Sea Level Rise, Miami Beach Uses GIS to Prioritize Mitigation Projects
Miami Beach, Florida, which lies on a barrier island a few miles off the coast of Miami, is one of the most vulnerable areas for sea level rise in the United States, if not the world.
By the end of the century, global mean sea levels could rise by about 11 to 43 inches, according to the United Nations Intergovernmental Panel on Climate Change (IPCC). South Florida is likely to face 17 to 31 inches of sea level rise by 2060, according to projections made at the 2019 Southeast Florida Regional Climate Leadership Summit. And Miami Beach has a unique, bowl-like geography wherein the center of the island is lower than its beaches to the east and coastal defenses to the west, making it even more prone to flooding.
That's why the city has been working with Jacobs, a technical consulting engineering firm, to find out where its biggest flooding concerns are and determine how to consolidate public works projects to better prepare for sea level rise while minimizing disruptions to residents. Using ArcGIS Pro and ArcGIS Spatial Analyst, the team at Jacobs combined climate change projections with the city's infrastructural data—and now, Miami Beach is tackling these projects efficiently and effectively.
Flood Management That Works—But There's More to Do
The City of Miami Beach already experiences unusual flooding. Higher-than-normal tides, called king tides, now flood the streets regularly.
"Parts of Miami Beach experience sunny-day flooding several times a year—especially in the fall—and these events are becoming noticeably more frequent," said Laurens van der Tak, water resilience director for the Americas at Jacobs.
"Adding significant rain events to those high tides causes substantial flooding in the lowest-lying areas of the city," added Roy Coley, director of Miami-Dade County's Water and Sewer Department and former director of the Public Works Department at the City of Miami Beach.
The city began mitigating tidal flooding back in 2013. It implemented a cutting-edge stormwater management plan that considered 30-year forecasts for sea level rise. Miami Beach started elevating its most vulnerable roads and improving its stormwater pumping system.
"We were one of the first cities to actually take bold steps to manage flooding," said Coley.
But predictions have changed since then, and by 2017, the city's new mayor, Dan Gelber, wanted to ensure that Miami Beach was on track to minimize the effects of sea level rise. Working with the Rockefeller Foundation, the city brought in the Urban Land Institute (ULI) to review the projects and plans it already had underway.
The organization did a comprehensive analysis and concluded that, overall, the city had done many things well. However, there was still room for improvement—especially when it came to implementing blue and green infrastructure (a way of using urban green spaces to manage floodwater) and ensuring that each project provided multiple benefits to the surrounding neighborhoods.
To put ULI's recommendations into action, the City of Miami Beach enlisted Jacobs. The team—consisting of van der Tak; Jason Bird, the company's Florida resilience lead; hydrologists; planners; and a robust group of GIS experts and spatial analysts—used GIS to visualize all the data.
"GIS has been an invaluable tool for mapping out areas that are at high risk of flooding and prioritizing flood mitigation projects spatially," said van der Tak.
Taking on Sea Level Rise While Minimizing Disruptions
Using ArcGIS Pro and the Spatial Analyst extension, the team at Jacobs mapped out Miami Beach's infrastructural priorities and determined ways to improve how the city is preparing for sea level rise.
The City of Miami Beach provided extensive amounts of data from its asset and capital management program, which Jacobs combined with its data on flood risk and city service needs. The project had three aims:
- Determine how Miami Beach can better incorporate blue and green infrastructure to mimic nature's water cycles and reduce flood risk. This includes developing ways to preserve the island's freshwater layer (lens), which keeps salty groundwater at bay, to protect trees and infrastructure and support public services and facilities.
- Evaluate the city's road-raising strategy and ensure that it meets Miami Beach's evolving needs.
- Examine project size and sequencing so the city can prioritize projects and see if any are too large (and thus take too long) or too small (and don't provide adequate benefits).
"The city has done a great job identifying tidal flood risk areas that require immediate intervention," said Bird. "We've been able to add layers to previous analysis to capture other city needs, such as water, wastewater, and stormwater management and road enhancement projects. By spatially analyzing all those different critical city functions and understanding how they interact with one another, we've been able to review city projects and ensure that when a capital project is performed, we can minimize disruptions in the neighborhood."
Projects Get Prioritized and Consolidated
After approving Jacobs's recommended flood adaptation guidance in October 2020, the City of Miami Beach was set to start implementation—beginning with consolidating road-raising and infrastructure improvement projects in certain high-priority neighborhoods.
"We are now able to look at other city infrastructure projects—such as water and sewer upgrades or multimodal transportation—and, using GIS, package and sequence those projects spatially to minimize construction-related community disruptions," said van der Tak. "In bundling all planned capital improvement projects in a given area like this, it also saves on costs for any belowground utility work."
One area that Jacobs focused on was helping the City of Miami Beach preserve its freshwater lens.
"As sea levels rise and saltwater pushes up, there's a layer [lens] of freshwater between the surface of the land and the saltwater," explained Coley. "If we lose that, our vegetation will go away. But by using blue and green infrastructure, we can constantly replenish that freshwater lens and abate the sea level that's rising beneath us."
"That freshwater lens, which sits on top of the saltier groundwater below, is important for a number of reasons, like minimizing salt corrosion of foundations and sustaining trees and other vegetation that not only help capture rainwater but also provide shade," added van der Tak. "These are novel ways to manage flooding rather than treating it as stormwater runoff."
The City of Miami Beach is converting what was initially a liability into something useful. Being able to group blue and green infrastructure projects with road-raising and stormwater system improvement plans in areas with the most pressing needs will make this work more efficiently and effectively than ever.