Monroe County Takes Steps to Address Sea Level Rise on Road Projects

Monroe County’s new road projects will address sea level rise to help prevent tidal flooding, like this case on Adams Drive in Key Largo in 2015. Photo by Stephanie Russo.

Monroe County took several steps Wednesday to create a framework for dealing with County roads that need to be adapted to sea-level rise. This continues the small County’s leadership in addressing climate change adaptation at the local level.

At its January monthly meeting, the Monroe County Board of County Commissioners first adopted the final report of the “Monroe County Tidal Flooding Pilot Roads Project” for the Twin Lakes community in Key Largo and the Sands community on Big Pine Key. The BOCC also approved moving forward with the design phase of road elevation and drainage projects in those two neighborhoods, implementing the report’s recommendations to help prevent tidal flooding.

This paved the way for the BOCC to approve a resolution that sets an interim standard for determining the elevation of future County road improvement projects to account for future sea level rise. The Commission also directed the start of an analysis of all 300 miles of County roads to identify those that are at the greatest risk level of tidal flooding.

“Few cities or counties around the United States are as advanced in sea level rise planning and implementation as we are in Monroe,” Monroe County Sustainability Director Rhonda Haag said. “This is despite the extra difficulty we have to deal with this issue due to our island-chain geography, low elevation of all roads and porous rock base.”

Monroe County’s GreenKeys! Sustainability Action Plan estimated that 144 miles of County roads could be subject to nuisance flooding by 2030 under the Southeast Florida Climate Change Compact’s “low” sea level rise projections of 3-7 inches and that 188 miles of roads may be exposed under the “high” sea level rise scenario of 9 to 24 inches.

The countywide road analysis will include updated Lidar data to better provide road elevation information. Current elevation data available to the state was collected by aerial methods in 2008 and can be off by up to 6 inches for road elevations in Monroe County. The new data will be obtained by more accurate ground methods.

Because this new countywide analysis may take 18 months to complete and the County needs to plan for elevation of roads now in the project pipeline, the request for the interim standard was necessary.

Monroe County decided to move forward with the pilot projects following the 2015 King Tides that led to flooding of more than 3 weeks in several neighborhoods in unincorporated areas of the County. King Tides occur annually in the fall, when the moon, sun and Earth are aligned to create gravitational forces that produce the greatest tidal fluctuations.

The Twin Lakes community (Shaw Drive, Crane Street and Adams Drive) and the Sands community (Father Tony Way and the Avenues) were chosen because the impacts of those King Tides were among the highest.

For Twin Lakes, the report recommended raising portions of the community’s roads 5 inches at a conceptual cost of $920,000. For the Sands, the report recommended raising portions of the roads by 11 inches at a conceptual cost of $2.63 million.

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