Case Study

Coastal Resilience In Monroe County, Florida, USA

Case Study Summary To enhance the resilience of its low- lying infrastructure to frequent flooding from sea level rise and storm surge, Monroe County instituted a pilot project in two communities, which involve elevating approximately 6,400 feet of specified roads and installing 2,000 feet of pre-treated and pressurised closed stormwater management systems.
Sector
           Water
           Transport
Key Topics
  • Coastal resilience
  • Property protection
Project Owner Monroe County
Project Start/Completion May 2019 – Ongoing
Location Key Largo and Big Pine Key, Monroe County, Florida
Community Impacted Coastal
Vulnerable Groups Impacted Women and girls, youth, elderly people
Climate Hazards Mitigated Flooding, Hurricanes/cyclones
Case Study Provided by WSP Logo

To enhance the resilience of its low- lying infrastructure to frequent flooding from sea level rise and storm surge, Monroe County instituted a pilot project in two communities, which involve elevating approximately 6,400 feet of specified roads and installing 2,000 feet of pre-treated and pressurised closed stormwater management systems.

About the Project

 Projections from the Southeast Florida Regional Climate Change Compact indicate that areas of the Florida Keys may experience sea level rise of 12 inches by 2030, and more than 30 inches by 2060. To communities that populate these islands, that level of increase poses a significant threat of inundation.

To enhance the resilience of its infrastructure, Monroe County instituted a pilot project in two communities— Twin Lakes in Key Largo and the Big Pine Key community of Sands—where streets are bordered by wetlands and canals, and are already subject to frequent flooding during king tides and intense storms, and precipitation events.

As a partner to the county, WSP performed a pilot study to assess the 20-year tidal record and 2015 event and determine a target elevation for roadways and required drainage improvements to adapt to the new conditions. The study outcomes informed the project solution, which includes elevating approximately 6,400 feet of specified roads and installing 2,000 feet of pre-treated and pressurised closed stormwater management systems.

The drainage design consists of a gravity collection system with a pump station discharging into multiple injection wells. All runoff will be routed to the pump stations, one for the Key largo Project and the other for Big Pine Key, using trunk lines along the main roads. The system includes numerous inlets and manholes, above ground electrical pump station control and distribution panel and components, generator, underground valve box, wet well, pollution treatment unit structure and a solids storage sump. The design storms for this system are the 10-year Soil Conservation Service (SCS) Type II storms with durations of 24 and 72 hours correspondingly, and proposed improvements take into consideration the Sea Level Rise projections for year 2050.

Additionally, the project involves reconstructing and resurfacing the pavement, signing and marking, and conducting property surveys to harmonise the elevated roads with adjacent properties. A retaining wall has also been proposed along the road, to provide safety for drivers and surge protection.

The roadway and drainage design required close coordination with the Florida Keys Aqueduct Authority’s water mains and vacuum sewer lines. The design adheres to Monroe County’s adopted methodology for adapting infrastructure for sea level rise.

Intended Outcomes

 This project is designed to protect a major access road to a low-lying, low-income subdivision that is subject to frequent and persistent flooding due to storms, tides, and sea-level rise. It will maintain access to 190 homes in a low-income residential neighborhood of which 115 homes sustained substantial damage due to Hurricane Irma, and it will help to sustain property value.

Number of vulnerable people made more resilience by this project

~4,000

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