EAA Conveyance Improvement Project aims to reduce post-storm flooding

Last August, Tropical Storm Isaac dumped record amounts of rain on parts of Florida as it made its way from the Caribbean to Louisiana. - NASA photo

Last August, Tropical Storm Isaac dumped record amounts of rain on parts of Florida as it made its way from the Caribbean to Louisiana. Even before Isaac’s arrival, an upper-level low had spawned numerous showers and thundershowers over southeastern Florida. The combination of the two resulted in totals of as much as 18 to 20 inches in central Palm Beach County. Meteorologists called it a 1-in-100-year storm.

Canals designed to handle irrigation and flood control overflowed, causing extensive damage to farm fields. Water coursing through the South Florida Water Management District’s primary canal in Palm Beach County – known as C-51, reached a record 10,300 cubic feet per second. Water-control gates remained open and pump stations operated at maximum capacity for days.

During and after the storm, the district moved about 105 billion gallons of water away from residents in Palm Beach, Broward and Miami-Dade counties, according to a district report. Although many neighborhoods had excess water in swales, ponds, roadways and back yards, fewer than 50 homes were reported to be directly impacted by flooding. Rural areas with local drainage systems unable to handle the historic quantities of rainfall saw the most flooding and had the longest recovery times.

In the following months, the district’s engineers laid out a $150 million proposal to improve water flow through the Everglades Agricultural Area to increase flexibility of the flood-control system and improve flood protection for farms. It’s called the EAA Conveyance Improvement Project.

The project is expected to allow water flows to be redistributed within the Everglades Agricultural Area, reduce pumping of water back into Lake Okeechobee, increase flood protection for agricultural areas by widening canals, improving levees, and improve water quality.

However, the project faces funding challenges, operational constraints during construction, environmental impacts and the complications of working with multiple landowners.

Manageable pieces

The district met with agricultural interests on April 2. Among items discussed were how to break the large project up into manageable pieces that would still achieve project goals. The group discussed making improvements to the Cross (L16) canal, also known as the Bolles Canal, the first priority. The consensus was that that canal has the most existing problems with supplying irrigation water and providing storm drainage.

The stakeholders also identified the Duda Road crossing as a major conveyance problem and agreed that a new crossing needs to be built west of the existing one before removing the existing crossing. In addition, concerns were addressed about the existing connections of the Cross and Ocean Canals to the Hillsboro Canal. The original design for that part of the canal system was for flows to be returned to Lake Okeechobee. The group agreed these connections should be reviewed and improved to enable flows to be instead directed to existing Stormwater Treatment Areas. Several in attendance raised concerns about drainage problems in the Ocean Canal, which overflowed during Tropical Storm Isaac, flooding fields.

The concensus from the stakeholder meeting was that three priorities must be tackled first to see potential quick benefits. Those include replacement of the Duda Road culvert crossing with a bridge, removal or enlargement of culvert connections from Cross and Ocean Canals to the Hillsboro Canal, and repair or raising of the Ocean Canal levee section east of G-341.

“Due to their shallow depths, the Bolles and Cross canals have never had adequate capacity to move water off of and away from the area farms during heavy rainfall events; this is something the district has been aware of for many years,” said Kerry Kates, FFVA’s director of water and natural resources, who attended the meeting.

“It has been documented in CERP studies prepared for SFWMD that increasing the capacity of this canal system would drastically improve the district’s operational flexibility when it comes to moving water between the interconnected basins within the EAA and that it would greatly alleviate the flooding issue that so many of the growers have had to contend with over the last several decades,” he added.

Kates said that during the meeting, district staff were somewhat surprised at the willingness of the landowners to do to whatever is necessary, including granting construction easements along the banks of the canals, to expedite the process of permanently remedying the flooding issue.

“The speed at which the growers were able to come together and reach a consensus on which shortcomings of the existing drainage system should be addressed first should clearly communicate to the district that they are more than willing to cooperate. I think now it’s a matter of keeping pressure on SFWMD to ensure we maintain forward momentum,” he said.

A summary of the April 2 meeting is available here.

 

 Historic Magnitudes of Water

Water Moved to Tide and Storage Areas

105 billion gallons
Water Moved by Emergency Pumps 2.3 billion gallons
72-Hour Rainfall Maximum 14.85 inches
C-51 Canal’s Record Flow Rate 10,300 cubic feet per second
Water Moved to L-8 Reservoir 3.1 billion gallons

 

Comments are closed.