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The C-4 Project: Channeling and Storing Water to Prevent Flooding
Miami-Dade County, FL - Hurricane Irene (1999) slammed into Miami-Dade County, causing heavy flooding, even in areas that had not been prone to inundation in the past. This was repeated a year later by Tropical Storm Leslie. Local emergency management officials decided that mitigation was necessary to minimize or eliminate the threat of repeated lowland and street flooding.
The Miami-Dade Flood Control Project, or C-4 Basin Project, was created to address the county’s extensive flooding problem. The project built on the existing canal system, and its goal was to relocate excess water from one area to another so it could be absorbed into the groundwater or held in reserve.
South Florida is home to the Everglades, and the land is predominately flat. As the area was developed and wetlands were drained, flooding occurred when excess water could not be absorbed into the ground or flow naturally away from an area hit with heavy rains. To handle the distribution of water, the entire region is crisscrossed by a 620-mile series of canals and waterways designed and overseen by the South Florida Water Management District.
Work began on the C-4 Project in 2000. At the heart of the C-4 basin is the Tamiami Canal, which begins in the Everglades National Park and traverses the Miccosukee Indian reservation, the critical Pensuco Wetlands, and several municipalities before flowing into the environmentally-sensitive Biscayne Bay.
The driving force of the C-4 Project is the forward pump station at the mouth of the Tamiami Canal, which is designed to push water flow downstream against the tide. A second station, at the mouth of the Miami River Canal in the C-6 basin, was built to offset the flow from the C-4 canal and prevent flooding upriver. There are three pumps in each station that can process approximately 4,500 gallons of water per second. One pump operating at that speed could fill an average swimming pool in three seconds.
For occasions when the canals cannot handle the water volume necessary to prevent flooding, an emergency detention basin, comprised of two reservoirs, was created to receive and store the excess water. In addition, a separate supply canal was built to divert excess water from the C-4 canal to and from the detention basin. This allows water to be shifted from area to area, not only in times of heavy rainfall or potential flooding, but also during instances when a need for water in other areas arises, such as when droughts occur. To help retain water in the detention basin, a catch canal was built adjacent to the detention area to capture water seeping from the basin and return it back to the reservoirs.
In South Florida, the water table is a few feet below the surface of the ground. Oolitic limestone, a porous rock, comprises the substrata. This limestone absorbs water easily, much like a sponge, and allows it to flow quickly underground. While water is flowing normally on the surface, it is also flowing laterally below the surface. When the ground is dry, the canals are kept at groundwater level, recharging the aquifer. During times of heavy rainfall, the water level in the canals can be lowered, allowing more water to flow through the ground and into the canal to prevent flooding.
When the Tamiami Canal was first constructed, a simple scoop system was used to dig the canal. The scoop pulled the dirt from the bottom and up the sides of the canal. This produced small ridges or ripples on the canal bed. Eddies would form in the water as it passed over these ridges, slowing the speed of the water flow down the canal. This slowing reduced the overall effectiveness of the pumps, preventing them from operating at the intended maximum capacity. To mitigate this problem while the C-4 Project was underway, the bottom and sides of the canal were smoothed and reshaped, allowing the water to move through the canal at a higher volume and speed. In addition, existing tertiary and secondary drainage systems were cleaned out, reshaped, and, in some cases, connected with the Tamiami Canal to channel water more effectively.
Flooding had also occurred numerous times at the Miccosukee reservation, located upstream of the C-4 upgrades. As part of the flood mitigation project, two portable trailer-mounted pumps were purchased that can be used around the reservation to mitigate localized flooding as needed.
The cost of the project totaled $70 million. The State of Florida was awarded $52.5 million from FEMA’s Hazard Mitigation Grant Program (HMGP). Following a major disaster declaration, the HMGP funds up to 75 percent of the eligible costs of a project that will reduce or eliminate damages from future natural hazard events. The Quality Neighborhood Improvement Program, along with the South Florida Water Management District and Miami-Dade County, contributed funds to for the remaining 25 percent.
The success of the C-4 project in reducing serious flooding has meant fewer insurance claims, reduced repair costs, and fewer wages lost to time away from work. More important, however, is what the project has meant to public safety. Neighborhoods and schools in one particular area are serviced by a fire station directly on the other side of the Florida Turnpike. During flooding, the underpass connecting the two areas became impassable. According to Frank Reddish, Emergency Management Coordinator for Miami-Dade County, “We had to find a way to divert the fire trucks, ambulances, or rescue trucks around the flooding. It went from a three-minute response time to a 15-minute response time. That’s a huge difference, especially if you’re [having a medical emergency or your house is on fire].”
Mr. Reddish summarized the impact of the flood mitigation project: “The success of a project is realized when you use it, and it works. The first time we turned on the pumps was due to heavy rainfall in the C-4 basin in December of 2001, and it didn’t flood. This year, when Hurricane Katrina went right over the top of the county, we had tremendous rainfall, and again we had no flooding.”
There are plans to construct a similar flood control system in the C-7 basin. “Now we’re encouraged,” Mr. Reddish said. “The fact that we did it, and it seems to have worked [in the C-4 basin] suggests that this could work throughout the entire Miami-Dade area. That would be the long term goal.”
Geographical Area: Single County in a State
FEMA Region: FEMA Region IV
County: Miami-Dade County
Activity/Project Start Date
Activity/Project End Date
Key Activity/Project Information
Hazard Type: Flooding, Hurricane/Tropical Storm
Activity/Project Type: Flood Control, Retrofitting, Non-structural
Funding Source: Hazard Mitigation Grant Program (HMGP), Local Sources
Funding Recipient: Local Government
Activity/Project Economic Analysis
Activity/Project Cost Amount: $70,000,000.00
Activity/Project Disaster Information
Since mitigation effort began, has a disaster tested its value? Yes
Flood Control, Retrofitting, Non-structural
Hazard Mitigation Grant Program (HMGP), Local Sources
Flooding, Hurricane/Tropical Storm