The Kissimmee River Restoration Project (KRRP) is one of the largest river restoration efforts ever undertaken globally. It was conceived to reverse decades of ecological damage caused by the government-mandated channelization of the river system. The project required applying sophisticated engineering methods to physically reconstruct the landscape and reestablish the natural flow of water. This article explores the methods used to restore the Kissimmee River to a functioning ecosystem.
The Environmental Damage Caused by Channelization
The original Kissimmee River meandered for approximately 103 miles through its broad, two-mile-wide floodplain in central Florida. This natural system featured slow, continuous flow and seasonal inundation of up to 40,000 acres of wetlands, supporting a diverse ecosystem. Between 1962 and 1971, the river was transformed into the C-38 canal, a straight, 56-mile-long drainage ditch built for flood control and navigation. The canal was dredged to a depth of about 30 feet, bypassing and isolating the original river’s bends, or oxbows.
This channelization had catastrophic environmental consequences. The rapid flow of the C-38 canal eliminated the seasonal flooding cycle, draining an estimated 12,000 to 21,000 hectares of floodplain wetlands. The loss of this habitat led to a decline in populations, including a decrease of over 90 percent of the waterfowl that once used the wetlands. Furthermore, the deep, stagnant pools created by water control structures became severely oxygen-depleted, decimating native fish communities that required flowing water.
The Core Strategy: Reestablishing the Historical Flow
The blueprint for restoration required a comprehensive strategy known as “dechannelization” to restore the river’s physical form and historical hydrological function. The goal was to reconnect the old, meandering river channels and reestablish seasonal sheet flow across 40 square miles of the historic floodplain. This plan mandated the physical restoration of 44 miles of the original river channel.
Achieving this required the acquisition of over 100,000 acres of land along the river and in the upper chain of lakes for public management. The strategy involved physically filling in the C-38 canal to divert water back into the remnant river channels. It also required removing several large water control structures, specifically the S-65 series spillways, which had compartmentalized the river into stagnant pools. Removing these structures was necessary to allow for the continuous flow of water once the canal was backfilled.
Engineering the River’s Return
The physical execution of the plan involved construction and deconstruction methods to undo the channelization. The most significant task was the backfilling of approximately 22 miles of the C-38 canal, accomplished in several phases. For example, the first construction phase involved moving 9.2 million cubic meters of earth to fill a 7.5-mile section.
The fill material was sourced primarily from the spoil mounds—piles of excavated earth originally dug up to create the C-38 canal—that lined the waterway. Engineers carefully graded this spoil material to mimic the elevations of the original floodplain. Using the existing spoil ensured the fill material was geologically similar to the surrounding landscape, promoting natural re-vegetation.
The process also involved removing major concrete structures that blocked the natural flow. The S-65B water control structure, for instance, was removed using explosive demolition to ensure a clean, rapid breach. Additionally, to link the backfilled canal sections to the preserved oxbows of the original river, engineers re-carved new sections of river channel. These new channels blended seamlessly with the historic meanders, ensuring water was properly routed and continuous flow was restored.
Immediate Ecological and Hydrological Response
Upon completion of the initial phases of backfilling and structure removal, the ecological and hydrological response was immediate. Removing flow barriers allowed water to spill out of the main channel, rapidly re-inundating the desiccated floodplain. This return of sheet flow triggered the recovery of the wetland ecosystem, reestablishing seasonal water levels.
The return to a meandering, flowing river system significantly improved water quality. Dissolved oxygen concentrations, which had been near zero in the stagnant pools, increased up to six-fold in restored sections, creating suitable aquatic habitat. The food web recovered swiftly, evidenced by an increase in native fish, such as largemouth bass and sunfishes, which comprised more than 63 percent of the fish community. Wading bird populations in the restored areas were observed to be over five times greater than pre-restoration levels.