Tampa Bypass Canal

The Tampa Bypass Canal is a Southwest Florida Water Management District (SWFWMD) flood channel that carries Hillsborough River floodwater around Temple Terrace and Tampa to McKay Bay.

According to the SWFWMD project page, the canal runs parallel to the Hillsborough River and empties into McKay Bay on the east side of Tampa, and several water control structures along it let the District manage the flow of water into and through the channel. It diverts the flood water captured in the upstream reservoir around the two cities instead of letting it pass down the lower Hillsborough.

The canal is one piece of what SWFWMD calls the Tampa Bypass Canal System, together with the Hillsborough Flood Detention Reservoir and the Harney Canal. District sources give different lengths, and the page reports all three rather than choosing one: the project page says approximately 15.7 miles, the SWFWMD recreation page calls it a 14-mile waterway connecting the Lower Hillsborough Wilderness Preserve with McKay Bay, and a 2004 District article describes a canal more than 12 miles long built along with six dams, or flood-control structures.

The canal was built because Hurricane Donna flooded Tampa in 1960 and Florida answered by creating SWFWMD in 1961 to sponsor a federal flood control project.

SWFWMD's history of its first decade records that during the 1960 hurricane season Donna hammered Florida with 128-mph sustained winds and massive flooding, and the District's project page states that Tampa experienced significant river flooding caused by rainfall, runoff and storm surge. The Florida Legislature created the District in 1961 by special act to be the local sponsor of the Four River Basins, Florida Project, and its Board of Governors held its first meeting on August 28, 1961, in Tallahassee.

The Four River Basins project was a $57 million flood control plan designed by the U.S. Army Corps of Engineers for a 6,000-square-mile area including the Hillsborough, Ocklawaha, Peace and Withlacoochee river basins. The Corps designed and constructed the canals, bridges and flood control structures, while the District's job was to acquire the land and agree to operate and maintain the project.

The new District organized around local watersheds. By March 1962, SWFWMD reports, its 11 watershed Basin Boards were organized, including boards for the Hillsborough River and Northwest Hillsborough, and the Governing Board and a staff of three held monthly meetings in a rented Brooksville office. Dale Twachtmann, executive director from 1962 to 1972, recalled that the District immediately began buying land for flood control, including land for the Tampa Bypass Canal and large amounts of acreage for the Lower Hillsborough River Flood Detention Area.

SWFWMD dates engineering and recreation planning for the Tampa Bypass Canal to 1963 and the groundbreaking on its first section to 1966.

A District photograph in the same history shows the S-160 Flood Control Structure under construction in 1968, and SWFWMD says the bulk of the canal system was built in the District's first decade. The lower end of the channel follows the Palm River; a SWFWMD release of October 27, 2011 notes that the Palm River is part of the canal, flows from S-160 just north of the Selmon Expressway to the mouth of McKay Bay, and required significant dredging during canal construction in the 1960s. Erosion from that work was identified in the 1970s, and in 1976 Hillsborough County and the District installed rock riprap and vegetation to control it.

Weather turned the other way while the work went on. Memories of Donna faded as the region slipped into drought from late 1962 into 1963, and the District's first executive director recalled residents asking why money was going to flood control when their problem was a lack of rain. The project page adds that residents raised concerns about dry wells, sinkholes and ecological impacts. In 1969 SWFWMD asked Congress to expand the Four River Basins project to add a multipurpose aspect; the District changed the design of the system to help the City of Tampa with its public water supply, and the former director said the change let Tampa use some canal water for drinking water.

One planned feature was dropped. SWFWMD's Lower Hillsborough Wilderness Preserve page explains that the preserve was designed for temporary impoundment of floodwaters, with a levee on its western boundary, a dam on the Hillsborough River and the Tampa Bypass Canal to reroute the water, and that a structural reservoir in the original plan was later abandoned as the value of natural wetlands for flood storage came to be understood.

The canal protects Tampa by letting SWFWMD close Structure S-155, hold the Hillsborough River in a 16,000-acre detention reservoir and divert the water around Temple Terrace and Tampa.

The project page explains that a 6.5-mile-long earthen dam is associated with the Hillsborough Flood Detention Reservoir, which remains empty until it is needed in times of high water. The river flows through the dam by passing through S-155; closing S-155 stops that flow, the reservoir begins to fill, and water can then be released to the river or diverted to the canal around the two cities.

The District's WaterMatters magazine for November to December 2004 adds the river's scale: nearly 700 square miles drain into the 55-mile-long Hillsborough River, which runs from the Green Swamp north of Lakeland to Hillsborough Bay. It places S-155, the northernmost structure, near where the river intersects Interstate 75 just north of Fletcher Avenue, where two 24-ton gates can redirect all or part of the river flow, accounting for drainage from approximately 452 square miles. Farther downstream, the Harney Canal connects the river to the bypass canal a few miles north of the City of Tampa's dam, and SWFWMD opens it when inflows downstream of the earthen dam cause river flooding, especially when storm surge impedes discharges from the city dam. When not needed for flood control, more than 7,000 acres of the detention area are used by Hillsborough County as a regional park.

The 2004 hurricane season tested the system. After Charley, Frances and Jeanne, the Alafia, Peace and Withlacoochee rivers flooded, but SWFWMD reported that homes and businesses on the lower Hillsborough were spared because of the canal and the flood detention area. That year the canal diverted more than 200 billion gallons from the river, an average of 3.5 billion gallons per day, and ran three times for a total of 58 days, while the District normally operates it once a year in coordination with the City of Tampa.

The canal doubles as a freshwater supply for the Tampa Bay region and as public land for boating, fishing, hiking and bicycling.

SWFWMD describes the canals as large linear pools of fresh water used by local utilities to supply the region. Tampa Bay Water states that surface water has been treated at its plant since late 2002, and that when available, water is skimmed from the Alafia River, Hillsborough River and the Tampa Bypass Canal; some is treated for immediate use at the Tampa Bay Regional Surface Water Treatment Plant and surplus water is stored in the 15.5-billion gallon Bill Young Regional Reservoir for dry times.

SWFWMD's recreation page divides the canal at SR 60. North of SR 60 the water is fresh, motors up to 10 HP are allowed and the reach is a no-wake zone, with boating access from Harney Canal Park off US 301; south of SR 60 the water is salt and powerboating is allowed with no restrictions, with access from McKay Bay or private ramps. Bank fishing is allowed from public access points and parks along the canal, hiking follows the grassy canal bank from designated access points, and the site is open daily from sunrise to sunset.

Last verified: October 18, 2026, by re-reading the SWFWMD canal system, Tampa Bypass Canal recreation and Lower Hillsborough Wilderness Preserve pages, the District's 1960s history, its 2004 WaterMatters account and 2011 Palm River release, and Tampa Bay Water's surface water page.