St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District
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Water bodies, watersheds and storm water

Understanding flooding and water flow

The St. Johns River’s Upper Basin Project and Canal 54
The Upper St. Johns River Basin Project is semi-structural. Water control structures at Canal 54 channel water near the Stick Marsh.

The Upper St. Johns River Basin Project is semi-structural. Water control structures at Canal 54 channel water near the Stick Marsh.

Extreme rainfall can cause the St. Johns River to surge beyond its banks, damaging homes and businesses along the river and its lakes.

After a devastating flood in the 1940s, the Upper St. Johns River Basin Project was planned to control flooding on the St. Johns River in Osceola, Brevard and Indian River counties. One component of this project is Canal 54 (C-54). Located along the county line of Brevard and Indian River counties, C-54 was originally designed to divert water from the upper St. Johns River into the Indian River Lagoon. The upper basin project was redesigned in the 1980s to address environmental concerns with the original design and the role of C-54 changed.

As part of the original upper basin project, C-54 discharged directly from the St. Johns River to the lagoon. However, C-54 is no longer directly connected to the St. Johns River, but instead serves only as an emergency overflow for the St. Johns Water Management Area to ensure that extreme flood events do not overtop the flood protection levees.

Flooding occurred in the middle St. Johns River Basin in 2004; this scene at the State Road 46 bridge near Lake Jesup on Sept. 30, 2004.

Flooding occurred in the middle St. Johns River Basin in 2004; this scene at the State Road 46 bridge near Lake Jesup on Sept. 30, 2004.

In the historic and unprecedented 2004 hurricane season, nearly 4 feet of rain fell on east-central Florida during a 60-day period. The rainfall statistics were phenomenal — a series of storms that would only be expected once every 200 years. Both water levels and frustration levels were especially high in the Middle St. Johns River Basin (Lake Harney north to Lake George, including lakes Jesup and Monroe), and as the river overran its banks, some called for the St. Johns River Water Management District to provide flood relief by releasing water from the St. Johns River to the Indian River through C-54, located about 120 miles to the south.

Contrary to popular belief, the use of C-54 to release water from the headwaters of the St. Johns River would have provided no flood relief to the middle basin (east-central Florida). During the 2004 floods, the upper basin project operated as designed to provide flood relief within the project area. However, the project does not provide flood protection in the middle St. Johns River and there are no similar flood protection facilities in the middle St. Johns River area.

Canal 54 stretches from the St. Johns River to the Indian River Lagoon.

Canal 54 stretches from the St. Johns River to the Indian River Lagoon.

When the St. Johns Water Management Area is full, discharges to the St. Johns River are halted and discharges are made through C-54. Following Hurricane Frances (September 2004) when discharges were made through C-54, the result was a reduction in flow to the St. Johns River of only 600 cubic feet per second (cfs). Water management district engineers estimate that a 600-cfs reduction in flow from the upper basin project would have resulted in less than a half-inch reduction in the water level on Lake Monroe. Why such a small impact? Because flows out of the uncontrolled tributaries of the middle St. Johns River are much larger than this. For example, flow out of the Econlockhatchee River has been measured at more than 10,000 cfs, and this is only one of several tributaries of the middle St. Johns River.

Downstream of the upper basin project area, flood levels are reduced as far north as Lake Poinsett. For example, flood elevations on Lake Washington can be reduced by about half a foot for the 100-year flood event. However, as with any flood protection project, there are limits to the level of flood protection benefits and the areas benefited by the project. While the project reduces flooding in much of the upper St. Johns, it does not eliminate flooding in many areas. The project does not reduce flooding in the river’s middle basin in east-central Florida, including Lake Monroe. This is due to the fact that additional areas drain to the middle basin, such as the Econlockhatchee River and other tributaries that do not have comparable flood control facilities.

Water management district engineers have concluded that the flooding that occurred on lakes Monroe and Harney in 2004 was due primarily to local rainfall conditions and that greater use of C-54 would not have reduced the damage caused by these floods.

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St. Johns River Water Management District
4049 Reid Street, Palatka, FL 32177
(800) 725-5922