Withlacoochee Update (Post-Milton) - 10/16/2024

Withlacoochee River Still Rising

 

River levels have peaked in the Green Swamp but are still rising along the remainder of the river.

 

Note: In the update below, I’ve included links to the USGS gauge conditions so you can keep an eye on what the river is doing in different areas.

 

Historic Flooding:

• Hurricane Milton brought double-digit rainfall to our region at the end of our wet season; a time when our lakes, streams, wetlands, ponds and aquifer levels were already full.
• The Withlacoochee River is experiencing major flooding and most areas are still rising.  
• Places that haven't flooded in decades are now inundated with water.
• Some areas that didn't receive as much rainfall are still filling up as water continues to move from higher elevation to lower elevation land.  
• It'll take time for the floodwaters in many of these areas to recede from the historic flooding our region is experiencing.

 

Floodwaters Are Still Rising in the Lacoochee Area Near Trilby (October 14, 2024)

 

Little Withlacoochee River (Sumter/Hernando Counties):

• The Little Withlacoochee River at US 301 crested on Saturday afternoon at a level that was 1.5 feet higher than the peak of Hurricane Irma in 2017.
• Water levels haven’t really dropped yet and are holding within an inch or so of that peak level.
• Over the next several days, the Little Withlacoochee should start dropping but it may not fall below flood stage for another couple weeks.

 

 

 

Withlacoochee River (Green Swamp to the Gulf of Mexico):

 

Green Swamp

• Current flooding in the Green Swamp is the highest it’s been since 1960, surpassing both the peaks from Hurricane Irma (2017) and the 2004 hurricanes.
• The Withlacoochee River at SR471, in the middle of Green Swamp, crested on Saturday and has fallen about 10 inches since then.
• At the Dade City gauge on the west side of the Green Swamp, river levels crested Sunday morning and are slowly receding.
• Many homes in Dade City near the Withlacoochee (River Rd) may continue to see rising water as the floodwaters attempt to level out nearly a mile from the rivers center.
• There are no water control structures in the Green Swamp that could hold back or divert any floodwaters.

 

Trilby and Ridge Manor

• The Withlacoochee River at Trilby (US301) is now 1.6 feet higher than the Hurricane Irma peak and it continues to rise.
• The National Weather Service is currently predicting Trilby to rise a few more inches and should peak by this weekend.
• The river at Trilby has already risen 10 feet since Hurricane Milton.
• Near Ridge Manor (SR50) the river is now 0.7 feet higher than the Hurricane Irma peak and continues to rise.
• The river near SR 50 could still rise more than 6 inches, possibly peaking by the end of this weekend.
• Flooding at Trilby and Ridge Manor are now the highest they’ve been since 1960.
• River flows at Trilby are now 50% higher than were at the peak of Hurricane Irma!

 

Nobleton and Hwy 48

• Downstream at Nobleton (CR476), the Withlacoochee River is still rising sharply.
• River levels there have already surpassed the peaks from both Hurricane Irma (2017) and the 2004 hurricanes.
• The river at Nobleton may continue to rise for another week, possibly rising another 2 feet.
• At Hwy 48 (between Floral City and Bushnell), river levels also continue to rise but not as fast as Nobleton since the river spreads out there.
• River levels are expected to continue rising at Hwy 48 for at least another week and may still rise 1-2 more feet before they peak.
• The Leslie Heifner structure was opened today to move some water into the Tsala Apopka Chain of Lakes, but there is no way to significantly lower water levels on the Withlacoochee River.

 

Hwy 44 and Hwy 200

• River levels at Hwy 44 continue to slowly rise, and are now a few inches below peak levels from Hurricane Irma.
• The river will continue rising at Hwy 44 for at least 2 more weeks and water levels could end up 1-2 feet higher than they are today.
• At Hwy 200 (Holder), the Withlacoochee River is currently within a couple inches of the peak from Hurricane Irma.
• The National Weather Service is predicting Hwy 200 will rise a few more inches this week, but that won’t be the end of it.
• River levels still haven’t peaked 60 miles upstream and all that water still must make its way down to Hwy 200.
• The river at Hwy 200 will continue rising for at least another 2-3 weeks and may rise 2 to 3 feet higher than it is today.

 

Dunnellon and Lake Rousseau

• At Dunnellon (Hwy 41), the Withlacoochee River is still slowly rising as it reaches minor flood stage. River levels will keep rising there for another few weeks.
• On Lake Rousseau, the Inglis Dam, which was opened on August 3^rd, remains open discharging high flow to the Barge Canal.
• The lake remains lowered as river levels upstream near Dunnellon continue to rise.
• The Inglis Dam has no effect on river levels upstream near Hwy 200. Flooding from the Green Swamp downstream past Hwy 200 is the result of natural river flows and channel bottom elevations (topography).

 

Lower Withlacoochee River

• The Inglis Bypass Spillway is fully open, discharging high flows to the Lower Withlacoochee River.
• The Inglis Dam is also open discharging rising river flows into the Barge Canal.

 

 

 

Tsala Apopka Chain of Lakes (Citrus County):

• Prior to Hurricane Milton, structures were open releasing water from the Tsala Apopka Chain of Lakes.
• The Leslie Heifner structure on Trails End Rd is now open, moving water into the lakes from the flooded river.
• All structures that release water from the lakes remain open discharging water to help make room for incoming river flows.
• As river levels at Hwy 200 continue to rise from floodwaters upstream in the Green Swamp, we are monitoring our discharges from Tsala Apopka.
• We plan to close the S-353 structure in the coming days so that excess lake water is not flowing into Hwy 200 when the river reaches major flood stage.
• A common misconception is that we can prevent flooding along the river by keeping lake levels down or moving water into or out of the lakes, but that is simply not the case.
• Flooding along the Withlacoochee River occurs naturally when we receive widespread heavy rainfall on an already saturated landscape at the end of the wet season.

 

 

Lake Panasoffkee and Wysong Structure (Sumter County):

• Lake Panasoffkee also continues to rise.
• Flows entering the lake from Little Jones Creek and Shady Brook remain extremely high.
• Rising river levels will also slow down how fast the lake can drain to the Withlacoochee.
• The Wysong Structure on the Withlacoochee River, which was fully lowered in early August, remains fully lowered.
• Lake Panasoffkee is expected to rise for another couple weeks (maybe another 1 to 1.5 feet), as upstream floodwaters drain into the lake and the Withlacoochee River downstream continues to rise.

 

-Mark

 

 

 

 

Mark Fulkerson, Ph.D., P.E.

Chief Professional Engineer

Southwest Florida Water Management District

 (352) 269-6073 (office)

(352) 279-4493 (cell)

Mark.Fulkerson@WaterMatters.org

 Withlacoochee River Watershed Initiative