SWFWMD engineer: Withlacoochee gauges dropping upstream, but rainfall deciding factor on flood levels

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SWFWMD engineer: Withlacoochee gauges dropping upstream, but rainfall deciding factor on flood levels

Fri, 08/31/2018 - 19:31
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SWFWMD (Southwest Florida Water Management District) Senior Professional Engineer Mark Fulkerson, Ph.D., P.E presented to the Board of County Commissioners at the regular meeting on August 28, 2018 the current condition of the Withlacoochee River, and gave some insight on its history, impacts of seasonal rainfall, and flooding considerations for the future.

The third-largest river in the state, behind the St. John’s and Suwanee rivers, the Withlacoochee is 160 miles long, with associated streams, lakes and wetlands.    Its watershed, the land that the river interacts with, consists of over 2000 square miles and covers all or part of eight counties. Fulkerson describes it as a “large ... complicated river.  There’s a lot of dynamics that drive how it flows, but rainfall’s really the key.” Summarizing studies, he added, “We don’t have as much control as we think we do.”

According to Fulkerson, awareness of the river began in the 1830s-40s,  when steamboats were transporting soldiers and supplies during the Seminole Wars.  In the late 1800s, burgeoning industries of citrus, timber and phosphate relied on the river as well.   Today, the river’s purpose is recreation.

The first recorded flooding of the Withlacoochee was recorded in Trilby in 1833.  Fulkerson reported that the Trilby flooding was the highest ever recorded, seconded by the flooding on US Hwy 50 during hurricane Irma.   Using photos for contrast, Fulkerson also showed photos of extreme drought conditions, where the Withlacoochee was reduced to little or no flow in 2000 in Nobleton, and in 2007 in the Croom area.  He reports that more recently in 2012 and early 2017, there were areas of “little to no flow.”

Fulkerson explained that fluctuations in the Withlacoochee are primarily due to rainfall, however, rises in water level are not immediately apparent after a heavy rain.  He gave the example of how different areas of the river peaked at different times, up to ten days following Irma.  Calling it a “living, breathing system,” he further explained why the river doesn’t rise or flood uniformly,  “if (the entire river) was the same geometry, and level all the way down, and uniform,” water levels would be the same for all points of the river.  Since the landscape varies along the river, water will be forced to flood stage at different times in different places.

Rainfall so far in 2018 has not only surpassed 2017, but also the average rainfall in a given month. As a result, the Withlacoochee level began the year at a higher level, and continues to rise in accordance with rainfall.  As of this writing the level at US Hwy 50 in Ridge Manor is roughly 3 feet higher than 2017.

BOCC Chairman Steve Champion asked Fulkerson about potential flooding mentioned in recent local news reports.  Fulkerson advised that “gauges upstream are going down.” He believes that the Withlacoochee will peak over the next day or so, but the amount of rainfall will be the deciding factor.

Fulkerson concluded his presentation with mentioning that he and his team are in communication with Hernando County Emergency Management and Public Works. He added, “I’m committed to keep learning.  I don’t know it all,” and encouraged continuing cooperation between relevant agencies and departments.

Chester Bradshaw, an environmental conservationist from Sumter County addressed the board to refute Fulkerson’s findings.  Bradshaw stated that in 1996 he submitted documents to the Withlacoochee Regional Planning Council and to the Tampa Bay Regional Planning Council, regarding the same topics presented by Fulkerson.

Bradshaw’s experience and credentials are unknown, but he has recently given presentations as a “Grassroots Conservationist” and sat on an advisory board for the Southwest Florida Water Management District in 1994.

Bradshaw said that his documentation was based on “antique” US Geological Survey documents from 75 years ago, which “tell a very different story from what you’ve just heard.”  According to Bradshaw, facts given by Fulkerson are “inaccurate and misleading.” Presenting the board with a “Request for Action,” Bradshaw invited Fulkerson to explain differences in his findings, and how “the bridges seem to be plugged.”  Fulkerson did not return to the podium.

 

More information:

USGS Water Data for the Nation: waterdata.usgs.gov/nwis

Southeast River Forecast Center:  weather.gov/serfc

Withlacoochee River Watershed Initiative: watermatters.org/withlacoochee

 

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