NORTH PORT – In the days after Hurricane Ian struck, water flowing down the Myakkahatchee Creek as it entered the city approached a speed of 7,000 cubic feet per second.
That flow, recorded at a United States Geological Survey rain gauge at Tropicaire Boulevard, wasroughly seven times faster than the peak in July 2021, following Tropical Storm Elsa, and more than 13 times faster than peak flow afterHurricane Irma in September 2017.
The peakduring Elsa was 1,000 cubic feet per second, noted North Port Stormwater Manager Elizabeth Wong, and afterIrma it was 560 cubic feet per second.
Related: Sarasota, Manatee spared storm surge
And:As Myakka River basin drains, flood danger increases
Misinformation circulated about what exactly happenedat the Cocoplum Waterway adjacent to the Water Control Structure 106, a $2.47 million structure that plays an important role in North Port's interconnected stormwater drainage system, and whether that breach affected the severe flooding that occurred miles away at North Port Estates.
Water Control Structure 106 is one of 23 gated structures that help manage stormwater runoff in North Port. Public works employees open and close the gates to control the water flow. In addition to those the city has 41 weirs – where upstream water gathers until it spills over to continue flowing downstream – and drop structures, where collected water flows down into the drainage system.
The Snover and Cocoplum waterways are the two primary east-to-west waterways that carry runoff into the Myakkahatchee Creek.
Every north-south waterway flows into the Cocoplum Waterway.From there, water either flows into the city’s water treatment plant or into the Myakkahatchee Creek and then on to the lower Myakka River into Charlotte Harbor.
Sarasota County sent a3:15 a.m. alert Oct. 1 about a compromised levee near Hidden River – north of Myakka State Park – fuelingmore speculation inNorth Port-based social media groups about what happened at the Cocoplum structure, where erosion from the rapid water flow occurred.
In fact, the breach of the banks near the water control structure, at the far west side of the Cocoplum Waterway, did not impact North Port Estates, city officials said.
A combination of high water pressure on the Cocoplum Waterway – its flow gauge failed at about 4:15 p.m. on Sept. 28 – and persistent winds blowing from north to southcaused rapid erosion of the soilalong the Cocoplum.
“The water got so high that it went over and eroded the soft banks at the top,” Wong said. “You never expect the water to get so high.”
“The structure stood so nicely. It’s not tilted, no damage to the structure, it just eroded around the structure on the south side.”
The weir structure on either side of the gates – composed of sheet metal pilings with a concrete cap – held up fine, she added.
Zep Construction Inc. the original contractor on the water control structure, which was opened in late 2020,quickly stabilized the shoreline
“They were very, very good to work with, they came up very quickly and got that water main that was in the eroded area back into service” for the nearby Winn-Dixie shopping center along U.S. 41,Wong said.
Starting in the middle of last week, the city’s public works department beganlowering the water levelin the Cocoplum Waterway between Chamberlain and North Port boulevards to repair the canal.
Wong said water overflowed the south bank of the Cocoplum Waterway near Hillsborough Boulevard and the Charlotte County line, behind the Kia dealership.
Excess water flows on four Price Boulevard waterway crossings – at the McCaughey, Creighton, Lagoon and Blueridge waterways – impacted the road.
By Oct. 13 the McCaughey Waterway crossing had been restored and by Oct. 20 the Lagoon Waterway crossing had been restored. The others require utility repairs prior to restoring the roadway.
Failure of a structure on the Jupiter Waterway took out a portion of Chancellor Boulevard near Cornelius Boulevard and the southern border between the city and Charlotte County.
“That one took out the structure, completely clogged with all the debris, and the road started to wash out on the north side,” Wong said.
General Development Corp. built 81 miles of canals and waterways in the 1950s to transform wetlands into buildable lots for its North Port Charlotte development.
There are23 gated water control structures and 41 weirs that move water from property in the city to the Myakkahatchee Creek.
That system was designed to handle water flow in a 10-year storm event over a five day period.
Ian, which brought between 14 and 15 inches of rain within the city and 21.45 inches of rainfall northeast of the city, has been widely characterized as a 500-year storm event.
The Myakka River reached a new record flood level of 12.8 feet at Myakka River State Park – 5.8 feet above flood stage.
In 2009, the city started a program to finance replacement of the structures.The city hasa plan to finance replacement at a pace of about one a year using moneyfrom the road and drainage fees paid by city residents and the local one-cent sales tax.
At that rate, it would take roughly 50 years to complete the task.
City commissioners have talked about other options to fast-track that plan. It’s likely to be an issue as the city begins formulating its 2023-24 budget next spring and summer.
“We were improving them fast,” City Manager Jerome Fletcher told the Herald-Tribune on Oct. 15, when Federal Emergency Management Agency Administrator Deanne Criswell toured the Disaster Recovery Center at Shannon Staub Public Library. “But we need to be improving them even faster.”
Earlier:North Port faces financial dilemma with aging water control infrastructure
Related: City seeks to establish fund to replace water control infrastructure
Earle Kimel primarily covers south Sarasota County for the Herald-Tribune and can be reached at earle.kimel@heraldtribune.com. Support local journalism with a digital subscription to the Herald-Tribune.
