Says subsidence rate in Des Allemands levee is normal
St. Charles Parish President Larry Cochran refuted a recent report that stated the Sunset Drainage District levee has subsided at least half a foot from 2014 to 2018 and as much as 1.2 feet in one area, noting that while the levee indeed has subsided over that time, the publicized numbers were inaccurate.
A report by The Advocate published last month cited numbers collected by a team of scientists and engineers with the St. Charles Parish government that indicated the Sunset levee that protects 16.4 square miles — and the homes of more than 5,000 residents of Des Allemands, Paradis and Bayou Gauche — has subsided at least half a foot during that four year time span, with the most regression coming along Petit Lac Des Allemands, which reportedly dropped 1.2 feet, from 7.1 feet to 5.9, putting residents who live in those areas in increased danger of flooding.
Cochran and other parish representatives maintain those numbers were inaccurate and misrepresented the situation, saying discrepancies between the compared 2014 LiDAR survey and 2017 ground survey were a result of different elevation models used between the two data sets and not a result of subsidence. The parish asserted that during that span, 90 percent of the levee showed differences only between 0 and two inches and that 10 percent of the levee system experienced elevation changes between two and six inches. The parish adds the Petit Lac Des Allemands area showed a much smaller change than reported.
“For most of the levee, it was two inches, and where it was reported it subsided the most (Petit Lac Des Allemands), it was six inches,” Cochran said. “The information was reported prior to the data being processed and analyzed.”
Parish representatives said the rate of subsidence for the Sunset levee was typical and anticipated for a levee system.
The parish’s efforts to maintain the levee have drawn criticism from Councilman Paul Hogan, who says he believes the levees stopped being properly maintained when parish government took control of the Sunset Drainage District in 2013. Prior to that, levee maintenance fell under the jurisdiction of the Sunset Drainage District, an independent board consisting of local property owners.
“Sunset is a very integral part of the levee system,” Cochran said. “We were reminded by (Hogan) that we’ve done nothing with Sunset … we’ve spent in excess of $4.5 million and that’s a very conservative number.”
Specific upgrades included the reworking of the pump station with the addition of pumps, as well as addressing asbestos found at one of the buildings.
Cochran also said while further measures are planned, the parish cannot act alone, and is limited in what steps it can take to raise the levee.
“After Hurricane Katrina, things are done differently with levee maintenance … you can’t just dig and throw dirt on top of a levee (to raise it),” he said. “It’s important FEMA recognizes this levee. We can’t do anything to degrade it, and this degrades it, in their eyes.”
He added that the Lafourche Basin Levee District is in charge of the Sunset levee, and that the two are working together “to get the levee where it needs to be in the community’s eyes.”
Hogan acknowledged and applauded the parish for making the commitment and effort to fortify the pump station, but held firm in his stance that the levees themselves have not been adequately addressed, nor his requests to lay out a specific plan to raise the levee. He said an inquiry letter to Cochran was forwarded to the Lafourche Basin Levee District, which he said acknowledged the levee’s recession but did not answer his specific questions concerning the minimum amount of levee protection and what the plans to raise the levee will be in that case. He said multiple follow-up letters to Cochran have gone unanswered.
“Levees sink all the time. A plan has to be in place and there needs to be a minimum elevation,” Hogan said. “Where do we let it go down to? Elevation 3, before we say we’ve got to raise that spot? I’m not concerned with the Lafourche Basin Levee District or that you entered into an agreement with them. You have an agreement with us. My issue is with the parish and they have to answer.”
Long term, the ultimate hope lays with the $940 million federal Upper Barataria Risk Reduction project, under which the Sunset Drainage levee falls. That projects to raise the Sunset levee to 12.5 feet.
“That will be our savior one day,” Hogan said. “But that’s years down the road. We can’t wait for a levee that for all we know may never be built.”
Sunset Drainage District Levee
- Sunset Drainage District Levee protects the homes of more than 5,000 residents of Des Allemands, Paradis and Bayou Gauche.
- Parish maintains 90 percent of levee has shown elevation loss of between 0 and two inches, with the Petit Lac Des Allemands area showing the most change at a loss of six inches.