Letter to the Editor: Sunset levee subsidence exaggerated

To the Residents of St. Charles Parish,

The purpose of this letter is to clarify some misconceptions contained in an article published in The Advocate on Dec. 12, 2018. The article stated that almost the entire Sunset Drainage District Levee (SDDL) has subsided at least half a foot from 2014 to 2018, with one area along Petit Lac Des Allemands dropping to 5.9 feet this year, down from 7.1 feet in 2014. That information however, is not just exaggerated, but also misrepresents the existing conditions along the SDDL. Recent analyses show that during that time period, the levee subsided at a rate of approximately half an inch per year, which according to scientists and engineers, subsidence is not only typical for a levee system it is also anticipated. During that span, roughly 10 percent of the levee system experienced elevation changes between 2 to 5 inches with about 90 percent only showing differences between 0 to 2 inches (See Figure 1 below). The results show that the majority of the elevation differences were located along the southern stretch of the levee near the Bayou Gauche Pump Station. Areas along Petit Lac Des Allemands and along the Paradis Canal showed very little change, which is contrary to the article published in The Advocate.

Unfortunately, the information reported by The Advocate suggests otherwise because not only was the article published before analysis of the 2017 survey data was completed, parish officials were not contacted for comments to verify the information that was provided to them. Although initial comparison of the data showed differences between the 2014 LiDAR survey and the 2018 ground survey, it wasn’t until subsequent analysis of the 2017 survey data that those discrepancies were found to be just a result of different elevation models used between the two data sets and not a result of subsidence. Nevertheless, the article created the impression that the amount of subsidence was greater than it actually was. In addition to this, the article also claims that the subsidence was due to lack of maintenance. Since 2014, when the parish took over control of the Sunset Levee, more than 4.5 million dollars has been invested into the levee to ensure it is not only maintained, but that it also meets the engineering standard of care.

Our main goal for the Sunset Levee has been a holistic one with the intention to provide complete protection to all of the residents on the Westbank of St. Charles Parish. Currently, we are working with engineers and FEMA to ensure the levee stays within the engineering standard of care so we can continue to flood fight while seeking additional federal funding. The mission of St. Charles Parish government is to always work towards improving the quality of life for our residents and at the forefront of that mission is levee protection for every single resident. We will continue to stay dedicated to maintaining the SDDL just as we are with the entire levee system.

Sincerely,
Larry Cochran
St. Charles Parish President

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