Only minor levee deficiencies in updated elevation reports -- Wax Lake East levees were surveyed
MORGAN CITY, La. — After meeting with the U.S. Army Corps of Engineers on May 20, it now appears as though the St. Mary Parish Levee District will be able to keep the base flood elevations for communities in the eastern part of St. Mary Parish at near the same level, which is a determining factor for flood insurance rates.
Updated Levee System Evaluation Reports on the Wax Lake East levees, which protect Patterson, Bayou Vista and Berwick, show only minor deficiencies in the levees instead of the seven to eight feet deficiencies the original reports showed, St. Mary Parish Levee District Executive Director Tim Matte said.
While the updated Levee System Evaluation Report still says the Wax Lake East levees are deficient, the levee district now just has to deal with several one- or two-foot dips in the levees.
The U.S. Army Corps of Engineers produces maps and is a contractor to FEMA to prepare some of the data for the FEMA Digital Flood Insurance Rate maps, Matte said.
The levee district turns to the corps to certify the levees because the corps built most of the levees in the parish.
The corps produced the original report presenting it to the levee district in February to the “shock” of those involved with the St. Mary Parish levee district, Matte said.
“It affects not just the flood insurance rates for the residents that live there but also the businesses that are located within those particular areas,” Matte said.
FEMA released the current Digital Flood Insurance Rate maps in 2008, but presumed all of the levees were certified, Matte said. It was up to the communities to then make sure the levees were certified, he said.
The corps is also working on a report on the Wax Lake West levees, which the original report showed to have deficiencies similar to the Wax Lake East levees, Matte said. Matte expects the new Wax Lake West levees report will have similar results to the Wax Lake East levees showing only minor deficiencies this time around.
The corps evaluated several other levee systems in its original Levee System Evaluation Reports released in February, but the Wax Lake East and West levees showed the greatest deficiencies at the time according to the reports, Matte said.
In the Wax Lake East area, the levee district will probably be able to keep residents’ base flood elevations at the same level, which is a factor in determining flood insurance rates.
There are still a few spots on the Wax Lake East and West levees the levee district will have to address, but will be able to do so without much cost.
The levee district hired T. Baker Smith to do the re-analysis of the levees to see whether the corps’ original reports were accurate. The engineers picked two locations along the Wax Lake East and West levees and took elevations of the ground on the toe of the levee so they knew what the elevation of the levee on the flood side was.
The corps assumed that there was nothing impeding the wave when it did its original analysis, not taking into account any vegetation that would slow down waves coming in.
T. Baker Smith engineers went into the field and actually measured trees taking a representative sample and included that information in the calculation of what the wave run-up should be, Matte said.
“Instead of calculating a wave run-up that would go across this whole area, they, in effect, are calculating a wave run-up across the Intracoastal Waterway,” Matte said. The levee district presented the information to the corps and the corps met with the levee district on May 20 and presented the levee district with an updated
In light of the elevation requirement changes in the corps’ report, the corps must now go back and do all the geotechnical work to make sure the levees are stable. Matte said he was told the corps expects to finish the final reports by the end of July.
The next step for the levee district is to specifically identify any spots on the levees that need to be raised or repaired and determine what materials would be needed and how much the work would cost, so that either the levee district, the state, federal government or a combination thereof could do that work, Matte said.
The goal is to get the levees to the point where the corps can come in and certify the levees.
The engineering re-analysis from T. Baker Smith cost about $15,000, but said it paid off, Matte said. “Otherwise, I don’t know that we would have gotten the right response out of the corps,” Matte said.