Mandeville weighs options to improve flood protection


Cyclists ride down Mandeville’s lakefront on a sunny day. The seawall pictured is regularly overtopped during tropical systems, leading to inland flooding. Photo credit: Barbara Brown

Barbara Brown

As Mandeville continues to see routine flooding from tropical systems, residents near the city’s lakefront are considering options to improve drainage and protection systems.

Flooding from nearby tropical systems has long just been a part of life on the lakefront, where most homes are raised to offer protection from surge that comes with major storms.

The most recent flood didn’t come from a major storm, though.

It came from Tropical Storm Cindy in June, which made landfall hundreds of miles to the west with 40 mph winds, yet still managed to flood the city for several blocks inland in some places.

This inundation from such an insignificant system, and one that made landfall so far away, has brought calls for the city to do something to address the problem.

Lakefront resident and business owner Gerard Braud said there are three weather events that can cause lakefront flooding. One is from strong winds pushing the water from Lake Pontchartrain over the seawall, another is from excessive amounts of rain from localized storms and the third, and most significant, cause is from major hurricanes.

While there are no current plans for flood protection, City Council chairwoman Lauré Sica said there was a study conducted this year on modeling for what the city could do, which then led to another study.

When reviewing flood protection options, there should be a three-prong approach, Braud said. The first should be to raise the lakefront’s seawall by two feet. The seawall sits 5 feet 2 inches above sea level. Strong winds can cause waters to lap by one or two inches, which has the ability to flood several blocks.

Sica said the seawall was last replaced in 1995 and has a 30-year shelf life. The seawall isn’t there yet, so small repairs will be made when needed until the decision comes to replace it. She said when the city does replace the seawall, it will depend on how high the lake is and drainage issues.

“Is the answer a higher seawall? I don’t know, but it’s not going to happen right now,” Sica said.

Flood insurance rates could go down if they do raise the seawall, Braud said, who added it would bring an economic benefit to everyone — not just the wealthy.

“If we do raise the seawall, it would change the flood maps for everyone on the east side of Mandeville,” Braud said.

The second approach sould be to build a gate that would come down across Bayous Coquille and Lavigne to prevent lake water from flooding these bayous. The third, Braud said, sould be a small affordable pumping station to remove incoming water more quickly.

“Some storms you simply can’t do anything about. Even Harvey caused water to come over the seawall with 10 foot waves,” Braud said. “A small pumping system could take the water out at the same pace that it comes in.”

The net issue is whether or not the city can afford to modify the existing seawall or whether it has to be replaced and torn down, Braud said.

Some may disagree with a change to the seawall, Braud said. The wall currently comes up to the mid-calf of most people. Raising that height to mid-thigh could cause an obstruction of view for some.

“The main thing I want to know is: What is the plan? How soon can a plan be drafted and how soon can work get started on a plan?” Braud said. “Too many people just look at one small piece. There is water drainage, flood insurance, having a pump and major storms all to consider.”