Dredging the Vermilion comes full circle — as a navigation project

Flood events in Lafayette, especially the devastating floods of 2016, have LCG moving quickly to address residents' concerns ahead of the next big storm. But questions remain about how much benefit the tens of millions it is spending will have. Photo by Travis Gauthier

In the 1940s, the U.S. Army Corps of Engineers was authorized to dredge the Vermilion River to make it navigable for watercraft. Eighty-one years later, the funding has come through — in the middle of a heightening panic about flooding in the Acadiana region.

Just before the pandemic, the idea of dredging the river’s path in Lafayette Parish to abate floodwaters was shelved for lack of demonstrated benefit. Now, $50 million has been set aside to restore the river’s navigability, not stop flooding. Dredging the river has come full circle.

The massive federal investment announced last month by U.S. Rep. Clay Higgins took pretty much everyone by surprise — even the Corps, it would seem. The federal money train trailed a new $5 million commitment from Lafayette’s City Council, this time by an emergency ordinance passed unanimously just days after May’s flash flooding event. The federal windfall injects both inevitability into the project and kicks up new uncertainties about when it will happen and how it will work.

While dredging was locally heralded as a flood mitigation strategy, the Corps is moving forward with a different justification. It’s not a flood risk strategy, a Corps spokesman tells Straight News Online; it’s a navigation project. Where we go from here will depend on federal guidance not yet received. It’s unknown where the Corps will dredge, for how long or even where it will put the spoils.

That brings the effort into a strange limbo. Lafayette could move forward with $5 million worth of “spot” dredging, pending a permit. But it may duplicate the Corps’ own efforts, even if the big dredge isn’t coming quickly.

LCG is still preparing to spot dredge, according to City Councilwoman Nanette Cook, who lives on the river and has championed the project. City-parish engineers believe clearing “hotspots” in the river could increase the river’s capacity, Cook says, relaying the sentiments from a meeting this week.

“We just feel like there’s a little more urgency,” Cook says of moving ahead of what could be a longer federal timeline. “If needed and allowed, let’s see what the money we have can do.”

There’s no modeling yet to support whether removing hotspots — mounds of sediment accumulating where coulees meet the river — would have an appreciable impact on the river during a storm. Other projects proposed and budgeted by LCG, like knocking down the river’s banks to flush water into Cypress Island swamp behind Lafayette Regional Airport, could have greater benefit at the same or lower cost. LCG met with airport officials this week to discuss the project, according to Cook.

Science so far has not found dredging the Vermilion to be a cost-effective flood management strategy. Internationally, researchers have begun to view it as an outdated practice, and the project does threaten downstream impacts whether it’s done for navigation or some other purpose, according to modeling contracted by the Corps. While the Corps is moving it along on a separate track, following new financial channels dug by the White House in its proposed budget, it will nonetheless need to check the right boxes.

“We have to understand what we’re doing and the impact of what we’re going to do,” Corps spokesman Ricky Boyett says. In the coming weeks, the Corps will convene the parishes along the river to get everyone on the same page.

Lafayette’s rush to budget for dredging in May, just days after flash flooding stalled scores of cars in drive-home traffic, was predicated on a no-harm basis. Mayor-President Josh Guillory, who coordinated with City Councilwoman Liz Hebert to convene the emergency meeting, made incorrect assurances that Corps modeling showed downstream harm to be “pretty much nonexistent.” The Corps' report, based on prior modeling performed by the Louisiana Watershed Flood Center at UL, found dredging just part of the river could raise water levels in Vermilion Parish.

The administration did not respond to emails and phone calls requesting clarification or comment. Hebert could not be reached for clarification.

Two years ago, the Watershed Flood Center was contracted by the Corps to test the feasibility of dredging the river as a flood intervention. The results came back wanting in early 2020, drawing criticism from a movement rallied by grassroots water management advocates Dredge the Vermilion. Just months before the release of that feasibility study, Lafayette Consolidated Government put $5 million on the books to fund the project in response to swelling demands from flood-anxious residents.

Soberly, Rep. Higgins broke the bad news of the report’s findings. Dredging was no “silver bullet,” he said at a press conference in February 2020, weeks before the pandemic drowned out flooding as the preeminent crisis. The issue went publicly dormant from there.

The dynamics are different this time around. Instead of breaking the bad news, Higgins brought tidings of big funding last month when he announced the $50 million plugged into the Corps’ budget days after LCG’s emergency appropriation. Should it make it into the Corps’ work plan, highly likely at this stage, the Corps will dredge.

“That’s like making it to the one-yard line, but you haven’t scored yet,” Higgins says. The last yard is congressional authorization of President Joe Biden’s budget for 2022, according to the Corps’ Boyett, and whatever environmental permitting and planning is required.

Between the council’s commitment and Higgins’ appropriation, the flurry of funding surprised officials in Vermilion Parish. Representatives there have been wary of what digging out the river would do downstream and have consistently leveled those concerns when agitation to dredge spun up in Lafayette in recent years.

UL’s modeling for the Corps showed that dredging just part of the river within Lafayette’s city limits could back up the river downstream and raise water levels by 2-3 inches in Vermilion Parish. The benefit upstream is likely minor, too. Spot dredging, in all likelihood, would mean even less dirt removed. A peer-reviewed paper released by Flood Center Director Emad Habib in March of this year raises not just doubts about how effective dredging would be but potentially problematic ecological impacts: Dredging at a large scale could allow salt water from the Gulf to flow far upstream.

Whether spot dredging would substantially reduce flood risk is untested. Three months ago, LCG contracted Pam Granger, Youngsville’s city engineer and Dredge the Vermilion board member, to do more modeling as an extension of the ongoing review of the Homewood detention project, a large-scale effort that’s drawn some neighborhood opposition. Granger’s report is due June 14, and she tells Straight News Online the model will show benefit, while declining to offer specifics until the report is completed and delivered to LCG.

Whatever impact dredging may have, there is growing consensus the project alone, regardless of scale, is insufficient to deal with recent flooding. UL’s research suggests the river has little to do with flooding Lafayette Parish, beyond the homes on the river’s banks. Habib’s paper showed that partial dredging, 17 miles within city limits with deep excavation, would reduce the flooded area by 289 acres in the conditions of a historical storm like the 2- to 10-year rain event that inundated Carencro in 2014. That event flooded 44,790 acres and was a storm of similar intensity to the rains we saw in May.

“Our paper showed there are benefits,” to dredging, Habib says. “It begs the question: Are there other more effective solutions? Your objective is not dredging. The objective is to reduce flood risk.”

What Lafayette faces is a gradual and man-made disaster. Climate change is producing higher intensity storms more frequently. At her home rain gauges in Youngsville, Granger clocked 26.5 inches over a month between April and May, just under half the Lafayette area’s average annual rainfall. Porous farmland that held water has been replaced by acres of parking lots, channeling water quickly from subdivisions sprawled on cheap and flood-prone land. Most of the parish flood zones radiate from coulees, not the river.

FEMA's 2018 flood insurance rate map for Lafayette Parish. Areas in dark green represent 100-year flood plains. Source: Lafayette Consolidated Government

Flooding is linked to urbanization. Dredge the Vermilion itself has waved that flag, raising deep concerns about development along Coulee Ile Des Cannes near Scott, which UL’s hydraulic modeling shows is a major factor in flooding.

Dave Dixon, who, along with Sierra Club leader Harold Schoeffler, heads Dredge the Vermilion, says there’s still much to learn about what impact dredging would have. Dredge the Vermilion still views the project as a keystone piece of a watershed strategy but has offered several other strategies up and down the Vermilion and its tributaries.

“It’s one big project. I say it’s the big kahuna because of the money. Is it the big kahuna as in having the most impact? Well, I don’t know yet. We’ll need some more science,” Dixon says. Dredge the Vermilion is in the process of considering a rebrand, Dixon notes, to communicate the group’s broader scope of advocacy.

Cost-benefit analysis informed the Corps’ original decision to shelve dredging the Vermilion as a flood mitigation strategy. The Corps report shows that dredging the river from Vermilion Bay all the way to the river’s headwaters would cost between $100 million and $150 million and achieve the biggest — albeit still relatively marginal — benefit, potentially saving some 250 structures from flooding in a 2016 storm. Dredging less yields less benefit.

Granger argues the Corps/UL modeling overlooks smaller-scale benefits. And her accounting of what her model will show suggests a qualitative view of how benefit is defined.

“Someone may say, ‘There's no cost-benefit,’ and some of the federal ways you do cost-benefit are very structurally related,” Granger says, noting her home flooded in 2016. “But us as residents or people who are business owners or people whose lives are turned upside down, that doesn't fit into a simple mathematical equation with regards to structural damage.”

But the Corps’ mission here is not to alleviate anxiety; it’s to maintain a boatway. Acknowledging that the Vermilion is hardly a commercial corridor, Boyett says the Corps’ operating mission is “safe navigability.” The Corps has also funded navigation projects on other small bayous. And it was on that basis that the agency last dredged one mile of the river in the 1990s.

Typically, the Corps dredges from south to north, meaning Vermilion Parish will play a big role in how this gets done. Most of the $50 million assigned by the Corps is there to account for what’s expected to be a nasty project, Higgins says. The spoil at the bottom of the river is believed to be loaded with dormant toxic materials — seepage of oil and gas from drowned cars, industrial runoff and all kinds of brew.

Officials from Vermilion and Lafayette parishes convened last week to discuss a bottleneck caused by a bridge in Abbeville. Vermilion officials reiterated their standing concern about the potential impact of dredging on their community. They’re at the table, Vermilion Parish President Dane Hebert says, and they believe a workable solution is out there.

This all feels very familiar. What’s changed, to the extent anything has, is not the science of dredging but the justification. The Corps will dredge to clear the river for boats, not flood water. However helpful it is as a flood-reduction strategy is, federally speaking, lagniappe — just as it would have been in 1940.