The gist: Dredging the Vermilion is becoming a political movement in Lafayette, driven by the trauma of repeat flooding events since the catastrophic no-name floods of August 2016. Studies continue as engineers and public officials debate the efficacy of digging out the bayou.
“Unclogging the Vermilion River is the first step to solving this problem,” said Paul Baker, headmaster of Episcopal School of Acadiana in remarks to the City-Parish Council Tuesday night. Baker’s home along the St. John coulee flooded in 2016 and again during the June 2019 “rain bomb.” He exhorted the council to take action, worrying that officials may shrug off solutions given the magnitude of the problem. “My wife and I live in fear of the rain,” he said, “and that’s not a healthy way to live in South Louisiana.”
Many now credit Dredge the Vermilion activists Harold Schoeffler and Dave Dixon for driving the conversation. Dixon and Schoefller were behind the push to stop pumps north of Lafayette Parish ahead of Tropical Storm Barry, which in part lowered the base level of the bayou when joined by a favorable and powerful north wind. It’s not clear which intervention — man’s or nature’s — did most of the work lowering the river’s level. Regardless, the episode has given the pair a lot of credibility among residents.
Meanwhile, studies and stakeholder meetings continue. The Army Corps of Engineers is studying the Vermilion River before it will commit to dredging the entire bayou through Vermilion Parish. A hydrology and hydraulic study is expected to be completed by December 2019, according to Greg Ellison, an aide to U.S. Rep. Clay Higgins who presented to the council Tuesday.
There is dispute about what impact dredging would have. Some engineers push back against the narrative that lowering the Vermilion would have the impact clamored for by repeated flood victims. Not all flooding in the parish is related to river back flow. Youngsville City Engineer Pam Granger pointed out at a GOP town hall Tuesday night that flooding in the bedroom community is not connected to the Vermilion. Other neighborhoods in Lafayette itself, like Quail Hollow, reportedly would not benefit from river dredging. LCG Public Works Director Mark Dubroc, exasperated, openly questioned whether digging out decades of muddy bottom would do any good.
“All of this conversation is devoid of technical support,” Dubroc said, drawing derisive cackles from the audience. He noted the Corps of Engineers last dredged the river in the mid-90s to restore navigability, not address stormwater management. However, residents along the bayou, including Councilwoman Nanette Cook, claim that dredging effort stopped water from reaching their homes.
Let’s talk detention. Some use of detention/retention — mechanisms of holding stormwater and slowly releasing it into coulees and the river — is expected to be part of whatever strategy is implemented long term. Dubroc said older developments, built before retention was required by local government, are in part responsible for the extra runoff. He said 4,000 to 7,000 acres of retention could be needed to do any good. That’s roughly the size of a square bound by Johnston and Ambassador Caffery, Kaliste Saloom and Pinhook.
Right now, spot dredging is on the table. Pushback from Vermilion Parish and continued studying will delay full dredging. Vermilion Parish officials, also represented in Congress by Higgins’ office, say the move could worsen flooding in the area and cause saltwater to invade the low-lying parish, imperilling seafood commerce. That leaves dredging “hot spots” to be the remaining option within Lafayette Parish. Again, there’s some question whether that approach would deliver the solution desperately wanted by many who live along the bayou.
Ellison said the council could spot dredge now. He relayed conversations with the corps in which officials offered to help LCG get a permit to spot dredge the river. Council members committed to finding the money in the upcoming budget process. Ellison guesstimated that spot dredging could cost $5 million and that LCG could draw the money down out of $1.2 billion in HUD dollars Congressman Higgins helped secure.
Congress has authorized dredging the Vermilion. We reported that last year. That essentially means the money has been allocated but not delivered.
What to watch for: Whether LCG moves forward with an intermediate dredging plan. It’s election season, and political pressure from flooded-over constituents could prevail on local officials to take the step. To be sure, it’s not a sure thing that even spot dredging would make an impact. That would take study. Many residents are tired of studies.
4 Comments
It's not real clear to me that dredging isn't being imagined as somehow a magical solution: if I dig a deeper ditch next to my house but it connects to my neighbor's ditch that remains the same volume, where's the water going to go? (I.e., this assume dredging the entirety of the Vermilion and not just the part that goes through Lafayette.)
Second, just making the Vermilion deeper doesn't make it able to absorb more water, unless we drain it before every rain? Like the example aboe, more water can't go into a full ditch -- this I know from recent rains.
Am I missing something basic about hydrodynamics here?
@John, you are correct that it is not clear that dredging will reduce flood risk, that is why hydraulic/hydrologic/sediment transport studies need to be done. Dredging will undoubtably provide more storage within the channel, but that may be a small amount of additional storage compared to how much water is being delivered to the river given the increase in impervious surfaces and lack of retention/detention in "legacy" parts of the watershed. This is to say nothing about how dredging will affect the bed slope and transport capacity. Rivers like the Vermillion are challenging to manage given the tidal influences in the lower reaches and the low bed slope, so it is all the more important to do in-depth modeling studies before taking any action.
Would increasing storage in the river lead to some flood events having a lower elevation? Probably. Is it enough to keep repeat flooders houses dry? That is harder to say. And given the cost of fully dredging, we need to carefully weigh the benefits, that way we can prioritize our spending and reduce wasted effort.
@John @Brian, I am not an engineer, just one of thousands who flooded in 2016 and one of many who flooded on June 6. We live on St. John's coulee and love our home which had not flooded in the 25 years we've lived there, prior to '16. We are currently investigating ways to protect our home from future events but the options are few and probably not even do-able.
I have been to several meetings concerning dredging and other means of flood alleviation problems in our watershed.I don't feel qualified to get into a back-and-forth about the pros and cons so I reached out to Dave Dixon who has given me permission to post the following response:
"Concerning Mr. Mark Dubroc saying the dredge project will not work, we offer these counter points. Empirical evidence that after 3 major floods in '40, not another major (event) for 60 or so years. Additionally, the residents along the river reported that after dredge work in 98, water quit coming up in their back yards. Additionally, Mark Wingate’s 94 report called for dredging.
Technical discussion below:
Mr. Dubroc claims that river will have laminar flow and only effective flow will be above mean low gulf. If that was true TVFD would not work as salt water is heavier than fresh.
Additionally the hydrostatic head of the water in river with a full bank in Lafayette parish where top bank elevation are 10-14 feet will push the water to locations with lower top bank elevations like Gulf and Cypress Island . Additionally the friction of the flow will drag the whole channel to what ever direction the water is flowing minimizing any laminar flow effects."
The video of the LPC meeting starting with Mr. Dubroc is online at https://www.ustream.tv/recorded/123454377