Officials: Bayou Chene project won’t cause island to flood

The Bayou Chene Flood Control Project shouldn’t cause any flooding on Avoca Island because the island just floods naturally when the Atchafalaya River rises, according to a St. Mary Levee District report.
Levee district officials sent a response Monday to the U.S. Army Corps of Engineers on a report issued by Avoca Island’s landowner regarding the Bayou Chene Flood Control Project’s potential harm to the island. The district also submitted the response to the Louisiana Department of Natural Resources.
Levee District Executive Director Tim Matte emailed the district’s report to The Daily Review.
In May, Senior Permitting Analyst Gregg Fell of Natural Resource Professionals submitted Avoca’s report on the Bayou Chene project’s impact to the Corps and DNR.
The project, which is located on Bayou Chene in Amelia, involves installing a floodgate that can be closed to protect areas in St. Mary, Lower St. Martin, Terrebonne, Assumption, Lafourche and Iberville parishes from flooding. The St. Mary Levee District has not yet received the two required Corps of Engineers’ permits for the Bayou Chene project.
Officials are trying to get the project ready for construction by April 2017 when Restore Act money from the BP oil spill settlement becomes available.
Levee district leaders disagree with Avoca’s assessment that there will be any indirect impacts to Avoca Island in regard to the Bayou Chene Flood Control Project, the district’s report said.
Avoca filed a lawsuit in November 2015 against DNR requesting that the department rescind the Bayou Chene project permit DNR issued in September 2015.
The lawsuit said that DNR didn’t have the information needed to evaluate the project’s impacts and failed to record evidence regarding the project design. A hearing, which could determine the outcome of the lawsuit, is set for Friday in district court, Matte said.
Avoca used modeling to determine how many acres the Bayou Chene project would have affected in 2008, 2009 and 2011, taking the average of those results to arrive at the 371 acres of impact.
Avoca Island floods annually to varying degrees, primarily due to spring high water events in the Mississippi River and Tributaries system in a manner similar to the majority of the land within the Atchafalaya Basin, the levee district’s report stated.
“It is widely known that the duration and extent of the annual flood events are directly related to factors such as the magnitude of the Atchafalaya River discharge, rainfall amounts, tides, and opening of the Morganza Floodway,” district’s report stated.
The district assessed the areas of concern in relation to the 2011 and 2016 flood events when a temporary flood protection structure was put in place on Bayou Chene and concluded that there were no visible impacts to any wetlands, bottomland hardwoods or open pastures within Avoca’s area of concern.
Avoca stated that the 2011 event caused 529 acres of impacts to the island.
“It is clear by comparing the aerial photography from before and after 2011 closure that there have been no vegetative, land or other losses/impacts that could be attributed to the 2011 emergency closure,” levee district officials said.
Avoca’s simulations for 2008 and 2009 with a gate closure is a hypothetical exercise because no such closures occurred in 2008 and 2009, the levee district stated.
Contrary to Avoca’s assertions, the levee district’s report says its model properly calculated changes in water levels on Avoca Island due to annual Atchafalaya River flood.
Modeling shows that the change in peak flood water level in Bayou Chene and on Avoca Island is less than 0.1 feet and 0.6 feet when the gate is open and closed, the district said. Avoca has not documented any detrimental impacts to vegetation in any of their reports to date, the district said.
The levee district maintains that Avoca’s impact acreage assessment is unfounded and should not be considered. During the 2011 and 2016 floods, the emer-gency closure provided immense flood protection benefits to the industry and community in the five-parish area and a permanent structure would provide similar benefits when required in future, the district said.
The Daily Review left a phone message for an Avoca representative but didn’t receive a call back this morning.