A Whole-System Approach for Restoring the Wetlands of the Western Lake Pontchartrain Basin

G. Shaffer

Project Overview

(click for larger image of habitat classification map)

Most of the Maurepas swamp appears to be converting to marsh and open water primarily due to the lack of riverine input. In attempt to redress the degraded state of these wetlands, a diversion of Mississippi River water into the swamps has been proposed and is currently being engineered. While this diversion is likely to greatly benefit the wetlands that it influences, this influence is primarily limited to the southern and southwestern portion of the swamp.

What is needed is a system-wide approach that considers restoration measures that will enhance conditions in the wetlands north and northeast of Blind River. Specifically, we conducted a feasibility analysis on gapping the Amite River Diversion Canal to increase hydrologic exchange with the adjacent swamp, and re-introducing Mississippi River water to potential sources in the northwestern portion of the study area, such as Bayou Manchac, Fountain Bayou, and New River.

The feasibility study on gapping the Amite River Diversion Canal to increase exchange with the adjacent swamp indicates that the gaps should not be equidistantly located, as originally proposed.  The area north of the Diversion Canal near Blind River is severely impounded with approximately 2.2’ of nutrient-poor, stagnant water.  Swamp is converting to floating marsh in this area and it compares with the most degraded areas in our extensive data base.  Conversely, the areas south of the Diversion Canal and north near Petite Amite River approach the healthier sites in the data base, such as those along Hope Canal.  A single 40’ bridge gap to the southern area and gapping the degraded spoil banks of the Petite Amite in the northwestern area would further enhance primary and secondary production.  A series of 40’ bridge gaps would provide extensive exchange to the degraded swamps contiguous with the Diversion Canal and would require far less operation and maintenance efforts.

 Satellite Imagery and Habitat Classification:  The vast majority of the Maurepas swamp will not regenerate if logged.  Our habitat classification map has been presented to the Governor of Louisiana (Chambers et al. 2005) and has been used in the Comprehensive Habitat Management Plans of The Nature Conservancy and the Lake Pontchartrain Basin Foundation.  It also has been used, as part of the Science Working Group’s report (Chambers et al. 2005), by EPA to deny a permit request (of Steve Buratt) to log 200 acres of the Maurepas swamp.  In addition, we use the image herein to provide evidence that Neotropical birds prefer swamp and largely avoid marsh.  Unfortunately, large portions of swamp have converted to marsh over the past 50 years (red areas in Figure 1) and most of the remaining swamp is on this trajectory.  A Mississippi River re-introduction at Hope Canal and gapping the Amite River Diversion Canal are two projects that may reverse the trend of swamp loss.  Without these restoration projects, most of the Maurepas swamp will be lost within the next several decades.