Wetland Mitigation Banks and the No-Net-Loss Requirement: An Evaluation of the Section 404 Permit Program in Southeast Louisiana

• Main Author: Tyrna, Abbey Anne
• Other Authors: R. Eugene Turner
• Format: Others
• Language: en
• Published: LSU 2008
• Subjects: Environmental Studies
• Online Access: http://etd.lsu.edu/docs/available/etd-04102008-141642/

Section 404 of the Clean Water Act provides regulatory oversight for wetland conservation. One goal of the Section 404 program is to achieve a no-net-loss of the remaining wetland acres and functions. Wetland mitigation banks have been incorporated into wetland policy because of their potential advantage in achieving the no-net-loss requirements. This study analyzed four wetland mitigation banks with credits sold between 1991 and 2007 in southeastern Louisiana to determine if they were contributing to the goal of no-net-loss. The goal of no-net-loss is reached when there is complete compensation of wetland structure and function. The study area for this research was Liberty Bayou-Tchefuncta Basin, USGS Cataloging Number 0809020. A structural comparison between bank wetlands and those permitted was made using data collected from permits and from authoritative bank documents on wetland size and vegetation. A functional assessment of the wetlands was conducted through hydrogeomorphic classification using a geographical information system to integrate information on their geology, ecoregion, slope, and soils. Wetland functional performance was calculated using wetland habitat quality and mitigation ratios as variables. The results from the permit data showed that 2,546 acres (850 ha) of mitigation was required to replace 2,309 acres (932 ha) of impacted wetlands, creating an additional 238 acres (96 ha) of required mitigation. Ninety-five percent of the wetlands lost were replaced with wetlands that had similar vegetation. Furthermore, the hydrogeomorphic classification illustrated that 99% of all permitted wetlands were also functionally similar to their mitigated counterparts. The mitigation ratios used to calculate functional performance showed a functional loss of 2,505 acres (1,014 ha). A positive wetland trade is revealed when looking at wetland structure alone. However, the functional assessment indicates a negative functional trade between the permitted wetlands and the mitigated wetlands. The cumulative effect of a loss in wetland functions could be a degraded watershed that provides inferior water quality, habitat quality, water storage capacity, etc. The mitigation requirements were found to be inconsistent leading to a high functional loss for the basin. Permitted impacts under Section 404 could be better managed if a standardized method for calculating mitigation ratios was implemented.