Nutter & Associates, Inc. compiled a compensatory mitigation plan to offset jurisdictional waters of the U.S. impacted during construction of a fishing pond on a forested tract in south Georgia. The Settlement Agreement included conceptual plans to permanently lower the pool elevation of the pond on the property and restore approximately 1.07 acres of wetlands and 884 linear feet of impacted stream. Reference conditions for both stream morphology and vegetative community assemblages were assessed from an unimpacted stream reach and valley bottom wetland on the property.

Nutter & Associates conducted a bathymetric survey of the pond to determine the presence and magnitude of any topographic modifications of the valley that may have occurred during the construction of the pond. Subsequently, the water level of the pond was significantly drawn down to expose the valley flat throughout most of the upstream portion of the pond, which allowed for traditional surveys of the valley flat and adjacent backslopes. All survey data was vertically corrected to established elevation benchmarks.

Permanent modifications to the outlet structure of the pond reduced the pool elevation by 7.5 feet, thereby reducing the pond’s surface area from approximately 10.3 acres to 5.9 acres. This allowed for the restoration of approximately 525 linear feet of perennial stream, passive restoration of an additional 240 linear feet of intermittent stream, and restoration of approximately 5 acres of valley bottom, including at least 1.1 acres of wetlands. Meanders within the impacted stream reach were relatively few and widely spaced. By restoring meanders and providing the channel access to bankfull benches throughout the restoration reach, a moderately sinuous low-flow channel will form within the broader belt width.

Spoil material deposited on the toe slopes adjacent to the upper reach of the impacted stream during construction of the pond were regraded to effectively build an active floodplain around the channel on the existing valley flat. Topographic surveys of the existing valley backslopes provided the target slope for these graded areas.

A new active floodplain was excavated from the existing valley flat adjacent to the lower reach of the project stream, effectively providing a new active floodplain at a lower elevation than the current valley flat, which is an abandoned terrace that is largely inaccessible to floodwaters carried by the restoration reach. Target dimensions for low-flow channel width, bankfull width, bankfull depth, and size of the benches (both lateral and longitudinal dimensions) were based on similar features surveyed in the reference reach. Benches are designed to permit floodwaters to leave the baseflow channel at bankfull flows on a recurrence interval of approximately 1 to 1.5 years. Channel banks above the benches were graded at 3:1 slopes to meet the existing valley flat. Existing littoral shelves on the perimeter of the pond were regraded as much has possible to match the natural valley topography without adversely affecting existing forest vegetation. Monitoring of the restored streams, riparian zones, and wetlands will take place for five years following the restoration activities as required by USACE guidelines.