The Lynches River Stream & Wetlands Mitigation Site

An Example of Off-Site Mitigation

Project Overview

The Lynches River Stream and Wetlands Mitigation Site is located approximately four miles (4.0) south of Lamar in Darlington county, South Carolina. The site contains the Lynches River and its associated floodplain, Rose Branch (a direct tributary to the Lynches River), an unnamed tributary (UT) to Rose Branch, riparian wetlands within the Lynches River floodplain, and headwater and riparian wetlands associated with the Rose Branch and the UT to the Rose Branch. The site is located within the Southeastern Plains Ecoregion and within the 8-digit hydrologic cataloging unit 3040202. The Lynches River flows into the Pee Dee river approximately 50 miles southeast of the site. The Lynches River, as it flows through the site, is designated as a Scenic State River. It is also listed on the draft 2012 303(d) list for recreational use and fish consumption due to high levels of mercury and fecal coliform bacteria.

Lynches River site
The Lynches River mitigation site

The mitigation work was carried out between August 2013 and May 2014. The mitigation activities are summarized below.

Streams

  • Lynches River — Preserved 19,450 linear feet of the Lynches River and its mature riparian buffer off the left bank. The riparian buffer exceeds 300 feet in width on average.
  • Rose Branch — Preserved 8,665 linear feet of Rose Branch and its mature riparian buffer off both banks. The riparian buffer exceeds 75 feet on average on both banks.
  • Rose Branch — Restored pattern, profile, dimension, and riparian buffer to 3,395 linear feet of Rose Branch. More than half the restored footage was restored to long stretches of a relic channel not filled in when Rose Branch was ditched and rerouted from its natural watershed years ago. The portions of Rose Branch not restored to its relic channel were restored through a then existing pond.
  • Rose Branch — Enhanced 3,200 linear feet of Rose Branch through the floodplain of the Lynches River affected by two separate dirt road dikes. Enhancement was accomplished by complete removal of the downstream dirt road dike and by removal of several sections of the upstream dirt road dike to allow more natural flows down valley.
  • UT to Rose Branch — Restored and pattern, profile, dimension, and riparian buffer to 3,000 linear feet of the UT to Rose Branch that flowed through pasture and agricultural fields, is highly incised, and displays no riparian buffer.
  • UT to Rose Branch — Preserved 685 linear feet of UT to Rose Branch that flowed through a pond before emptying into the Lynches River floodplain.
  • UT to Rose Branch — Preserved 500 linear feet of UT 2 that flowed through an agricultural field. A riparian buffer was planted along both banks of UT1 as part of preservation practices.
  • UT to Rose Branch — Restored and pattern, profile, dimension, and riparian buffer to 470 linear feet of UT to Rose Branch that flowed through a pond before emptying into the Lynches floodplain.
  • UT 1 — Preserved 1950 linear feet of UT 2 that flowed through an agricultural field. A riparian buffer was planted along both banks of UT1 as part of preservation practices.
  • UT 2 — Preserved 1950 linear feet of UT 2 that flowed through an agricultural field. A riparian buffer was planted along both banks of UT1 as part of preservation practices.

Wetlands

  • W1 — Restored hydrology and hydric vegetation and upland buffers to 8.3 acres of W1 by plugging and filling two ditches and planting hydric vegetation.
  • W1 — Enhanced hydrology and hydric vegetation to 3.0 acres of W1 by plugging and filling two ditches and planting hydric vegetation.
  • W2 — Restored hydrology and hydric vegetation to 1.6 acres of W2 by removing a soil road dike that traversed the floodplain of the Lynches River.
  • W2 — Enhanced hydrology through 60.3 acres of W2 by removing one entire soil road dike that traversed the Lynches River floodplain and removing several sections of a second soil road dike that traversed the Lynches River floodplain further up-valley.
  • W2 — Enhanced vegetation and terrestrial habitat by prescribed burn in 100.7 acres of recently clear-cut wetlands within the Lynches River floodplain.
  • W2 — Preserved 250.7 acres of existing mature riparian wetlands within the Lynches River floodplain.
  • W3 a — Preserved 1.3 acres of wetlands and upland buffers associated with the riparian corridors of Rose Branch and UT Rose Branch.
  • W3 b & c — Preseved 3.5 acres of wetlands and upland buffers associated with Rose Branch and an adjacent headwater wetland.
Rose Branch UT before
Preconstruction, UT to Rose Branch
Rose Branch UT after
Post construction, UT to Rose Branch

Mitigation Types and Amounts

Mitigation Type Stream (feet) Wetland (acres)
Restoration  7,135    9.9
Enhancement  3,200 164.0
Preservation 31,430 255.5
Total 41,765 429.4
 
Riparian/Upland Buffers 275 acres 95 acres
Total Easement Acreage 800 acres
Relic creek before
Preconstruction, relic creek
Relic creek after
Post construction, relic creek