The King’s Branch Mitigation Site

An Example of On-Site Mitigation

Project Overview

The road project involved widening S-62 (College Park Road) – from US 17A to approximately 500 feet South of Savannah Road – to five lanes for a total distance of 3.8 miles, impacting a total of 0.467 acre of waters, including 0.217 acre of wetlands (0.196 acre cut/fill and 0.021 acre mechanized land clearing) and 943 linear feet (0.25 acre) of tributaries. As the project was not located within the service area of any approved stream mitigation banks or in-lieu fee programs, an on-site, in-kind mitigation within the same watershed as the proposed impacts was approved.

The mitigation site is approximately five (5) miles east of Summerville in Berkeley County South Carolina and is located immediately adjacent to the existing College Park Road and converges with King's Branch approximately 0.75 miles downstream. The site consists of approximately 4.0 acres of land within the SCDOT Right-of-Way along College Park Road.

The mitigation work was begun in 2014 and completed in January 2015.

King's Branch site
Mitigation proposal for King's Branch site

Project Goals

The primary goal of this stream restoration project was to relocate the headwaters of the unnamed tributary (UT) to King's Branch to a position outside of the footprint of the proposed alignment of College Park Road. Restoration goals included reducing sediment loads from channel banks, reducing stressors on water quality, providing/enhancing flood attenuation, and restoring and enhancing aquatic and riparian habitat for flora and fauna typically associated with riparian corridors within the Mid-Atlantic Coastal Plain Eco-region. These goals were accomplished through the following objectives:

  • Relocating the UT using Natural Channel Design principals to a position outside of the fill limits of the proposed location of College Park Road;
  • Restoring a stable dimension, pattern and profile to the UT to promote stabilization of channel banks and bed form;
  • Stabilizing channel-side slopes by planting live stakes, bare roots and native grasses along the channel banks to promote root growth;
  • Enhancing the site's capacity to mitigate flood flows (which could also reduce nutrient export) by excavating a floodplain off of each channel bank;
  • Enhancing in-stream habitat by creating an undulating bed form (ripples/pools) and installing woody structures in the channel to provide shading, natural food sources, and protected areas for propagation. In its pre-mitigation condition the channel had been highly modified and left void of many natural morphological features, such as bed-form and meander diversity, that promote not only stable hydraulics but also diverse aquatic habitats.
  • Promoting more natural valley/floodway flows by removing one existing culvert during channel restoration to lessen backwater during high flow events. Additionally, removing the existing culvert lessened the permanent shading effects on the channel;
  • Planting vegetation along the channel banks and within the riparian buffer to promote natural shading and provide biomass to enhance cover, forage opportunities, and propagation potential of terrestrial and aquatic fauna;
  • Planting native grasses and woody vegetation to mimic the climax buffer community that the site connects to upstream at the beginnings of the restoration reach. Restoring this buffer and connecting it with the mature buffer upstream provide a substantial wildlife corridor through a highly dissected urban landscape. The connected buffers expand foraging and propagation habitats for several terrestrial and amphibious fauna. Restoring the riparian buffer could also reduce the amount of sediment and nutrients entering the stream from adjacent, regularly maintained residential yards and roadways.

Mitigation Types and Amounts

Mitigation Type Stream
Restoration 1,584 feet
Riparian Buffers 3.5 acres
Total Easement Acreage 4.0 acres
Lynches River site
The King's Branch mitigation site during construction