Project Description

Kilmarnock Stream Restoration & Severe Gully Erosion Remediation

Restoration Need

Many sites within the Town of Kilmarnock were developed prior to consideration of stormwater runoff and its negative effects on water quality. To address the issue, the Town started implementing strategies identified in the Watershed Assessment Report. The eroded gullies in Kilmarnock were washing an extreme amount of sand and silt into downstream floodplains, wetlands, and streams. In addition, both private and public infrastructure and property were at risk of damage or had already been damaged. Based upon four monumented cross sections located in riffle/run sections, the project reach was generally classified as F and G stream channels.

Design Solution

The design approach employed empirical and analytic methods to assess existing and proposed stream morphology and hydraulic processes to provide a stream geometry that will maintain a dynamic equilibrium given the watershed inputs. Design constraints included the stream hydrology, existing trees, geology, upstream/downstream grade control, and valley slope.  These parameters were used as inputs for analysis and influenced design decisions.  The alignment was heavily influenced by the valley slope and the existing trees. Due to the steep valley and stream slopes (>3%), a step-pool morphology was considered appropriate.  This design incorporated alternating larger rock material steps or cascades and the subsequent scour of a pool. A native planting plan was developed for the riparian zone and stream banks.

The project was made possible through a collaborative effort between Ecosystem Services (ES), the Center for Watershed Protection (CWP), and the Town of Kilmarnock and funding from the National Fish and Wildlife Foundation and DEQ. The project was the recipient of the Governor’s Environmental Excellence Award in 2018. The project sites are actively used outdoor classroom for local environmental educators. Lancaster County Middle School participates with the project adjacent to their school as an outdoor lab for science classes.

Goals

  • Reduction in nutrients and sediment
  • Increased retention and infiltration of stormwater runoff
  • Create outdoor classroom
  • Promote collaborative partnership for water quality improvement

Services: Plan Production and Mapping