by McKenzi Heger | January 11, 2019
Stream restoration is more than just stabilizing and repairing stream channels, it also revitalizes and protects the health of our watersheds and aquatic ecosystems. Described as “a set of activities that help improve the environmental health of a river or stream”, stream restoration seeks to stabilize channels within their present environmental context, and can seek to accomplish goals like reducing erosion of channel beds and banks, and reducing downstream sedimentation. In all cases, a set of site-specific goals and objectives are developed and then implemented. These are focused on restoring function and value, which protects aquatic life and the health of our aquatic systems.
The process of restoring a stream varies depending upon the nature of the impairments, site-specific constraints, and goals of the project. Goals range from supporting recreational activities within the stream corridor, navigation, hydroelectric power, habitat improvement for wildlife, and more. Many techniques seek to use natural materials like wood, rock, and cobble. Some examples of restorative techniques and applications are:
- Cross-vanes — To reduce erosion to the stream banks, stones are placed across the stream in the shape of a C or V to guide the water into the center of the channel and away from the channel banks.
- Step pools — The stream bed is stepped down in elevation. Typically rocks are placed in a series of rows that mimic stairs, creating small pools of water between each “stair”. This technique is used to stabilize a stream with a steep slope while the pools dissipate the energy from high flows and provide habitat for aquatic life.
- Brush layering — Live branches are layered and attached to the stream bank. The branches protect the bank from erosion and will root and grow along the bank over time. This will provide even greater bank protection as the plants hold down the soil with their roots.
- Log vane — To keep a stream bank from further eroding, logs are securely placed to redirect fast-moving water away from one bank and into the center of the stream. The logs provide additional benefits to the ecosystem by providing an aquatic habitat.
- Grading and planting — Stream banks are graded, or shaped, from steep angles to lower, more stable angles, or in some locations a series of steps known as floodplain benches. During high stream flows, the lower bank angle and benches will give the stream more room to flow, reducing the forces on the stream banks. In order to protect the banks, plants are planted along the bank to help hold the soil in place with their mature roots.
- Planting — Along the stream, plants are planted to control erosion of the stream bank by keeping the soil in place with their roots. The stems of woody plants also help reduce the energy from stream flows along the banks, providing additional bank protection and ultimately provide shading for temperature control and a source of wood and biomass input to the stream.
- Woody debris — Logs and other woody material on the side of the stream bank or extending into the stream channel have several benefits. Depending on where the woody debris is placed, it can reduce erosion by acting as a buffer to a stream bank. Additionally, woody debris of various sizes, from small branches to large logs, can provide habitat for a variety of aquatic life.
GreenVest seeks to generate holistic restoration projects by assembling and implementing large-scale projects. These large-scale projects tend to yield greater ecosystem benefits and have a higher probability of achieving self-maintenance. Currently, GreenVest is in the process of completing the design and approval of over 15 miles of stream restoration across the state of Maryland. The 15 miles of restoration will take place on five different sites and across four counties (from the Piedmont to the Coastal Plain), with the largest being over 5.5 miles long. The result will be significant water quality and habitat improvements for the Chesapeake Bay Watershed. Construction will commence on these five projects during the spring of 2019.
As with many of our projects, stream restoration requires diligent monitoring to ensure that these systems reach self-maintaining equilibrium. To learn more, contact us today.