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How is Stream Restoration Done?

Stream Restoration Categories

Stream restoration methods can be divided into two main categories:

Functions-Based Restoration - This approach aims to make the stream healthier without changing its shape.
Form-Based Restoration - This approach changes the shape of the stream to better handle storm flows and sediment.

Deciding whether to use a Functions-Based or Form-Based approach depends on several factors, including the project's location, the amount of development around the stream, how much runoff the stream gets, the condition of the forest around the stream, the needs of the people who live nearby, and the project's goals.

Methods to fix damaged stream channels

Fairfax County uses different methods to fix damaged stream channels. Like many places in the mid-Atlantic region, stream restorations here often use Natural Channel Design. This method creates a stable stream channel that can handle heavy storm flows and protect roads, bridges, and other infrastructure without eroding. It effectively reduces sediment and nutrients in the stream and usually needs little to no maintenance when it's built well.

Restoration methods include:

Method	Type
Natural Channel Design	Form-Based
Newbury Riffles	Functions-Based
Regenerative Stormwater Conveyance	Form-Based
Beaverdam Analog	Functions-Based
Stage Zero	Form-Based
Large Woody Debris Jams	Functions-Based

Stream Functions Pyramid, 2012

Stream Functions Pyramid - 1 Hydrology, 2 Hydraulic, 3 Geomorphology, 4 Physicochemical, 5 Biology

The Stream Functions Pyramid is a tool that experts use to understand what happens in streams. They look at how much water flows through the stream and if it's causing erosion. They also check what types of soil and rocks are there, if the water is clean or polluted, and what kinds of animals live there and their habitats. By measuring these things beforehand, they can make a plan to improve the stream and later see if their plan worked.

Functions-Based Restoration

Accotink Creek @ Wakefield Park Stream Restoration

Project Overview:

Project uses 4 Newbury Riffles to stabilize about 1 mile of stream
Significantly lower tree loss and land disturbance
Preservation of good quality habitat both in stream and floodplain
Much lower project costs

Accotink Creek @ Wakefield Park Stream Restoration map showing Newbury Riffles.
Click image to enlarge.

Form-Based Restoration

Natural Channel Design: Crook Branch @ Mantua Elementary School Stream Restoration

Changing the stream’s form often requires more room to create a stable meandering channel and more potential tree loss.

Rosgen priority level 1 restoration approach. Plan View. Existing Incised Channel. Flow. Cross Section. Restored Channel. Step-Pools. Wetlands. Source: Natural Channel Design Review Checklist, Stream Mechanics and US Fish & Wildlife Service

Crook Branch at Mantua Elementary School, Annandale, VA Before 2021 and After 2023

Crook Branch @ Mantua Elementary School Before — Crook Branch @ Mantua Elementary School before restoration

Crook Branch @ Mantua Elementary School after restoration

Stage Zero and Beaver Dam Analogs

Two stream restoration methods that have become popular in recent years are Stage Zero and Beaver Dam Analogs. These methods can offer great benefits but have specific requirements and can't be used everywhere.

Stage Zero is a form-based restoration method that often requires significant changes to the floodplain to create a diverse wetland complex. The benefits include restoring wetlands, reducing flood impact, and significantly reducing pollutants. However, the major impact on trees and the creation of wetlands near homes can make it challenging to use in urban areas.
Beaver Dam Analogs are a functions-based restoration approach that uses a series of engineered wood and earthen blockages, similar to those built by beavers. The benefits can include lower overall construction impacts and reduced costs. However, this method requires the removal of about 25% of the trees and is usually only effective where stormwater flows are less intense, the stream valleys are gently sloped, and there is a floodplain that can hold water during storm events.

“Stage Zero” Form-based stream valley restoration – Anne Arundel County, MD - photo by C. Smith — “Stage Zero” Form-based stream valley restoration – Anne Arundel County, MD
- photo by C. Smith

Beaver Dam Analog (BDA) Functions-based restoration - Bacon Ridge, Anne Arundel Co, MD Restoration by Biohabitats — Beaver Dam Analog (BDA) Functions-based restoration - Bacon Ridge, Anne Arundel Co, MD
Restoration by Biohabitats

Reduce Impacts and Improve Ecosystems

Stream restoration often involves construction work that can remove or damage trees and cause a lot of disruption in areas near the stream. To reduce these impacts and improve the ecosystems in the stream valleys, we have developed several methods to assess and restore natural resources.

We inventory all plant communities and focus work in poor quality areas and avoid good ones.
Restoration design with native plant species and careful inspections for quality and installation.
Poor quality plants are rejected.
Control invasive plant species before, during and after restoration.
Monitoring and maintenance of restoration sites for three years.

Public Works and Environmental Services

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Department Resources

Related Resources

How is Stream Restoration Done?

Stream Restoration Categories

Methods to fix damaged stream channels

Stream Functions Pyramid, 2012

Functions-Based Restoration

Accotink Creek @ Wakefield Park Stream Restoration

Form-Based Restoration

Natural Channel Design: Crook Branch @ Mantua Elementary School Stream Restoration

Combination Function/Form-Based Restoration

Flatlick Branch Phase III Chantilly, VA

Stage Zero and Beaver Dam Analogs

Reduce Impacts and Improve Ecosystems

More About Stream Restoration

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