Stream Corridor Restoration

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Information

What is stream corridor restoration?

Stream corridor restoration is one of many ways to restore and manage streams to lower the effects that stormwater has on natural resources in our urban watersheds. Stream corridor restoration works with other stormwater management practices to reduce erosion of streams and flooding. It improves water quality and provides healthy habitats that support wildlife. Local governments design stream corridor restoration projects to support human infrastructure like buildings, roads, and power systems. They also design projects with a focus on public health and safety. 

The goals of stream corridor restoration projects vary based on a study of current conditions. The study finds limits and opportunities based on how we use the land now and expect to use it in the future. Stream corridor restoration rebuilds the shape and structure of the stream. The designs restore habitat and native, aquatic species that help the stream return to its natural function and work in a sustainable way. It is important to remember that natural streams in the urban environment of Northern Virginia may look very different than natural streams in other areas. 

As water flows, it wears down the stream bottom which makes the stream grow deeper and the sides of the stream grow taller. When the stream becomes very deep and the sides become very tall, the deeply incised stream channel is unable to do its job correctly. Local governments rebuild deeply incised stream channels to carry water and sediment in a sustainable way that supports stream function. They give the stream a gentle slope to connect the stream to the neighboring low-lying ground called the floodplain. This creates stable stream banks that provide habitat for native plants. 

There are several different approaches to accomplish stream corridor restoration projects. The Natural Channel Design approach models construction from the natural shape of the stream, the nearby floodplain, and the trees and plants along the stream. The Regenerative Stream Channel approach uses barriers in the stream to create more connectivity with the floodplain during smaller rain events. The Legacy Sediment Removal approach removes sediment that has built up in the stream over many years, which restores the natural state of the stream and its resources.

Oakford

Why do local governments do stream corridor restoration?

Population growth in the past several decades led to a fast change in the way we use our land. The impacts to our local streams in Northern Virginia are the result of changes in land use from forest, to agriculture, to the current urban communities. This makes our waters and natural resources a part of the surrounding developed lands. Changes in the way we use land and the way we manage it effects the overall health of our streams over time. 

When we build roads, buildings, and parking lots, we create more hard surfaces that water cannot soak into. This causes more water to runoff into streams in a short period of time instead of gradually soaking into the land. Large amounts of polluted stormwater overwhelm our streams during rain events which can wear down stream banks. This can also cause streams to disconnect from groundwater and adjacent floodplains. This forces streams to grow deeper and wider, exposing tree roots and systems such as sanitary sewer and stormwater pipes. 

The Virginia Department of Environmental Quality (DEQ) and localities monitor the biological, chemical, and physical health of our local streams. Virginia DEQ listed approximately 250 miles of streams in Northern Virginia that are impaired in 2018. This means they are too polluted or degraded to meet the water quality standards set in the Clean Water Act. Many of these streams are unable to support healthy fish, aquatic insects, swimming, boating, edible fish or shellfish, or safe drinking water. Local governments do stream corridor restoration along with stormwater management to help spread out the stream’s energy to slow it down. This reduces flooding further down the stream and returns the stream to a long-term healthy state while protecting property and infrastructure from damage.

What are the benefits of stream corridor restoration?

The benefits of stream corridor restoration go far beyond stable stream banks, reducing erosion, and reducing sediment pollution. Reducing erosion improves the water quality of local streams making them a better habitat for fish and aquatic bugs. Stream corridor restoration projects can improve the connectivity of streams with groundwater. This creates conditions that allow the stream to function more naturally, moving sediment in a way that does not erode the stream during small storm events. 

Widening streams may cause property damage to nearby homes and infrastructure and pose a risk to public safety if left untouched. Fixing these streams with stream corridor restoration projects reduces that threat. Additionally, there are opportunities for the repair of  exposed and damaged systems such as sanitary sewer and stormwater pipes during construction of stream corridor restoration projects.

Are there rules we must follow to protect our streams and rivers?

Stream corridor restoration projects need both federal and state level permits to assess all potential effects of a project before it begins. The nationwide permit for Aquatic Habitat Restoration, Establishment, and Enhancement Activities is a requirement to work   within streams, the area along streams, and wetlands. This permit focuses on fixing water habitat to improve water quality and wildlife communities. This includes monitoring the stream before and after construction to measure the success of a project. 

Also, local governments must follow the Municipal Separate Storm Sewer System (MS4) permit to manage stormwater flowing into our local streams. The MS4 permit requires localities to protect and restore streams and their surroundings through policies and regulations. These include land use policy, stormwater regulations, and stormwater improvement projects. 

Total Maximum Daily Loads (TMDLs) are specific requirements under the MS4 permits for the release of stormwater to our local streams. A TMDL is the maximum amount of sediment and pollution that can occur in a body of water to meet water quality standards set by the Clean Water Act. Both the Chesapeake Bay and local rivers and streams require TMDLs if the waters are impaired, meaning they are not fishable and swimmable. Localities create action plans to address TMDLs that consider cost efficiency, addressing major pollution sources, and the chance of success for actions carried out. 

Local governments fund projects including stream corridor restoration and upstream stormwater management practices because they must meet these requirements. Stream corridor restoration projects help jurisdictions reduce nutrient and sediment pollution to an acceptable level. These projects are often the most cost-effective choice to reduce as much pollution as possible per dollar spent.