Prior to the establishment of the 1970 federal Clean Water Act, communities, such as Alexandria, allowed streams to be paved over and shifted to make room for development. Streams served as the major way to move sanitary waste out of communities and into the river and serve as a stormwater “pipe” to quickly get stormwater out of our communities during storm events.
Today, the City has a robust sanitary and storm sewer system that constantly operates to move our waste and water which reduces the burden on our local streams. However, the impacts of our past still play a part in the streams we see today. You can easily identify streams that have been worn over time by their severely eroding banks, excess trash and debris, vegetation issues such as undermined trees, exposed rootballs, dead and decaying trees, an abundance of invasive plants or lack of vegetation, and excess silt built up on the stream bed. Stream restorations techniques have evolved over time and currently focus on comprehensive natural channel design that addresses the long-term health and vitality of the stream and its ecosystem.
To learn more about natural channel design, click here to watch Elbow Creek: a Case Study in Natural Channel Design.
Click here to be directed to the Stormwater Infrastructure Projects web page to learn about Lucky Run, Taylor Run, and Strawberry Run stream restorations.
“Stream restoration” is a very broad term that can be as little as removing blockages within systems (a destructive log jam or human generated trash) to redesigning and restructuring a stream within its floodplain. Stream degradation from increased hard surfaces ("impervious surfaces") like sidewalks, roads, etc., in the watershed is often a byproduct of urbanization that negatively impacts water quality. The channel size and flow of a stream is directly related to the watershed that drains into the stream. The size of the watershed, the landuse, and soils are some of the determining factors. Increased volume and velocities of stormwater runoff due to increased hard surfaces may lead to channel erosion, channel incision, and streambank undercutting. Obstructions such as downed trees and dumped materials (trash, concrete, etc) may also impede stream flow. Stream Restoration is one way that developed areas can increase their water quality and improve natural habitat for wildlife and residents.
The Northern Virginia Regional Commission (NVRC) developed a Stream Corridor Restoration fact sheet in June 2020. The 9-page PDF document provides details on stream corridor restorations and provides answers to frequently asked questions such as why do local governments do stream corridor restoration and why don’t we let the stream heal itself naturally. NVRC also developed a Northern Virginia Stream Corridor Restoration Virtual Tour (external link) story map. The map will be updated with our stream corridor restoration projects in Alexandria.
The basic goal of almost all stream restorations is to improve the health of the system. The benefits are many, and which benefits result is largely dependent upon the methods or activities that lead to restoration. Among the benefits are increased dissolved oxygen within the water (better for fish and other critters), increased habitat for aquatic organisms, decreased erosion and thus reduced sediment transport, increased water quality, decreased maintenance activities and more efficient flow through the system. The City of Alexandria is fortunate in that stream restoration is one of the tools available through the Chesapeake Bay Program to meet state and federal mandates to clean up the Chesapeake Bay.
City streams suffer increased flows with elevated velocities when urbanization occurs. These increased velocities result in erosion of the banks and beds of the stream and negatively impact water quality and stream aesthetics.
Stream Assessment Study
The City previously completed Phases I and II of the Stream Assessment Program. Phase I of the program was completed in 2004 and involved the identification and mapping of perennial and intermittent streams, defining the intermittent/ephemeral stream interface and approximate limits of ephemeral streams. Phase II of the program was completed in 2008 and involved the assessment of fifty-seven stream reaches within the City’s eight local watersheds. Information related to stream conditions was collected relating to habitat, infrastructure impacts, problem areas, stream characteristics, and geomorphic classification. The information from these studies will continue to be used to prioritize streams for restoration.
Phase III of the stream assessment studies was completed in February 2019 (click here for report and here for the stream assessment ranking matrix) and provided a prioritized list of stream restoration projects. The scope of work included assessing, evaluating, and ranking five potential project sites using a decision matrix with a comprehensive list of criteria to prioritize the projects. The two top ranking projects were segments along Strawberry Run and Taylor Run. Conceptual designs were developed for these two highest-ranking potential project sites. The Strawberry Run and Taylor Run Stream Restoration projects are currently in progress and additional information can be found on the Stormwater Infrastructure Projects web page.
- Community Meeting - December 5, 2018
Phase III Stream Assessment Study: Potential Stream Restoration Projects
7:00 pm at Douglas MacArthur Elementary School Library
Lucky Run is a tributary to Four Mile Run and part of the larger Potomac River watershed. The Lucky Run watershed consists of approximately 225 acres of densely developed urban land and as a result, the stream currently exhibits instability along with several unfavorable characteristics. The project section of the Lucky Run begins where the stream emerges from the culvert under West Braddock Road near I-395 and continues downstream to the wet pond near Ford Avenue and Park Center Drive. Natural channel design techniques will be applied to approximately 950 linear feet of stream to restore Lucky Run to a stable condition and improve stream function, water quality, and habitat. Additional information can be found on the Stormwater Infrastructure web page.
Taylor Run Stream Restoration
The Taylor Run Stream Restoration project involves approximately 1,900 linear feet section of stream near the Chinquapin Recreation Center and along the walking path in Chinquapin Park and Forest Park. The project limits are from the culvert on the Chinquapin Recreation Center property downstream to behind the First Baptist Church property. The stream corridor is highly disturbed with severe erosion in various locations along the stream with evidence of downcutting and widening at various locations. Significant amounts of fallen trees, riprap, and debris can be found in the channel.
In keeping with the its dedication to improve water quality in the Chesapeake Bay, the City is proposing to use environmentally conscious engineering practices that mimic nature to reconstruct stream banks, encourage native plant growth, and moderate/diminish the impact of streamflow during high-precipitation events. Restoration will reestablish a more stable condition for the stream and improve water quality. Whenever possible, on-site materials will be used in the construction of the project. The project stakeholder team for the City’s stream restoration projects include Transportation and Environmental Services (T&ES), Department of Project Implementation (DPI), Recreation, Parks, and Cultural Activities (RPCA) Natural Resources, the consulting team, and the community. Additional information can be found on the Stormwater Infrastructure web page and the Taylor Run Stream Restoration web page.
Strawberry Run Restoration - Phase II
The Strawberry Run Stream Restoration project involves approximately 900 linear feet section of stream located west of Fort Williams Parkway, east of Taft Avenue, and north of Duke Street. The project limits are approximately 500 feet north of Duke Street and continuing north (upstream) to the culvert under Fort Williams Parkway. Ongoing erosion along the stream banks is deteriorating water quality and threatening existing infrastructure. In keeping with the its dedication to improve water quality in the Chesapeake Bay, the City is proposing to use environmentally conscious engineering practices that mimic nature to reconstruct stream banks, encourage native plant growth, and moderate/diminish the impact of streamflow during high-precipitation events. The restored stream will be reconnected to the floodplain which will help filter pollutants, such as nitrogen, phosphorous, and sediment. The project's main goals include returning Strawberry Run to a more stable condition and restoring the area as an open space amenity. Whenever possible, on-site materials will be used in the construction of the project. The project stakeholder team for the City’s stream restoration projects include Transportation and Environmental Services (T&ES), Department of Project Implementation (DPI), Recreation, Parks, and Cultural Activities (RPCA) Natural Resources, the consulting team, and the community. Additional information can be found on the Stormwater Infrastructure web page.
Strawberry Run Restoration - Phase I
The Strawberry Run project completed in 2010 is located just north of Duke Street for approximately 600 linear feet upstream towards Fort Williams Parkway. Strawberry Run suffered from high velocities as evidenced by the down-cutting creating the vertical side banks and depressed stream bed. There was also a considerable amount of concrete and other debris in the stream creating erosive forces that was removed. The potential new Strawberry Run restoration project discussed above would be situated just north of the previous Strawberry Run Stream Restoration that was completed in 2010.
The philosophy of this particular stream restoration was to reconnect the stream with the floodplain and attempt to maintain the sinuosity (the amount of curve in the stream) so as create as great of variety of habitat within the stream and riparian area as possible. This involved adding cross vanes to roll the water away from the banks centering the flow, control the change in hydraulic grade line, and prevent down-cutting of the channel. J-hooks were added to direct erosive flows away from the streambank, center the flow, and provide scour pools for fish habitat. Other components of natural channel employed were using jute matting to stabilize toe and bank slopes – anchored with a variety of pins and willow stakes at the toe. Willow stakes serve to anchor the matting but moreover to provide a network of natural root systems to anchor the banks in place against erosive flows.
Before Picture After Picture
Download the Strawberry Run Restoration presentation.
The Chambliss Crossing project along Holmes Run near the Dora Kelly Nature Park incorporated stream restoration and a multi-use stream crossing across Holmes Run. The engineering and design analysis explored alternatives for a crossing and stream bank restoration for the banks between North Chambliss Street and the city limits.
The Design was exceedingly sensitive to community desires and the process engaged the local community.
- No rise in water surface elevation
- Maintained as much of the meadow as possible
- Updated the findings of an existing 2002 site/feasibility study for the Holmes Run Multi-Use Crossing with particular consideration paid to recent flood events
- Included hydrology and hydraulic analysis at a preliminary crossing location to identify and propose stream bank stabilization and restoration options which should also be incorporated into design and construction plans
- Included all environmental assessments and environmental impact statements
- Completed design for a crossing and shared-use path connections to existing trails
- Incorporated streambank stabilization/restoration for the banks between North Chambliss and the city line