Stream Restoration Dreams: Stage Zero

Stage 0 restoration at the downstream end of Bacon Ridge Branch at Elks Camp Barrett in Annapolis, MD. Construction completed by Biohabitats.

Matthew Schley/NPS

By NCA Hydrologist Matthew Schley

Slow it down and spread it out. It’s practically a mantra of modern stream restoration. When trying to prevent or repair erosion and channelization, the energy of a stream needs to be dissipated. Due to the limits of infrastructure and property in the National Capital Area (NCA), that energy dissipation often takes the form of boulders and step-pools in the channel that drop water over and around large obstacles. Only larger storm events then fill the adjacent floodplain, preventing increases in flooding to nearby property.

Milk House Ford and Broad Branch in Rock Creek Park, Spring House Run at the National Arboretum, and Alger Park in Washington, DC are just a few regional examples of such ex-stream (pun intended!) makeovers. But as transformative and highly effective as they are, these restorations would be considered Stage 1 restorations where there is still a single stream channel conveying most of the flow. There is an even more radical restoration concept that in urban areas could be considered entirely idealistic: stage zero stream restoration.

Basics

The term “Stage 0” is in reference to the idea of life stages of a stream channel, as proposed in stream evolution models such as Simon and Hupp (1986) and Cluer and Thorne (2013). Stage 0 refers to a pre-channelization phase in which a stream valley is occupied by a forested wetland complex with many anabranching (interweaving) channels. In these stream evolution models, channelization, or the development of a single stream channel that transports the majority of water through the stream valley, occurs in Stage 1 and is the result of a change in the supply or concentration of water in the stream valley. In a highly-developed watershed like many of those found around DC, Maryland, and Virginia, it is often argued that channelization was a direct result of colonization and the initial alteration of the landscape to accommodate both agriculture and settlement.

Channelization continues to worsen across the NCA due to the installation of new impervious surfaces (that don’t allow water to pass through) such as roads, sidewalks, and buildings; the installation of stormwater drainage such as curbs/gutters, stormdrains, pipes, and culverts; and the increase in frequency of large/intense storm events across the NCA in response to global climate change (USGCRP, 2014). As mentioned before, many stream restoration techniques seek to safely pass this increased volume of water through a properly sized channel and floodplain system in which the single channel transports all water for smaller storm events, and the floodplain becomes active during larger storm events. Stage 0 restoration, however, utilizes a different approach.

In Stage 0 restoration, the existing stream channel is essentially filled in so that it is flush with the existing floodplain. In this scenario, the smallest storm events, and even the stream baseflow (the flow that is always occurring, rain or shine) spread out across the floodplain and flow through multiple channels. Stage 0 restoration carries many benefits for the stream valley and the organisms found there. First, the distribution of flows across multiple channels and a wide floodplain reduces the energy of the flow at any given point in the valley. If the flow does not carry excess energy, it is less capable of moving large amounts of sediment downstream, preventing excess sediment and nutrient pollution from ultimately reaching the Chesapeake Bay. Second, the distribution of flows across multiple channels and a wide floodplain creates a wide variety of habitats for both aquatic and terrestrial organisms. The topography of the stream valley is highly variable, with many small mounds and depressions. These create natural high points and pools during flow events which can provide homes to mammals, fish, macroinvertebrates (stream bugs), and others. Finally, Stage 0 restoration is often a relatively low-cost and low-impact approach to stream restoration. Heavy machinery is utilized to bring dirt fill and streambed material into the stream valley, however there is little to no manipulation of the floodplain and little to no use of large stones, thereby reducing both costs and impacts. Trees are often cut down or knocked over to provide habitat and friction (slows down the flow of water) in the stream valley, however these trees are often not lowland/floodplain species and are therefore not likely to survive the increase in flooding associated with Stage 0 restoration.

National Capital Region Streams

Stage 0 stream restoration and its ideas may have a future in NCA parks. It is important however to note that Stage 0 is not a viable approach in all locations. Because water is spread out across the entire stream valley, it is important that there is not an increase in risk to local infrastructure (sewer and water pipes, roads, etc.) or to local property owners. And, allowing a significant amount of water to flow across the floodplain could lead to issues with floodplain erosion, so it is critical to ensure that the stream valley provides the necessary combination of large width and low slope needed to prevent the mass movement of sediment. As such, Stage 0 is most likely to be utilized in parks with fewer infrastructure and human constraints such as portions of Antietam, Monocacy, or Prince William.

To learn more about hydrology and stream restoration in NCA parks, visit https://www.nps.gov/orgs/1027/hydrology.htm.

References:

• Cluer, B. and C. Thorne (2014). “A stream evolution model integrating habitat and ecosystem benefits.” River Research and Applications, 30, 135-154.
• Simon A, Hupp CR. (1986). “Geomorphic and vegetative recovery processes along modified Tennessee streams: an interdisciplinary approach to disturbed fluvial systems.” Forest Hydrology and Watershed Management. IAHS-AISH Publ.167.
• USGCRP (2014). Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman, A. Whelchel, D. Wolfe, and F. Lipschultz, 2014: Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.