Stream Restoration: Helpful or Harmful?

Many of you may have noticed the large scale stream restoration that is occurring in Paint Branch Creek on the backside of campus (Figure 1). A restoration is defined as returning the stream to a close approximation of its pre-disturbed condition. When I see a restoration of this magnitude I wonder is this helping or causing more harm to the stream? Rivers and streams in the United States provide crucial ecosystem services to humans; however our alterations of the natural landscape have become a major threat to stream water quality.  According to a water quality inventory done in 2000 by the Environmental Protection Agency, approximately one-third of U.S. rivers and streams are considered impaired or polluted. Due to this extensive degradation, billions are spent annually on stream restoration efforts.

Figure 1. Restoration efforts in Paint Branch Creek above campus (McDowell, 2012).

The stream restoration occurring off campus appears to involve changing the shape of the stream banks and then anchoring them into place with large boulders. The goal of this type of restoration project is to stabilize the banks to reduce the amount of sediment eroded into the stream environment. Sediment is considered to be one of the major problems effecting water quality in the United States, it can clog streams, limit light reaching stream organisms, and carry toxic pollutants. In this area, our streams drain into the Chesapeake Bay which has problems with excessive suspended sediment (sediment in the water column). This restoration is of importance to me because my master's thesis will involve looking at the suspended sediment in the NE Branch of the Anacostia and Paint Branch in order to determine if this type of restoration is even necessary. I plan to examine the system to see how much sediment is actually being transported and what areas of the stream are acting as sources and sinks for sediment. Another goal of anchoring the banks in a stream restoration is to prevent lateral migration, or movement of the stream left and right, this is important in streams like Paint Branch where construction has occurred so close to the stream. Some parking lots along route 1 had even begun to fall into the stream before the restoration began.

Figure 2. The sediment line showing the merging of Paint Branch Creek and Indian Creek to form the NE Branch of the Anacostia (McDowell, 2012).

You may be wondering how something that stabilizes the banks from erosion and prevents parking lots and building from falling into a stream could be considered anything but good, however I have two main concerns about this particular stream restoration. My first major concern has to do with the anchoring of the banks using large boulders. This process can cause a disconnect between the stream system and its floodplain, which is the land adjacent to the stream that can experience flooding during a storm event. This disconnect occurs due to the direct application of the boulders and because of stream incision, or deepening, which is a byproduct of the inability to migrate left and right. The connection between a stream channel and its floodplain is important because it allows the surface water in the stream to interact with the groundwater in the floodplain. This can facilitate filtration or sediment and toxic substances from the stream improving the overall water quality.

The other concern I have with this project is that while the goal may be to reduce long term bank erosion in the short run large amounts of sediment are being disturbed and transported downstream (Figure 2). This sediment will not only affect Paint Branch Creek but also the North East Branch of the Anacostia, the mainstem of the Anacostia, and possibly even the Chesapeake Bay. At this time of year excess sediment can be especially problematic due to the fact that the ground is already so wet there is no room to store water, which normally would allow suspended sediment to settle out. It is by no means my job to judge the restoration effort taking place on Paint Branch Creek and in reality it is too soon to make a final judgement anyways. However, I wanted to point out the concerns I had about the project and why it is important to make sure a restoration is actually meeting its goals. Is this stream restoration helping the stream or harming it, I will leave that for you to decide.

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Craig, L.S., M.A. Palmer, D.C. Richardson, S. Filoso, E.S. Bernhardt, B.P. Bledsoe, M.W. Doyle, P.M. Groffman, B.A. Hassett, S.S. Kaushal, P.M. Mayer, S.M. Smith, P.R. Wilcock. 2008. Stream Restoration Strategies for Reducing River Nitrogen Loads. Frontiers in Ecology and the Environment, v. 6.