Why Focus on Stream Restoration Projects?
Stream segments in the Lower Des Plaines River and Lower DuPage River watersheds are failing to meet the Clean Water Act’s (CWA) standards for water quality and aquatic life. The watersheds are affected by several stressors, including:
- Municipal and industrial discharges of wastewater, also called point source pollution
- Polluted stormwater runoff, also called nonpoint source pollution
- Modifications that throw off the stream ecosystem, such as:
- Increased amount of stormwater directed to streams resulting in more flooding and flashiness – water levels quickly rising during/after rain and quickly going back to normal
- Dams that interrupt stream flow
- Changing a stream’s natural form, such as straightening or deepening it
- Loss of in-stream habitat
- Absence of native vegetation along stream banks, making streams more prone to streambank erosion and contamination from stormwater runoff
To restore stream sections that fail to meet CWA standards, attention has been focused on limiting point source pollution from wastewater treatment plants. This focus has resulted in significant improvements in stream health in the 80s and 90s. Yet, in 2016, the US Environmental Protection Agency reported that over half of surveyed US river and stream miles were still failing to meet CWA goals. So, while managing pollution levels at wastewater treatment plants continues to be important, it is not the only answer to all of the problems that streams face.
We now are expanding our focus to include projects that have a more holistic approach to stream health. Stream restoration projects reverse modifications to stream structure and function, resulting in a healthier ecosystem and better water quality. Stream restoration projects have more potential to improve overall waterway health and amplify the improvements made by wastewater plant upgrades.
Before starting a stream restoration project, we look at monitoring data which help us identify the biggest stressor affecting streams and select projects with the greatest potential to improve water quality.
Stream Restoration Techniques
The majority of dams in our region are obsolete. Not only do most dams no longer serve their original purpose, they are also a major obstacle to restoring healthy streams. A dam cuts off a river’s flow. This has several consequences:
- Public safety: Low-head or run-of-river dams are shorter dams that allow water to flow over them. The water that flows over the top of the dam creates a current that is able to pull people down and trap them underwater. While they do not look dangerous, many people have drowned at low-head dams.
- Water quality: Rivers and streams are meant to flow and freely move sediment downstream. By cutting off a waterway’s natural flow, water slows and pools behind the dam, causing sediment to accumulate. The water upstream becomes shallow and nutrient-rich. This creates conditions that deplete oxygen in the water and make it difficult for aquatic life to thrive.
- Aquatic life: Dams prevent fish passage. In several streams in our watershed, certain fish species are only found downstream of the dam. Dams also impact the health and diversity of aquatic life by degrading water quality and habitat.
- Maintenance costs: Dams require upkeep. Maintaining low-head dams, removing sediment that accumulates upstream, and repairing downstream bank erosion can be costly.
- Recreation: Dams prevent boaters from passing dams safely. Boaters must exit the stream and carry their boats over land to pass dams. Recreational fishing is also negatively impacted by low-head dams since dams degrade water quality, habitat, and fish populations,
Removing dams improves water quality, habitat, fish diversity, safety and recreation.
A root wad is a trunk of a dead tree with the roots still attached. In stream restoration projects, root wads are embedded into the streambank to stabilize the streambank and provide cover for young fish to hide from predators.
Many rivers and streams were straightened to increase the speed of water flow and gain more farmable land along a waterway. Problems from straightening, or channelization, include streambank erosion and loss of in-stream habitat.
By re-meandering a stream, or adding curves, we increase the stream’s length and slow the water flow. This lessens the force on the streambank, reducing soil erosion. Adding bends to a waterway also adds a greater variety of habitat for aquatic life.
Deep-rooted native plants stabilize the streambank and provide habitat along a waterway. Native vegetation also reduces the amount of polluted stormwater runoff flowing into streams by acting as a buffer between the landscape and waterway. This vegetation also provides habitat for the adult stages of aquatic insects that live in the streams.
Cobbles and Boulders
Diverse stream substrate, or material at the bottom of the stream, provides more in-stream habitat for aquatic life. Adding large pieces of substrate, like cobbles and boulders, creates riffles. Riffles are areas of shallow, fast-flowing water that help add oxygen to the water and provide habitat for certain species of fish and macroinvertebrates.
Floodplain restoration is sometimes done in conjunction with stream restoration. Reconnecting a waterway to a floodplain allows for stormwater management that benefits the stream, surrounding habitat, and residents living in flood zones.