Projects are the means by which nutrient levels entering the waters of Coeur d’Alene Lake and its tributaries can be managed.
Projects can include improvements to shoreline vegetation, river and streambank erosion control, wastewater system improvements, stormwater control and treatment, or other Best Management Practices for a variety of land uses. If you have an idea for a project or have any questions, Contact Us!
Avista/Riverbank Erosion Stabilization
Our team has been working with Avista Utilities to stabilize riverbanks throughout the basin. Avista also works with our team to help prevent and manage Eurasian watermilfoil infestations.
Riverbank Erosion Projects:
Our most recent bank stabilization endeavor is a project near the Shadowy St. Joe Campground on the St. Joe River. The project encompasses roughly 7,000 linear feet of riverbank. These high eroding banks are the result of boat wake-induced erosion that occurs at the summer water level elevation, which is controlled by the Post Falls Dam on the Spokane River. The boat wakes cause a “notch” to be eroded away at the base of the vertical banks. At this St. Joe project location, the vertical banks above this notch are up to 10 feet in height! As the notch digs into the bank, the weight of the soil above it causes the upper bank to slump down, as is shown in the picture below.
The loosened soil then washes into the river and makes its way downstream to Coeur d’Alene Lake. Soil takes with it, among other things, nutrients that are attached to the particles. Phosphorus is the primary nutrient of concern associated with soil, as it likes to attach to soil much more than nitrogen. Phosphorus is a nutrient used by plants for growth. In excess, it causes excess algae and plant growth in Coeur d’Alene Lake. Excess plant growth and subsequent decomposition can deplete deeper water layers of oxygen in summer months. This phenomenon is what we are trying to prevent. See our History page for more information.
The Shadowy St. Joe project utilized existing vegetation, rock, and newly-placed willow hardwood cuttings to stabilize eroding riverbanks. The willow cuttings are simply long branches of willow, collected while dormant, that are trimmed of any branches. The cuttings were then tied into bundles of 5 stems. The willow bundles were placed along the base of the eroding bank. Some of these willow bundles can be seen in the picture above, prior to rock placement. Rock was then used to fill in the eroded notch in the lower bank, anchoring the willow bundles in place (see picture below).
The willow bundles were trimmed down to about a foot of exposed height once the rock placement was complete. This allows them to focus their energy on root growth first. The willow bundles will begin to grow roots as they warm up in the spring, followed by branches, leaves, and all of the benefits that come with healthy vegetation. Further slumping may occur in the future, but, ideally, this slumping will land on top of the rock, stabilize the upper slope, and allow other vegetation to re-establish. This, combined with the willow bundles, will stabilize the upper bank as well as provide a good vegetated riparian zone, which will provide filtration of runoff and wildlife habitat. In some areas of really high banks, some of the upper bank may need to be pulled back to prevent it from washing into the river. Each year, the project will fill in, and eventually, the rock will hardly be visible under the lush new vegetation.
The Lake Management Team is working with the City of Coeur d’Alene, University of Idaho, CDA Vision 2030, and others to identify potential innovative demonstration projects for stormwater treatment. Currently, grassed infiltration areas (GIAs) are used throughout the City of Coeur d’Alene to treat stormwater runoff before it goes into groundwater of surface water, such as Fernan Creek, Coeur d’Alene Lake, or the Spokane River. A GIA is a depression designed to collect runoff from impervious areas. There is usually an injection well or other structure included to drain overflow. GIAs can be effective ay pollutant removal. However, these are often seeded with Kentucky bluegrass, which requires maintenance such as fertilizing, pest control, and irrigation. Addition of these items increases the potential for nutrients and other items to enter our waters in addition to taking time to maintain.
Other practices exist that offer some flexibility in design. They have proven useful in other areas but need to be evaluated for their effectiveness in our climate, with our soils, and under a variety of site constraints. There are many potential sites we are investigating for alternate stormwater management techniques. We are hoping to identify practices that would require less maintenance, improve water quality going into ground and surface water, and serve as a demonstration site for others to study and learn from for other projects.
The Lake Management Team is always on the lookout for potential shoreline improvement projects. This includes streambanks, riverbanks, and lake shoreline areas. These areas are significant in preserving water quality and habitat. Shoreline landowners have a special relationship with adjacent waterbodies, and likewise, have a special opportunity to contribute to the collective effort of preserving Our Gem. We are especially interested in projects that would establish shoreline vegetation comprised of trees, shrubs, grasses, and forbes, while maintaining a view corridor and access to the shoreline itself. These values are not mutually exclusive, and we would like to be able to work with a landowner to demonstrate that to others. If you have shoreline property and would like more information, Contact Us. You can also find more information on ways to minimize any negative impacts from your property (whether you are on the shoreline or not), by checking out our Lake*A*Syst materials.