Fort Collins Nursery is undertaking a riverbank stabilization project in order to protect our property from severe damage by high river flows and minimize our impact on the riparian habitat that exists along the Cache la Poudre River. The Nursery’s entire south perimeter borders the Cache la Poudre River.
What’s the problem?
During years with exceptionally high water flow in the Cache la Poudre, it is not uncommon for large pieces of the riverbank to collapse as the water undercuts the shoreline.
In 2011, the Cache la Poudre River watershed has recorded incredible snow pack, measuring 176% of the annual average. In fact, according to the USDA,
At Cameron Pass, a new record snow pack was measured at 48 inches of water equivalent. This record exceeds any measurement since that site was established in 1936, making it one of the oldest snow courses in the state.
USDA Natural Resources Conservation Service: Colorado Basin Outlook Report, May 1, 2011 (http://www.co.nrcs.usda.gov/snow/fcst/state/current/monthly/data/reportselection.html)
This means that if all the snow in the Cameron Pass area were melted, it would be the equivalent of 48 inches of standing water. As that snow melts, all of it is channeled through the Nursery’s back yard, posing severe erosion risks as it makes its way downstream.
What steps are we taking?
In cooperation with the Army Corps of Engineers, Fort Collins Nursery has developed a plan to mitigate damage to the riverbank by using stone and native plants as reinforcements.
We will place large boulders along the riverbank in order to stabilize the soil. The placement of these boulders, or “riprap,” is a common practice along shorelines and waterways where erosion is a concern. By using native stone instead of concrete, asphalt, or other synthetic materials, we eliminate the chance of chemical breakdown or runoff that could poison the aquatic habitat downstream.
In addition to placing riprap along the banks, we are building a “stream barb” at a particularly prone spot along the Nursery’s south bank. Stream barbs are rock structures that extend into the stream flow to modify flow patterns and riverbed topography. Stream barbs redirect the primary force of the flow of a stream or river away from eroding banks toward the center of the streambed. They also serve another purpose: they create an underwater habitat for aquatic life, forming deep pools with large openings that can shelter fish, crayfish, turtles, and other aquatic species.
This summer, after the peak flow has subsided, we will be planting a variety of shrubs and trees along the riverbanks that will help stabilize the soil and help trap sediment as it is carried downstream. The area where the roots meet the water becomes a rich habitat for aquatic and riparian life. The primary plant used in riverbank stabilization is Coyote Willow (Salix exigua), as wells as several varieties of Cottonwood (Populus sp.) and Western River Birch (Betula occidentalis).
Planting vigorous native plants along our riverbank serves a secondary role that is not related to riverbank stabilization. By establishing a strong plant habitat along the riverbank, the runoff from our irrigation is filtered through a dense network of plant roots before it reaches the river. We are continuing to be a responsible neighbor and caretaker of our community’s precious riparian environment.
What can you expect to see in years to come?
Initially, the area we are working on will look a bit rough. The stone will appear very out of place. It is native stone but it is not the same color as most river cobbles. The plants we are placing will be very small. As the riprap, stream barbs, shrubs and trees mature, you will see several things happening.
- First, the riprap will be less obtrusive as weather, water, and sediment stain and color the rock. While the riprap will never look like natural river rock, Mother Nature will do her part to help it blend as much as possible.
- Second, the willow, cottonwood, and birch will grow quickly to soften the landscape. These fast-growing varieties are all native Colorado species and will quickly blend into the surrounding environment.
- Third, the stream barbs, which will alter the flow in the river channel, will create sandbars and sediment deposits that will allow the establishment of other native species. We may see rushes and cattails, boxelders, willows, and maybe a few fun surprises, too!
Our goal with this project is to protect our natural environment while ensuring the stability of the riverbank that allows us to operate our nursery. We feel lucky to have such a wonderful and scenic river flowing through our nursery, and with this project, we hope to keep the river healthy, beautiful and safe.
For more information, call 970-482-1984, or e-mail [email protected].
Read more about the flooding concerns in the Fort Collins Coloradoan.
Originally published on May 19th, 2011. Updated on June 20th, 2011.