Building P.A.L.S. With Our Pals

by | Aug 4, 2021 | news | 0 comments

Building P.A.L.S. With Our Pals

TUC, Cows & Fish, and Clearwater County staff stack woody debris in Radiant Creek for a PALS. Willow and poplar stakes in the foreground. 

Building P.A.L.S. with our Pals-Radiant Creek is a tributary of central Alberta’s Clearwater River, which is considered critical habitat for at-risk Bull Trout. In the recent past, Radiant Creek has flooded out of its natural channel downstream of the Forestry Trunk Road. It is likely the road and culvert or bridge at the time exacerbated the effects of flooding resulting in a flow constriction, causing increased stream velocity – similar to the effect you get when you pinch a garden hose. Due to grazing and trampling of the riparian area and stream bed by cattle and feral horses, this degraded reach of the creek has not been able to recover and is shallower and wider than upstream and downstream reaches.

The new (post-flood) channel of Radiant Creek below the Forestry Trunk Road has very little high-quality habitat available for Bull Trout and other fish species and usually becomes very low and warm in late summer. TUC began a rehabilitation project on this reach in 2020 and, working with the local grazing allotment holder, installed enough fencing to exclude the cattle and horses from a 200-meter section of the stream and riparian area. In addition, 20 acres of shrubs were removed from the valley to increase grass cover and offset grazing opportunities lost by shrub encroachment in this portion of the Clearwater valley. Much of the intense use of the riparian area is due to this shrub which limits the grazing areas available to cattle and horses. Shrub encroachment is likely due to the lack of low-intensity fires which would have historically burned these grasslands prior to European settlement.

Building P.A.L.S. With Our Pals

TUC staff installing a bank-attached PALS on Radiant Creek.

Since fall 2020, TUC staff and volunteers have planted well over 1000 live willow and poplar stakes within the fenced area to improve riparian health. The stream itself remains wide and shallow with little habitat and structure. To address this, TUC has implemented a “low tech processed-based restoration (LTPBR)” pilot project. LTPBR is a stream restoration concept that uses simple, low-cost structural additions in structurally starved riverscapes. The specific technique used at Radiant Creek is known as Post-Assisted Log Structures (PALS). PALS are simulated log jams made by piling logs and branches in the river and pinning them in place with untreated wooden posts. The PALS are strategically placed in order to encourage the stream to meander, create undercut banks, scour deeper sections, and gather fine materials into gravel and sand bars – essentially to mimic and promote the natural process of wood accumulation. The goal is to create complex habitat and stream function using all-natural materials and the power of the flowing water. This process takes time, and the PALS are built to interact with high water events and spring freshets as well as the normal seasonal flows of the stream. Eventually, the untreated posts will rot, and the PALS will transition from man-made structures to lose woody debris in the stream.

In 2025 the fencing will be removed after the site becomes more resilient to cattle and horse traffic. During this time, TUC and our partners will continue to monitor the success of the project and make adjustments as needed to ensure positive outcomes, including improved riparian health and function, improved water storage and retention, and year-round habitat for Bull Trout.

Building P.A.L.S. With Our Pals

Completed PALS along a channelized reach of Radiant Creek.

Big thanks to Cows and Fish and Clearwater County Landcare staff as well as the volunteers that helped install PALS and plant willow stakes, to Sundre Forest Products for providing woody debris to use in the structures, and the Alberta Backcountry Hunters and Anglers for donating to the project. Last but not least, thank you to the allotment holder who has supported these recovery efforts since the project began. This project is financially supported by Alberta Environment and Parks through the provincial Native Trout Collaborative, funded by the Canada Nature Fund for Aquatic Species at Risk and the Alberta Conservation Association.

Trout Unlimited Canada is a nonprofit, charitable organization. Donations are tax deductible as allowed by law.