BHRA is excited to announce that excavation work on Rattlesnake and Juniper Side Channels has been completed, effectively reconnecting .45 miles of complex habitat back to the Bighorn River! Since construction of the Yellowtail /Afterbay dams, Bighorn side channels have become increasingly disconnected from the main river due to instream channelization that has, over time, led to sediment build up at side channel entrances. This build up of sediment, along with vegetation encroachment, has cut off flow into many channels, preventing wild trout from accessing vital spawning and rearing habitat -especially during drought years.
This build up of sediment, along with vegetation encroachment, has cut off flow into many channels, preventing wild trout from accessing vital spawning and rearing habitat -especially during drought years.
In 2020 BHRA worked with contractor Karin Boyd (Applied Geomorphology, Inc) to identify side channel connection potential on the Bighorn. From this work, a total of 13 side channels were identified as "top tier" candidates for reconnection. Rattlesnake and Juniper were chosen to reconnect in 2021 based on their location, access, and cost/benefit ratio.
Last week, BHRA contractor Mike Sanctuary (Confluence Consulting) led survey and excavation teams to remove a total of 540 cubic yards of compacted material from the entrances of Rattlesnake and Juniper, and within their length, returning the channels to their historic slopes and connecting them to the river. Excavated material was then used to angle the openings of the channels so that they veered from the main channel at an angle of about 40-45 degrees, which has been shown by studies to be effective at maintaining sediment transport and keeping the heads of the side channels open.
We are proud to announce that both channels are now actively passing water, increasing the amount of habitat available to Bighorn wild trout during low water years. Over the next several months, BHRA will be monitoring the success of these projects and sharing more. In the meantime, we encourage you to take a few moments to view the before and after photos provided below. For more information on excavation work, please visit the Side Channel Reactivation Design report.
Rattlesnake Side Channel- Before and After Photos
Rattlesnake entrance before (left) and after (right) excavation:
Approximately 120 cubic yards of material was removed from the head of Rattlesnake Channel, and within the channel itself, to return the channel to its historic slope.
Rattlesnake Channel Before (left) and After (right):
Prior to excavation, Rattlesnake Side Channel only contained trout suitable flows when releases were over 2500cfs. After excavation, flows are connected are 1750cfs.
Rattlesnake Lower Channel before excavation (left) and after excavation (right):
Excavated material was redistributed along banks to narrow the channel at designed locations to help maintain velocities that encourage downstream sediment transport (helping keep the channels open over time).
Juniper Side Channel- Before and After Photos
Juniper Side Channel Entrance before excavation (left) and after (right):
Approximately 420 cubic yards of accumulated material was moved from the entrance of Juniper side channel and within the channel itself, to return the channel to its historic elevation (slope).
Juniper Channel before excavation (left) vs. after excavation (right):
The historic bed of the channel was manually reinforced throughout the .27 mile length channel, with excavated materials used to narrow points of the channel that widened over time.
BHRA Board member and Research Chair Jim Chalmers installing project signs.