The bridge abutments on the Pierce Creek bridge have been replaced. The project is a cooperative venture of the Mountain Home Highway District and the Boise National Forest. The abutments are treated laminated wood beams and posts, and driven several feet into the ground next to the stream.
The bridge over Pierce Creek, a spawning tributary to the South Fork of the Boise River
The project was completed in fall 2018 and secures the bridge for the long term.
A mud crust over the plate on the bridge. Mud deposited from the numerous debris flow episodes 2013-2014.
The bridge was placed on its original sill in November 2011. The Elk Complex Wildfire of 2013 led to massive debris flows in Pierce Creek and ultimately would have compromised the foundation for the bridge. So the decision was made to life the bridge and replace the substructure and put it back in place, which happened in fall 2018.
Future high flows and flooding will easily pass under the bridge. Pierce Creek fish passage to its headwaters will continue.
Check out this video of rainbow trout spawning in Cow Creek.
Along with the video came this field dispatch:
You can see some smaller fish darting in and out around the female on the nest at 3:48, and again around the last 2 mins. I couldn’t figure out what exactly the smaller fish were doing if they were trying to get in and feed on the eggs, or fertilize the redd or what….
Highlights: redd making at 5:28, 6:32, and 7:43.
I have a few other videos of the other pairs I saw. 4 pairs total with some other males hanging around all in about 100m at the bottom of the grade. I see them in here every year but never this many and never this big.
Make plans for Saturday November 9th for volunteer planting along the South Fork Boise River to kick start the recovery of the river corridor from the recent wildfire and mud flow events.
The plan is to meet at the parking lot near Albertsons near Federal Way and Gowen Road (next to Exit 57 on I-84) at 8:30 a.m. We will organize those who want to car pool and to leave promptly at 9:00 a.m. for the drive to the South Fork of the Boise.
Thanks to the more than four dozen people who signed up to volunteer at the September 11 meeting we think we will have a core group to start. But additional help is needed for this effort. We are working to get the word out with the fly shops and the fishing clubs. The Boise National Forest is determining what plants and trees will be planted, they types and quantities. Needed tools are being identified. At this time we need you to sign up to help. You can call Bob Caldwell at (208) 322-5539 and leave a message or email [email protected].
There are several areas where the debris flows scoured the gound the removed vegetation. These areas will be one to plant. Other sites where the fire burned may also need planting, but in many cases we are already seeing willow begin to regenerate on its own from the roots that were not killed in the fire.
Knowing in advance how many people are coming will help planners determine how much we can get done. Lunch will be provided on site. And, there is not Boise State football game on November 9th so don’t worry about that potential conflict.
Longer-term visitors to this website may recall seeing stories when the Pierce Creek Reconnection Project started and completed and the role tributaries play in maintaining a fishery.
The mud and debris flows from Pierce Creek on September 12th were both substantial in amount delivered to the South Fork of the Boise River and unique in that the entire flows went under the bridge.
This was by design because when the project went forward in 2011 project engineers used data on the high flow estimates for Pierce Creek. And while not to spike the ball in the end zone or anything, it is satisfying to see something perform pretty much as planned.
But the story is not over. There could be more weather events that cause more flooding with a similar mud slurry. And there are lasting effects from the September 12 event that will need repair to the stream channel.
While the slurry was confined to under the bridge many of the grade control structures in the channel were swept into the river. Here is how the channel looks today:
Looking downstream from Pierce Creek bridge September 16, 2013
Many boulders are covered in mud but many are also now in the South Fork of the Boise River. A large drop in the stream bed as seen in the foreground (bottom of the photo) did hold in place as that large boulder is part of the channel that was in place prior to the removal of the culvert in 2011. The vertical drop creates a barrier to fish wanting to move upstream.
Compare the above photo with that from early 2012 just prior to planting the site:
Early spring 2012 showing the step pools in Pierce Creek
The right bank of Pierce Creek through the trees was scoured of nearly all the brushy vegetation, brush that is clearly visible in the 2012 photo. Meanwhile the plantings on the left bank are still in place after the mud flows.
So work will be done to shore up the grade control of the stream and make it possible for fish to be able to move freely upstream and downstream in Pierce Creek. Thanks to a generous donation of time from Quadrant Consulting the field survey work will commence later this week. We salute Quadrant’s contribution to the South Fork fishery! As survey work transitions to construction we will provide updates.
