Good Roads, Clear Creeks
Reducing erosion to improve aquatic habitat:
The single largest cause of salmon population decline in the Mattole is excessive erosion into streams, largely from roads and streambank failures. Sediment suffocates salmon eggs by clogging spawning gravel, and fills in cool, deep pools which serve as critical rearing habitat.
Starting at the headwaters and working downstream, sediment sources like culverts, poorly draining or abandoned roads, stream bank failures and landslides are prioritized and treated. Access roads are storm-proofed, abandoned roads are recontoured, and stream crossings are upgraded to meet fish passage and sediment delivery guidelines.
Staff visit with landowners to identify erosion sites with the potential to deliver sediment into watercourses. Findings from these visits and follow-up field surveys are then presented to landowners in the form of a customized report. With permission from landowners, the Council then carries out the prescribed restoration work.
Petrolia Project Area
An eroding streambank along the mainstem Mattole river prior to project implementation
In 2007, GRCC personnel performed a sediment source assessment on the roads and erosive streambanks within the lower Mattole area. The scope of this project encompasses the area from McGuiness Creek to the Mattole River estuary. GRCC staff identified over 100 sites with the potential to reduce 72,540 cubic yards of sediment from entering the watercourses. The implementation phase began in the summers of 2008 and will reach completion in 2011.
To measure the effectiveness of the upcoming sediment reduction work in the Lower Mattole, turbidity samples were taken at selected creeks. Turbidity, a measure of the water's cloudiness, is an indicator of the amount of sediment a stream is carrying and therefore it's suitability for fish habitat. Samples were collected during the winter of 2008 and the project will continue for up to four years. The results will give us a better understanding of how to make our work more effective.
| Attachment | Size |
|---|---|
| Petrolia Area Sediment Assessment Report | 982.18 KB |
Bear Creek Project Area
The GRCC program is working to reduce sedimentation in the Bear, French and Wolf Creek sub-sheds to the Mattole River. The project is scheduled to reach completion in October 2009 with a total sediment savings of approximately 50,000 cubic yards. Nearly fifty culverts were replaced, numerous drivable rock-armored fords were installed on seasonal roads, and miles of road were reshaped to reduce surface erosion. In addition, two arch culverts were installed with the largest site located along Chemise Mountain Road in the headwaters of South Fork Bear Creek. Large streambank stabilization and fish habitat enhancement projects were also performed in the project area, including a large site visible just upriver from the Ettersburg bridge.
An inappropriately placed and undersized culvert (left) that acted as a partial barrier to salmonids was replaced with a larger and appropriately angled culvert (right).
An eroding streambank contributed large amounts of sediment to all areas downstream (left). After project completion, the toe of the slide was stabilized with boulders and large wood was placed for enhanced salmonid habitat.
| Attachment | Size |
|---|---|
| Bear Creek Sediment Assessment Report | 380.92 KB |
Blue Slide, Mattole Canyon & Grindstone Creek
As the largest sediment savings project to date, GRCC will stabilize over 300,000 cubic yards of sediment by the end of this project in October 2010. This geographic area of the Mattole watershed has unstable geology and is prone to large landslides. Numerous instream large-rock and willow-bioengineered structures have been installed at the toe of major slides along these creeks. These structures are designed to stabilize the stream bank by directing the force of the water away from unstable areas. This work facilitates accelerated growth of streamside vegetation, further stabilizing the riparian corridor and shading the creek. Numerous roads have also been storm-proofed within this large project area.
An undersized culvert on Blue Slide Creek (left) is replaced with a bridge to allow for unimpeded high water flows in the winter. This culvert acted as a velocity barrier during high flows as the creek was forced, at high speed, through the undersized culvert.
In the summer of 2009, GRCC replaced this failing bridge abutment (left) that was leaking toxic creosote into Mattole Canyon Creek with a solid cement foundation that will withstand 100-year floods (right).
| Attachment | Size |
|---|---|
| Blueslide to Grindstone Sediment Assessment Report | 493.95 KB |
Eubanks Project Area
During the summers of 2006, 2007 and 2008 the GRCC program performed erosion control projects within Big Finley, Little Finley, Buck, Deerlick, Eubanks, and Nooning Creeks; all tributaries to the Mattole River. Approximately 70,760 cubic yards of sediment have been prevented from entering the Mattole River watershed. Several miles of road have been reshaped through crowning and outsloping. Over fifty culverts have been installed, all designed to withstand a 100-year flood events. Some of the most significant work included replacing old culverts that were impeding fish access and installing bottomless pipe arches. These structures allow salmon and steelhead trout to freely migrate under the road expanding their spawning and rearing habitat.| Attachment | Size |
|---|---|
| Eubanks Sediment Assessment Report | 304.04 KB |
Ranchlands Water Quality Program
The MRC seeks to foster good working relationships with all land owners throughout the watershed and has developed this program as a means of outreach and relationship building with the ranchland ownership sector of the community.To date, sediment assessments have been performed on six ranches (not including three large
ranches within the Bear Creek and Blue Slide to Grindstone project areas that have participated in the GRCC program). GRCC staff is actively pursuing further ranchland involvement and development of implementation projects on these properties.