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.

The same eroding streambank site as the above photo after project completion in summer 2009.  The slide was stabilized by reducing the slope, anchoring the toe with rip rap, installing a "bioengineered rip rap wing deflector" (large wood and boulders anchored into place to deflect the current and prevent further erosion), and the planting of willow, alder, and other native riparian species.
Petrolia Area Sediment Assessment Report982.18 KB