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Forest Thinning and Gully Repair

Blogpost published on: Friday, October 22nd, 2021

‘Slash Ain’t Trash, It’s Beneficial Biomass!’  – Brock Dolman

For the past few months, OAEC’s Wildlands team has been working hard applying for permits to restore a number of eroding ephemeral (Class III) watercourses that run through the OAEC & Sowing Circle property. During the rainy season, these channels deliver sediment downstream to Dutch Bill Creek, one of the most critical watersheds in the Russian River basin for the recovery of endangered Coho salmon and threatened Steelhead Trout. Gullies also effectively dehydrate the adjacent landscape by draining shallow groundwater to their low points, just like pulling the drain out of a bathtub.

One way of stabilizing and repairing gullies is to pack them with brush in order to slow the flow and distribute the energy of water, trap soil and leaf litter particles, and ultimately arrest sediment delivery downstream. With various limbing and thinning projects underway, we recognized the opportunity to stack functions and use the abundance of resulting material onsite (often called “slash”) to stuff nearby gullies! To do this legally, we had to get two permits: a General 401 Water Quality Certification for Small Habitat Restoration Projects through the State Water Board and a Lake and Streambed Alteration Agreement through CDFW.

With a brief window of dry weather stipulated by our permits, a group of OAEC staff and volunteers got to work on Monday and stuffed nearly 200 feet of gully. We started by carefully placing fresh green boughs (often fir or redwood) with the tips facing upstream in an interlocking fashion as if we were plastering the channel bed & banks, then amended with woody debris until filling the entire height and width of the gully. The end result? A dense but porous matrix that will stop erosion, and as it decomposes over time, will sequester carbon, create a rich compost sponge for nearby trees and vegetation, and increase our upland water holding capacity!

Check out this brief 1-minute of Brock explaining the process.