Mattole River Estuary Project Update
Thanks to The Nature Conservancy for this great piece on the Mattole Estuary Project!
Restoring the Mattole River Estuary – Defense for the Drought?
Large wood structures have been added to enhance salmon habitat in the Mattole River estuary. In the foreground, construction equipment helps build the deep trenched willow baffles on the upstream side of the newly restored slough channel. © Abi Queen
Slough excavation site during project work. © Nathan Queener
Close-up of a large wood structure and the slough excavation. © Abi Queen
Yellow marks show where whole trees are added at the mouth of the slough. Upstream of the main slough excavation site, blue lines represent the first 50 feet of the trenches where whole trees with root wads were placed. Black lines represent the remainder of the trenches, where logs and willow cuttings were placed. © Mattole Salmon Group
Last winter’s drought impacted many things, including the coho, Chinook salmon, and steelhead that live in the Mattole River. A significant portion of the returning adult coho and Chinook this past fall and winter were limited to the lower Mattole River downstream of Honeydew due to low flows. The result? Fish spawned where they could in the lower river, rather than heading further upstream where the normally go and where stream habitat is better for growing fish. So what can we do about this situation? What will the young fish do?
What can we do?
We accelerate our efforts to restore the habitat they can reach – by returning the Mattole estuary back to a healthy estuary/lagoon with deep pools and extensive riparian and slough habitat.
The “Cohotel” – Side-Channel Refuge for Coho
There is a complex of elevated slough channels along the south bank of the Mattole River estuary that were disconnected from the river after the 1992 Triple Junction earthquakes uplifted the area by 3-5 feet, and subsequent deposition from over-bank flows filled in the old river channels. This slough restoration project excavated 250 feet of one of these historic channels to create off-channel habitat for juvenile salmonids in the summer of 2014. This slack-water habitat will have cooler water temperatures than the main river and an abundance of insects (food for juvenile salmonids) from the extensive over-hanging riparian vegetation. It will serve as a refuge from high water velocities in the winter and be a veritable paradise of cool water temperatures and abundant food in the summer. The work dredging the old, filled-in and uplifted slough channel was finished in early July. We have also completed extensive terrace margin treatments with willows, whole trees, wooden posts and logs, and thousands of willow cuttings. The willow and wood trenches are designed to lengthen the life of the slough excavation area by providing hardness (vegetation and logs) upstream. When the terrace gets inundated with water, the willow will also help to settle fine sediment upstream of the slough channel.
Helicoptering in “Log Cabins” for Fish
Two hundred Douglas fir trees were helicoptered into the estuary to accelerate the rebuilding of fish habitat. In summer, fish can rest in these deeper, cooler pools created by these log structures (see close-up on left) when flows are low, and in winter, shelter from the high flows. Flying in the logs took only 11 hours! This restoration project was fast and actually cheaper than trucking them in.
In 2012, the Bureau of Land Management (BLM), working with local landowners, watershed groups, and numerous other state and federal agencies, developed a 5-Year Restoration Plan for the estuary/lower river on BLM lands.
The slough project partners are the Mattole Salmon Group and the Mattole Restoration Council who are completing all of the associated willow planting work, and Patrick Queen, a local heavy equipment operator and problem solver. Funding comes from the California Department of Fish and Wildlife, The Nature Conservancy, the National Fish and Wildlife Foundation, and the National Oceanic Atmospheric Administration, with funding and staff support from the Bureau of Land Management, and tree donations from Ellen Taylor and Michael Evenson.
The helicopter wood project was led by the Mattole Salmon Group, with funding and technical support from the National Oceanic Atmospheric Administration, The Nature Conservancy, and the California Department of Fish and Wildlife.
Read more about the slough project and helicopter wood project.