Sediment & Wood Augmentation – Steel Bridge Habitat Enhancement

Aerial imagery of the Steel Bridge Boat Launch and upper Steel Bridge reach of the Trinity River. [Elliot Sarnacki, Trinity River Restoration Program]

A recent synthesis of research documents (linked here) identified and recommended four additional areas within the Trinity River in need of habitat enhancement below Lewiston Dam.

Dams disrupt the natural movement of water, rocks, and wood downstream resulting in a lack of loose, well-sorted sediment and the structural complexity that salmon and steelhead need to successfully spawn, protect their eggs, and rear once hatched. To make up for the loss of these materials below a dam, river restorationists augment materials in areas identified as depleted.

Through placement and monitoring fluvial geomorphologists have learned that augmented materials do not mobilize as extensively as previously assumed on the Trinity River due to the disruption of natural flows. Trinity River sediment transport requires numerous strategic augmentation locations in order to work prescriptively to address deficiencies. The Steel Bridge location was selected for augmentation this season (2026) because it offers the right conditions for restoring salmon habitat; including equipment access, proximity to existing riffles, and a riverbed that has become armored and lacks spawning gravel.  

Examples of sediment & wood augmentation

Wood racked at the Upper Conner Creek Restoration Site post winter flows. [USFWS]
Gravel and wood recruitment at Oregon Gulch post WY26 winter flows. [Aaron Martin, Yurok Tribal Fisheries Department]
Wood racked at Upper Conner Creek Restoration Site post winter flows. [USFWS]
Sediment placed for recruitment at the Cableway site, 2023. [TRRP]
Sediment placed for recruitment at the Cableway site, 2023. [TRRP]
Hatchery reach depleted of appropriate sized sediment in 2020. [TRRP]
Hatchery reach post-sediment augmentation 2021. [TRRP]

When combined with adding appropriate sized sediments large wood additions can interact with the river across 3 scales.

  1. Geomorphic change scouring pools and sorting gravels and fines. 
  2. To provide habitat (for juveniles and adults);
  3. Hydraulic forcing at elevated flows;

In the image to the right, constructed wood jams are forcing flows in two directions encouraging geomorphic change (center right of image), whole trees placed for habitat during construction (lower right), and whole trees being recruited from natural process and bank erosion (upper center). 

Photo: Drone imagery showing sediment and wood interacting with flow at Oregon Gulch. [Aaron Martin, Yurok Tribal Fisheries Department]

By adding appropriate sizes of sediment and placing locally harvested trees into the river, we can help the river rebuild vital habitat for spawning, support food webs, enhance river health and natural processes. These materials are typically placed prior to higher flow periods, allowing the river to naturally distribute them to form complexity and create dynamic habitat for Trinity River salmonids.

Project Specifics

When will 2026 Sediment and Wood Habitat Augmentation take place?

Starting the week of March 16 residents will likely see an increase in traffic, including large trucks on Steel Bridge Road for hazard tree removal and material & equipment staging. Sediment and wood in-channel work is likely to begin after April 1 and will be completed prior to spring restoration releases from Lewiston dam scheduled for mid-April.

What to Expect

  • Timing: Work is scheduled during low-use periods in late March and will be placed prior to flow releases in early April to allow the river to distribute the sediment and wood naturally.
  • Sediment Size: Spawning-sized sediments (roughly 3/8 inch to 5 inches) will be trucked, stored and then placed in the river channel.
  • Wood: Locally harvested hazard trees identified for removal will be removed, stored and placed in the river channel to build low-flow habitat.
  • River Access: Crews will use the Bureau of Land Management river access point downriver of the Steel Bridge boat launch.
  • Materials Source: Standing dead trees will be harvested from the Steel Bridge Campground, Boat Launch and Steel Bridge Road. Spawning sized sediments are stored at Lowden Ranch.
  • Safety and Monitoring:
    • The project area directly adjacent to the project boundaries along the Trinity River will be marked with signs and/or buoys in accordance with the requirements specified in Title 14, Article 6 of the California Code of Regulations. Fencing or other barriers will be installed to mark the closure area and protect public health and safety, cultural and natural resources, scenic values and scientific research activities.
    • TRRP will notify local neighborhoods and work to minimize the impact of trucking on their neighborhoods. Trucking speeds would be kept slow and hauling schedules would be timed to minimize residential impacts. If used, County or private roads would be maintained, and public safety would be supported by signage and other safeguards.
    • A fish biologist will monitor for active redds and turbidity will be checked throughout the operation. If water cloudiness exceeds permit limits, work will pause. Equipment used in-river will use biodegradable hydraulic fluid to protect water quality.

If you have questions, concerns, would like to be placed on a notification list, or want to learn more about the project please contact us at:

Click here to read more about why the program uses sediment and wood augmentation as a restoration tool on the Trinity River.

Click here to read more about Sediment and Wood Augmentation Projects.

Further Information