Large Wood

Large wood helps create healthy streams for both humans and wildlife.

The benefits large wood provides:

    • Large wood provides a source of nutrient inputs to streams and rivers – aquatic bugs eat and live on wood, these bugs then become food juvenile salmon and other fish.
    • Large wood holds fine sediment by slowing the water down behind it. This creates clean gravels below the wood that make great places for salmon to spawn. Fine sediment can fill in gaps between gravels and suffocate salmon eggs.
    • As moving water flows around and over large wood in the channel, deep pools are scoured. These pools provide cold resting areas and cover from predators.
    • Erosion is a natural process for rivers, and the presence of wood in channels can either help stabilize a channel or can encourage erosion that creates river meanders, side channels, or braided channels.
    • Large wood helps increase the length of a stream or river which increases the capacity of a channel to hold water, thereby reducing flood impacts. During floods, large wood connects streams to their floodplain and provides flood water storage and an area for sediments to deposit.

While all of these functions are critical for a healthy stream system, sometimes large wood can create significant challenges for people living next to a stream or river. Eroding streambanks and channel movement can negatively impact farms and homes. You can learn more about erosion concerns and resources available for property owners here.

Rivers and streams in Puget Sound are suffering from a shortage of large wood. During the 19th and first part of the 20th century, people removed wood from northwest streams and rivers to improve navigation and control floods. During the same time, logging reduced the abundance of large conifer trees in the forest that were a source of large wood for waterways. The reduction of large wood in our streams and rivers has meant a decline in their ability to support fish and wildlife, and increased flooding and erosion.

The scarcity of large wood in Puget Sound streams and rivers is one contributing factor to declining salmon populations and habitat restoration and salmon recovery practitioners are working to increase the amount of large wood in our waterways. These projects may involve the construction of log jams, placement of individual pieces of wood in the channel, or construction of structures that trap wood moving downstream.

The Snohomish Conservation District and many other organizations and agencies are working to restore river processes and recover salmon populations by improving large wood abundance in streams and rivers.

installed large wood

Installed large wood

large wood construction

Large wood construction

large wood in Japanese gulch

Large wood in Japanese Gulch

Large wood in creek

Large wood in creek

How can you help?

    • Leave wood in the channel. If you are concerned about how wood in your stream may impact your property, please contact a Habitat Restoration Specialist.
    • Plant native trees along your stream or river. These trees are a future source of large wood in the stream. In the meantime, streamside trees provide shade and many other benefits. Jump to Streamside Vegetation now.