This story appeared in the Fall 2014 edition of Our Big Backyard, a quarterly magazine about parks and nature. Read more stories, plan an outing with a field guide, and find out more about fun nature events and classes.
Look at those rootwads! My eyes had just caught a glimpse of a large deck of logs with the rootwads still attached. I immediately started thinking about how to acquire those logs. Large pieces of down wood with rootwads are one of the essential habitat features in our streams – think of them as part of the furniture of great salmon habitat.
A healthy stream system has riparian areas with trees of many sizes, including some big old ones that will fall into and get caught up along the streambank, creating shelter for insects, salmon and other native fish and wildlife. Most of the urbanizing streams in the metro area have lost those large trees to farming, development, and other land use changes.
Books have been written about how to restore our streams, and distilling the best science comes down to thinking about stream restoration as a three-legged stool. The first and most important leg is to protect and connect the existing good habitat. The next leg is to restore habitat-forming processes that shape habitat, and the third leg is to create habitat features in streams and floodplains.
Johnson Creek, in east Multnomah County, is one of the streams where Metro and our partners are focusing our stream restoration efforts. Research has shown that the watershed's health suffers from isolated floodplains, lack of plantings along the banks and low levels of large wood. Since 1995, Metro has acquired more than three miles along Johnson Creek and its tributaries, creating new natural areas and helping to connect habitat with other protected lands – remember leg number one: protect and connect.
We’ve planted tens of thousands of trees and shrubs as part of our effort to restore the habitat-forming processes along the stream. The young trees will be large trees that eventually fall into the stream and become fish habitat. There is leg two: restore ecological processes.
And this summer, I was part of a team creating large wood jams along about a mile of stream in the upper Johnson Creek watershed – leg three: create habitat. Research about Johnson Creek has suggested that thousands of large pieces of wood existed in the riparian forest prior to development. Our project is just a small start to adding that important furniture back into the system.
Creating fish habitat along a stream bank is messy. It starts with an engineered design, and then moves into the art phase as work begins to fit the engineered plan into the natural world. In order to create large wood jams, you need a lot of big logs with their roots attached and large equipment, such as excavators and dump trucks, to move them around. The gritty work includes dragging logs to the stream and excavating holes along the stream bank to bury wood and boulders, which will slow and push floodwaters back up onto the floodplain as well as help create the shaded alcoves for salmon to shelter in.
These types of stream restoration projects have to be done in a narrow period of time and during the driest part of the year to reduce negative impacts to water quality, fish and wildlife. typically, the words "delicate" and "excavator" aren’t paired. However, in stream restoration, there is no other way to describe the contractor's work of gently placing wood and rock along a stream bank to create a natural looking and fully functional log jam. Ecologist + engineer + fish biologist + excavator operator + humility = improved fish habitat.
Protecting and connecting habitats and restoring natural functions within a watershed give us the best long-term return for watershed health. Those actions take time, and as we work on those opportunities, the log jams help provide an immediate pulse of good spaces for our native wildlife.