Streambank erosion is a natural process and, in an undisturbed stream, it usually happens slowly over time. Local rivers like the Molalla and Pudding are seeing their share of erosion, which effects fish habitat and water quality.
Clackamas County Soil and Water Conservation District wants to provide landowners some tools that may help with the issue. A streambank erosion workshop will be held Saturday, Sept. 20, from 8 to 11:30 a.m. at the End of the Oregon Trail Museum in Oregon City.
We are very lucky to have Janine Castro from the U.S. Fish and Wildlife Service and National Marine Fisheries Service in Portland, and Colin Thorne from the University of Nottingham, England, speaking at a workshop that is sure to fill quickly, said Lisa Kilders, information and outreach coordinator for CCSWCD.
Erosion is happening in and around the Canby and Aurora areas along the Molalla and Pudding rivers, said Kay Patteson, executive director of Molalla River Watch, and some simple techniques can help curb the erosion.
There is a lot of erosion going on and some of it is impossible to control, Patteson said. These rivers are naturally flowing rivers with no dams or anything on them. When it floods, it floods quickly. In that process, especially on banks that dont have a lot of vegetation on them, thats where serious problems occur.
When erosion happens, it sends a lot of sediment into the rivers and streams that feed into the Molalla and Pudding rivers.
That sediment eventually settles and it can smother gravel bars that are very important for fish spawning and rearing, Patteson said. It also creates a great deal of turbidity in the water as fish are moving through it. Its also a water quality issue. The city of Canby gets its drinking water from the Molalla River, so we want to minimize those effects as much as we can.
Some erosion caused property loss with large chunks of bank slumping and toppling into the stream following each large rain storm.
Whats the fix?
One way to help repair these serious erosion problems is to plant trees, shrubs and grasses in the area along the stream known as a riparian area. Healthy plants covering the stream banks and the area next to the stream will serve to protect water quality, provide habitat for fish and wildlife, and stabilize stream banks.
Creating a good, healthy buffer zone, even along smaller streams that people may think are only ditches but in the winter fill and bring water to the rivers, can help, said Patteson. Even those smaller tributaries can deliver a good amount of sediment into the river.
Some of the best shrubs for the riparian area are native willows like Pacific and Scoulers willow or Red Osier dogwood, which can be recognized by its bright red stems and small white flowers. Native trees to consider are Oregon ash and red alder.
Willows and dogwood form dense hedges with fibrous roots, which can greatly reduce water speed, in turn slowing down erosion.
The best time to plant trees and shrubs are when they are not actively growing, typically between November and March. If you live in an area with beaver, mice or other wildlife, it may be necessary to protect your plantings with tree protection tubes. Keeping the ground around each planting free from competing grass and other plants will also help reduce wildlife damage.
For more information on stream bank restoration in Clackamas County, contact Clackamas SWCD riparian specialist Jenne Reische, at 503-210-6011.
Workshops like the one coming up are really important for landowners along streams and rivers, said Patteson. They all contribute to the Molalla and Pudding rivers.