For the past couple months, we've been planning a new project in the Hylebos. We're calling it the Spring Valley Restoration Analysis.
The Problem:
Hylebos Creek, just south of S 359th St, is depositing unusually large amounts of sediment into the stream channel.
This photo was taken in Feb 2007. When I started working for the Friends in 2005, the gravel bar on the left didn't exist.
This is the same location in December 2008. The creek is now flowing through the salmonberries on the right.
I was just at this site last week, and noticed that two cedar trees that were alive a year ago, are now dead, which I believe to be because their roots are inundated with water now that the channel has changed. This kind of instability also makes it easier for invasive plants to get established.
Here is failed structure #1. Once upon a time, the creek flowed over the logs. Unfortunately, whoever designed this structure, faced the V in the wrong direction. The downstream-facing V splits the stream, and it eroded the banks. This should have been an upstream-facing V, which would have collected any sediment on the edges, concentrated the flow in the center, and carved out a nice pool.
Our big plan for this section of Hylebos Creek is to do an assessment of the creek, so that we can more accurately know what kind of stream work it will take to fix these problems, a wetland delineation (which we will need for an Army Corps of Engineers permit), and a conceptual design.
We are also planning on doing a forest health assessment of the Spring Valley Open Space (54 acres), which will lead to a forest management plan and recommendations for future actions.