Surecatch,

There are several reasons the Skok blows out and floods more than almost any other river in our state.

1. Logging. Simpson Timber, through the Reed familiy's Republican political connections (sorry Aunty M) was able to secure a so-called "sustainable yield unit" permit, giving them the right to harvest U.S. national forest timber as though it was part of Simpson's private timberlands in the Skok watershed. The high harvest rates result in sediment loading that is greater than the ability of the river to flush it out to Hood Canal. Consequently, the river channel is aggraded (filled with fines, sand, and gravel), and has a reduced hydraulic capacity, resulting in over-bank flow every time discharge exceeds about 5,000 cfs, which isn't all that much water for the size of the basin.

2. Cushman Dams. The North Fork is dammed by Tacoma and contributes little water to the flooding ~ 60 cfs. Most North Fork water goes straight to Hood Canal via the powerhouse at Potlatch. The North Fork doesn't help flush sediments from the Skok either, but it likely couldn't anyway, due to the next set of problems.

3. Dikes and levees constrain the Skok to a too narrow river channel, so there is no where for high water to go except up and over the banks. And, as mentioned, it only takes 5kcfs to get there. To make the Skok a healthier river, the dikes need to be set back a ways, but that doesn't seem likely, as homes, barns, etc. would be displaced.

4. Highway 101 and other bridges. The bridge abuttments are too close together, causing a backwatering effect during every high water. The backwatering reduces stream velocity, and sediment deposits instead of being flushed out of the system. This keeps the river channel at a low hydraulic capacity, resulting in flooding at relatively low discharges. Each of the bridge crossings needs to be made about twice as wide as they presently are to accomodate higher flows and maintain stream velocity.

One could also blame nature. The compass aspect of the Skokomish watershed is positioned such that it receives very high precipitation across the entire elevation range. This leads to a somewhat higher cfs runoff per square mile of watershed, but this would be scapegoating.

Sincerely,

Salmo g.