Flood control is no longer a primary objective of federal restoration work on the Skokomish River — but improving the ecosystem is likely to reduce flood problems for people who live in the valley.
We don’t need to be reminded that the Skokomish is the most frequently flooded river in the state. Although I’m not sure how soon another river might take over that dubious distinction, it’s easy to see that a lot of time and money is being spent to get the river back to a more natural condition.
The Army Corps of Engineers, known for massive projects such as dikes, dams and dredging, won’t be adopting those sorts of projects for the Skokomish River.
Jessie Winkler, Skokomish project manager for the Army Corps of Engineers, explained it this way:
“Clearly, flooding is a problem in the basin. But because of limited residential and commercial activity, it would be very difficult to justify a flood-control project. In order to be justified as a federal project, the economic benefits must be greater than the cost.”
For further explanation, check out my story in Monday’s Kitsap Sun.
The good news is that the Corps has not turned its back on the Skokomish. In fact, the river is considered so important to the Hood Canal region that the agency is considering some large-scale projects focused on environmental restoration — including possibly relocating Skokomish Valley Road.
Other interesting ideas include creating sediment traps to capture gravel in selective locations, relocating existing dikes to create a wider river channel, forming new side channels to relieve flow on the main river and even aeration pumps to boost oxygen levels in Hood Canal.
Many of the projects designed for ecological improvement will also reduce the flooding problems.
A report, scheduled to be released in late spring or early summer, summarizes all information collected so far in the $4.7 million study of the Skokomish River watershed. The report will cover current ecological conditions, future ecological conditions without restoration and a list of potential restoration projects — including preliminary design, estimated costs and ecological benefits, Winkler told me.
Potential projects are only conceptual at this point, though experts have begun to look at locations along the river where different types of efforts may be fruitful. Further study will narrow the list of to a plan to be submitted to Congress for funding.
The upcoming report will begin to explore which of the following actions are most likely to succeed in specific locations:
- Remove or breach levees/dikes
- Construct setback levees/dikes
- Create salmon spawning habitat
- Reconnect wetlands, side channels, backwater areas, and tributaries
- Substrate modification
- Install aeration or oxygenation system in Annas Bay
- Reconnect dendritic channels in estuary
- Large woody debris
- Engineered Log Jams
- Fish passable weir
- Channel stabilization
- Riverbed and wetland vehicle exclusion
- Enhance vegetation – riparian & estuarine
- Control invasive species
- Channel rehabilitation or new channel creation
- Selective gravel removal on gravel bars
- Sediment trap
- Culverts: a) add; b) remove; c) replace; d) upgrade
- Road modifications
- Rehabilitate bank lines
- Cool water diversion to Annas Bay