Detailed planning and design, followed by thoughtful
construction projects, have begun to tame the stormwater menace in
Clear Creek, an important salmon stream that runs through
Silverdale in Central Kitsap.
A renovated stormwater pond at
Quail Hollow near Silverdale includes a walking trail and enhanced
wildlife habitat. // Photo: C. Dunagan
Stormwater has been identified as the greatest pollution threat
to Puget Sound. In Kitsap County, many folks believed that the
dense development pattern in and around Silverdale has doomed Clear
Creek to functioning as a large drainage ditch for runoff into Dyes
Inlet.
But reducing stormwater pollution is not beyond the reach of
human innovation, as I learned this week on a tour of new and
planned stormwater facilities in the Clear Creek drainage area. The
trick is to filter the stormwater by any means practical, according
to Chris May, director of Kitsap County’s Stormwater Division and a
key player in the multi-agency Clean Water Kitsap program.
Projects in and around Silverdale range from large regional
ponds of several acres to small filtration devices fitted into
confined spaces around homes and along roadways.
A giant piece of a cedar log stands erect in a barren landscape
north of Silverdale, where a new channel for Clear Creek stands
ready to receive water.
An old cedar log was recovered
during excavation for a new channel for Clear Creek.
Photo: Christopher Dunagan
Well, maybe this channel won’t be entirely new. Designers
working to restore this portion of Clear Creek studied old maps.
They tried to align the new man-made channel to the meandering
stream that existed 150 years ago, before farmers diverted the
creek around their fields.
During excavation, workers uncovered buried gravel — remnants of
the old streambed — along with chunks of cedar that had lain along
the edge of the stream. Buried and cut off from oxygen, these
pieces of wood survived for decades underground, while cattle
grazed in the fields above.
Workers excavating for the new channel used their heavy
equipment to pull out what remained of a great cedar log. They
stood the log vertical and buried one end in the ground — a
monument to the past and future of Clear Creek.
A restored Clear Creek
floodplain (before plantings) north of Waaga Way in Central
Kitsap.
Photo: Kitsap County Public Works
Chris May, manager of Kitsap County’s stormwater program, showed
me the new channel this week. He said it was rewarding to uncover
some buried history and realize that the stream would be restored
in roughly the same place.
“We found the old channel,” Chris told me, pointing to a deposit
of gravel. “We are pretty confident that we got it right.”
This $3-million project has been conceived and designed as much
more than a stream-restoration project. The elevations of the land
around the stream have been carefully planned so that high flows
will spill into side channels and backwater pools. That should
reduce flooding in Silverdale and help stabilize the high and low
flows seen in Clear Creek.
Before photo: This was the farm
field as it appeared before restoration. // Photo: Kitsap
County Public Works
The engineers did not calculate the reduced frequency of
flooding, but floodwater storage is calculated to be 18.4
acre-feet, the equivalent of a foot of water spread over 18.4 acres
or 29,700 cubic yards or 6 million gallons.
In all, about 30,000 cubic yards of material have been removed
across 21 acres, including the former Schold Farm on the west side
of Silverdale Way and the Markwick property on the east side.
Native wetland vegetation will be planted along the stream and in
low areas throughout the property. Upland areas will be planted
with natural forest vegetation.
The topsoil, which contained invasive plants such as reed
canarygrass, was hauled away and buried beneath other excavated
soils to form a big mound between the new floodplain and Highway 3.
That area will be planted with a mixture of native trees.
Graphic showing area before
restoration.
Graphic: Kitsap County Public Works
Plans call for removal of 1,500 feet of an existing road with
upgrades to two aging culverts. Adding meanders to the straightened
channel will create 500 feet of new streambed that should be
suitable for salmon spawning.
Plans call for adding 334 pieces large woody debris, such as
logs and root wads to the stream. Some of that wood will be formed
into structures and engineered logjams to help form pools and
gravel bars.
Graphic showing area after
restoration. Notice stream meanders near beaver pond habitat
Graphic: Kitsap County Public Works
“This will be one of the first streams to meet the Fox and
Bolton numbers,” Chris told me, referring to studies by Martin Fox
and Susan Bolton of the University of Washington. The two
researchers studied natural streams and calculated the amount of
woody debris of various kinds needed to simulate natural
conditions, all based on the size of a stream. (Review
North American Journal of Fisheries Management.)
The elevations on the property were also designed so that high
areas on opposite sides of the stream would be in close proximity
in several locations.
“Beaver will pick that spot,” Chris said, pointing to one
location where the stream channel was squeezed by elevated banks on
each side. “We want to encourage beaver to come in here.”
Beaver ponds will increase the floodwater storage capacity of
the new floodplain and provide important habitat for coho salmon,
which spend a year in freshwater and need places to withstand both
high and low flows. Because the county owns the flooded property,
there won’t be any complaints about damage from beavers, Chris
noted.
Aerial photo showing project
area with Silverdale in the background, Silverdale Way to the left
and Highway 3 to the right. // Photo: Kitsap County Public
Works
Clear Creek Trail (PDF 390 kb), which begins on the shore of
Dyes Inlet, will be routed along the higher elevations as the trail
winds through the property. Three new bridges will provide vantage
points to watch salmon after vegetation obscures other viewing
areas from the trail. Viewing platforms, as seen along other parts
of Clear Creek Trail, were not included in this project but could
be subject to further discussions.
Count me among the many people — experts, volunteers and users
of Clear Creek Trail — who are eager to see how nature responds
when water (now diverted) returns to the new stream channel. For
decades, the lack of good habitat has constrained the salmon
population in Clear Creek. The stream still has problems related to
its highly developed watershed. But now a series of restoration
projects is providing hope for increased coho and chum salmon and
possibly steelhead trout as well as numerous other aquatic
species.
In a story in the
Kitsap Sun, Reporter Tristan Baurick described work this week
on the Markwick property, where fish were removed in preparation
for final channel excavation.
Here are some details (including photos) of various Clear Creek
projects, as described in the state’s Habitat Work Schedule for
restoration projects:
