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River Planning
River planning includes ongoing activities
and preparation of special studies. The following are examples:
Gravel Removal Study
A gravel removal study is being conducted in parts of the Snoqualmie
River Basin. The purposes of the study are to characterize existing
sediment accumulation and flooding conditions, and to evaluate
the effectiveness of gravel removal for flood reduction in each
of five specific study reaches in the Snoqualmie basin. These
specific study reaches are the South Fork Snoqualmie River near
North Bend, the lower Raging River through Fall City, the Raging
River Delta and nearby mainstem Snoqualmie, the lower Tolt River,
and the mainstem Snoqualmie near Carnation.
This evaluation of gravel removal is being
done in response to community concerns that sediment accumulation
causes flooding to worsen in these specific study areas. Historic
responses to such sediment accumulation has included dredging
(excavation across the full wetted channel) and gravel bar scalping
(excavation only from the tops of gravel bars during the dry
season). The study characterizes existing patterns and rates
of sediment accumulation primarily by matching recent channel
surveys to past surveys in the affected areas. Various gravel
removal scenarios such as dredging or bar scalping are evaluated
by hydraulic modeling. Alternatives to gravel removal, such as
setting back existing levees, are also evaluated. Potential flood
reduction is shown by comparison of existing conditions to dredged,
bar-scalped, or levee setback scenarios. Anticipated impacts
of all scenarios are described.
The listing of some salmonid species as
threatened under the Endangered Species Act may affect the likelihood
of using gravel removal for flood reduction, due to the impacts
of gravel removal to salmonid habitat. The Snoqualmie River gravel
removal study will be completed as intended, to address community
concerns, and because the technical analyses of flooding, sediment
deposition, and effects of various channel modifications will
be useful for ongoing river management purposes regardless of
whether such management includes gravel removal. Affected resource
agencies, local jurisdictions, and tribes have been apprised
of this study during its preparation. Beyond this study, the
River and Floodplain Management Unit Section is committed to a channel
monitoring program that assesses sediment transport and accumulation
on a continued basis in selected reaches of the Snoqualmie River
and parts of other major rivers in King County.
Forum and WRIA Coordination
River and Floodplain Management Unit has a lead role in WRIA 10, White River Watershed planning and participates in King County's Watershed Forums and the WRIA groups. FHRS staff work closely with the Watershed Coordinators and their interjurisdictional partners on Forum and WRIA efforts including: prioritization of watershed projects related to flooding, fish, and water quality; implementation of restoration projects; participation in the WRIA technical groups; and preliminary planning for WRIA conservation plans.
Flood Hazard Education
Flood hazard education efforts aim to educate the public about
the risks of living in flood-prone areas, steps they should take
to reduce flooding, and programs available to help them insure
properties against flood losses.
Complaint Response and Enforcement
Staff investigates complaints about flooding, channel migration,
severe bank erosion and logjams on a year round basis, and especially
during and immediately following flood events. During large floods,
two-person teams patrol flooded areas along the major rivers
to provide rapid response to flooding complaints and evaluate
whether logjams pose an imminent threat to public safety and/or
public facilities. Patrols also inspect County river facilities
for structural damage and other warning signs that indicate potential
facility failure that could adversely impact developed property
and off channel habitat.
Violations of King County sensitive areas regulations, including
floodplain regulations, are referred to DDES and/or other appropriate
agencies for enforcement. Urban drainage complaints such as water
quality problems and toxic waste dumping in unincorporated King
County are referred to the WLR Division Drainage Services Section
for investigation of potential violations of water quality codes.
Other localized drainage and/or flooding complaints are referred
to WLR Division's Drainage Services Section for investigation.
Water quality complaints found in Cities are referred to the
King County Trouble Call Coordinator, who will contact appropriate
officials to initiate resolution of the problem. Large spills
of toxic chemicals or petroleum products are referred to the
Washington Department of Ecology. Fish kills are referred to
the Washington Department of Fish and Wildlife.
Interlocal Coordination
Staff of the River and Floodplain Management Unit coordinate extensively with other King County agencies as well as numerous outside federal, state, local and tribal agencies on matters pertaining to floodplain management, flood control, and riverine and riparian habitat. The major coordination topics include:
Dam Operations: Participation in tabletop
exercises related to Dam safety, flood control, and fish habitat.
Flood hazard reduction policy and regulatory consistency with
the State Department of Ecology and DDES countywide; Snohomish
County, the Cities of Duvall, Carnation, Snoqualmie and North
Bend, and the Tulalip Tribes in the Snoqualmie basin; the City
of Renton and the Muckleshoot Indian Tribe (MIT) in the Cedar
River basin; the Cities of Auburn, Kent, Renton and Tukwila and
MIT in the Green/Duwamish basin; and Pierce County and the Cities
of Auburn and Pacific, MIT and the Puyallup Indian Tribe in the
White River basin.
WRIA coordination with federal and state natural resource agencies,
Counties, Cities, tribes and citizen groups in the Snohomish,
Cedar/Sammamish, Green/Duwamish and White River basins. Major
areas of coordination are habitat restoration projects and flooding
impacts on riverine and riparian habitats.
Technical assistance to DDES and federal, state and local agencies
regarding public and private development projects affecting floodplains;
as well as input and review of bank stabilization and vegetation
management guidelines prepared by other agencies, including the
Army Corps of Engineers, the U.S. Natural Resources Conservation
Service, and the State Departments of Ecology and Fish and Wildlife.
FEMA and the State regarding floodplain land acquisitions, home
buyouts and elevations, property owners request and applications
for letters of Map Amendment and Revision, and the federal flood
insurance program.
Fish habitat utilization research conducted by U.S. Fish and
Wildlife Service at bank stabilization sites in King County.
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