A sophisticated analysis of sea-level rise in Puget Sound and
along the Washington Coast offers shoreline residents and land-use
planners a new map-based tool to assess potential flood hazards for
the coming years.
Click on map to access online
interactive map
Map: Washington Coastal Hazards Resilience
Network
Sea-level rise depends on two factors: how fast the oceans rise
and the rate of vertical land shifts. Uplift, such as what occurs
along the Washington Coast, slows the rate of sea-level rise
relative to waterfront property. Subsidence, which occurs in
Central Puget Sound, results in elevated tides sooner than in
stable or uplifting areas. One map on this page shows the measured
uplift and subsidence and another shows the uncertainty in that
measurement.
Ian Miller, a coastal hazards specialist at Washington Sea
Grant, has worked on studies that describe sea-level rise in Island
County and on the Olympic Peninsula. The new report, titled
“Projected Sea Level Rise for Washington State” (PDF 10.4 mb)
goes well beyond what he and his colleagues have done before. It
takes a more detailed look at where the land is uplifting and
subsiding, according to Miller, the lead author on the new report
that involves work by scientists at Sea Grant and the University of
Washington’s Climate Impacts Group.
Some of the highest tides of the year, combined with a strong
low-pressure system, could provide “King Tide” observers with ideal
conditions tomorrow (Monday) for taking pictures of near-flood
conditions or even flooding in some places.
This is the third year the Washington Department of Ecology has
put out a call for photos of high-tide conditions.
Photo of Poulsbo waterfront
taken during “King Tides” Dec. 28, 2011.
Photo by James Groh, Poulsbo
“Documenting how very high tides affect the natural environment
and our coastal infrastructure will help us visualize what sea
level rise might look like in the future,” states Ecology’s
“Climate Change” blog.
The King Tide photo initiative began in Australia in January
2009. Washington and British Columbia joined in 2010, followed by
Oregon and California in 2011.
Tide tables predict that tides in Bremerton and Port Orchard
will reach 13.4 feet at 8:28 a.m. tomorrow. Check on other
locations and other days in Washington state at Saltwater
Tides.
The National Weather Service has issued a coastal flood advisory
for Western Washington because of low-pressure conditions, which
could add 1.5 feet to the tide table prediction. That would put the
Bremerton area at 14.9 feet. Check out the
Weather Service advisory and the
Kitsap Sun story.
While it looks like we’ll have a very high tide, it probably
won’t be a record. I was unable to find historical data for
Bremerton, but the record high tide for Seattle is 22.4
feet on Jan. 27, 1983. The tide tables predict that Seattle
will reach 12.5 feet tomorrow, or 14 feet with the added 1.5 feet
because of the low pressure.
Shortly after I posted
this, Jeff Adams of Washington Sea Grant sent me an email to point
out that NOAA’s numbers need to be corrected by subtracting 7.94,
because NOAA uses a different baseline than we commonly use in this
area. That would place the record in Seattle at 14.5 feet, much
closer to what we may see tomorrow. I should have known that
something was amiss with that data. For more on this point, check
out Jeff’s blog,
Sea Life.
King Tides will continue through this week, declining slightly
each day, then will return on Jan. 14.
I’m certainly not hoping for high water levels, but where they
occur it would be great to have some photos. Feel free to send them
to me at cdunagan, as
well as uploading to the Flickr page called “Washington King Tide
Photo Initiative.”
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.
The Skokomish Watershed
Action Team (SWAT) surveys an area where the Skokomish River has
wiped out all vegetation and left a massive gravel bar.
Photo by Steve Zugschwerdt
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.”
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
Spot-dredge
Sediment trap
Culverts: a) add; b) remove; c) replace; d) upgrade
The Washington King Tide Initiative is entering its third year,
and state officials would like people to shoot photographs of
flooded roads, yards and buildings — if such events occur.
In 2010, the high tide at
the mouth of Gorst Creek comes close to reaching Toys Topless at
the head of Sinclair Inlet in Gorst.
Photo by Meegan M. Reid, Kitsap Sun
High tides are expected to continue for the next few days and
return to high levels again in mid-January. Whether flooding occurs
at any one place depends on rainfall, winds and atmospheric
pressure, as well as tidal levels dictated by the position of the
moon and sun. (See
NOAA Ocean Service Education.)
Not much flooding occurred during king tides last year, but
plenty of photographs were collected in early 2010. That’s when the
picture on this page was taken in Gorst between Bremerton and Port
Orchard. For additional photos, check out the Flickr page or the
video slide
show put together by the Washington Department of Ecology.
Taking note of these high tides is one way to gauge how climate
change may affect shoreline areas. Over the next 100 years, sea
level is expected to rise by at least 2.6 feet, according to the
U.S. Fish and Wildlife Service, although previous estimates by
the Intergovernmental Panel on Climate Change were in the range of
7 inches to 2 feet.
The King Tide Initiative started in Australia in 2009, according
to Ecology’s
website on King Tides, but it soon became a project for the
West Coast of North America, with Washington and British Columbia
joining in 2010 and Oregon and California joining in 2011.
For a list of high tides, go to Ecology’s King
Tide Schedule page and click on the map. More precise
information can be found on
NOAA’s page of tide predictions, where you can zoom in to your
area of interest.
