Then, between 1963 and 1964, the Sammamish River was dredged by the U.S. Army Corps of Engineers (Corps) to reduce flooding to farm lands lining the Sammamish River valley.  Rounding out these impacts is the fact that the entire watershed continues to experience tremendous growth in development and urbanization.

Data collected by the U.S. Geological Survey (USGS) has regularly recorded the levels of Lake Sammamish since 1939.  Since construction of the Corps’ Sammamish River flood control project, there has been a dramatic decrease in the average winter water surface elevation of the lake, as depicted in the graph below.  

Despite the flood control measures of the last century, many residents do not recall the high lake levels of the past, and each new high water event triggers questions about whether the lake levels are progressively rising, and if so, what would be the cause.  The data shows that, statistically, lake levels have not really been rising. 

Invasive Weeds Presentation

You are invited to a presentation concerning invasive weeds to be given at a meeting of the West Lake Sammamish Association (WLSA).  It will be held at:

  7:00 pm Wednesday, March 28, 2007

Vasa's Ballroom (near the south end of W. Lake Sammamish Pkwy. (across from Vasa Park - look for sandwich signs).

A member of the King County Lake Stewardship Program will make the presentation.

Lake Sammamish daily average water surface elevations, 1939-2007

More recently, however, two things have changed: 

(1)  Expanded data and modeling capabilities have shown that vegetation is only one of many factors affecting flood flows, and clearing at that scale may not be warranted; and

(2)  Historic clearing along the riverbanks has been identified as a factor contributing to the decline of native salmon and other riverine fish and wildlife species, and wholesale clearing is typically no longer permitted.  

As a result, management of this flood control facility has shifted in focus from a single objective towards practices that support multiple benefits in this resource-rich area. 

For about a decade beginning in the early 90’s, vegetation cutting was significantly reduced as King County and the Corps re-evaluated these practices in light of both flood control and habitat protection needs along the river.  In 2002, the agencies agreed on a less damaging approach, and the County has performed this modified vegetation management regime since that time.  It is recognized, however, that this is a temporary measure that will be employed only until a more permanent solution can be crafted. 

In order to meet the many needs of this important area, King County is developing plans to modify the Willowmoor Reach of the Sammamish River to further improve in-stream and riparian corridor habitat conditions while protecting the long-term maintainability of the original projects’ flood control benefits. 

The Transition Zone will be reconfigured to allow for greater conveyance and storage of floodwaters in the adjacent floodplain areas while increasing both aquatic and terrestrial habitat features such as vegetation, downed large wood, and in-stream pools.  An improved connection with a tributary stream will be constructed and a remnant, but degraded wetland will be restored.  The area will be restored both functionally and aesthetically for many diverse uses, including passive recreation; environmental education; river, floodplain, and wetland functions; and terrestrial wildlife corridors and flyways. 

The primary purpose of the project is habitat restoration, but the project may provide additional flood benefits.  At a minimum, current levels of flood protection, as established by the Corps’ original project, will be maintained if not improved. 

SLS Notes . . . 

SLS has concerns about the increased in-flow into the Lake during the winter.  Historically, the large volume of rain in the Sammamish watershed (nearly twice the 35 inches a year that falls on Seattle), has been absorbed by the surrounding forests.  Like a well-regulated reservoir, loose, sponge-like forest soils retain and then slowly release stored rainwater into the aquifer and surface streams.  Such a natural system prevents flooding in winter but continues to supply clean, cold water to streams and aquifer in the dry months.

Where forests have been replaced by impervious surfaces -- roofs, roads, parking lots of surrounding new businesses, and housing developments -- the loss of rain storage capacity as well as a more rapid rate of runoff, can lead to flooding.  Thus, we have a condition where:  (1) the volume of rain hitting the ground is doubled, and (2) the rate at which it reaches the Lake is also increased dramatically.

Rain hitting Lakemont Fire Station or Skyline High School, for example, will reach the Lake in a matter of hours via surface flows, rather than in months via percolation through the soils and ground water.

SLS compares the situation to a bathtub with one drain.  With the normal two faucets pouring water into the tub, the water level can be controlled.  But if more and more faucets are added, with still only one drain, the tub can overflow quickly.

As the surrounding area urbanizes, the community must decide what to do with Lake Sammamish.  A lake reflects its watershed. Conversion of the watershed from forests to cities causes deterioration of water quality. That means the problem is us--everyone who lives in the watershed or even drives through it! Clearly we all have to be part of the solution.

  General channel definition has been lost – the Creek bottom is flat - due to massive sediment deposition.  Pools that had been formed by water swirling around big tree-root wads, have been filled in.  Logs across the channel that had been bridges two or three years ago, became dams last year and are now virtually buried under the sediment.

  The mouth of Lewis Creek has moved to the north. The previous outflow to the west was blocked by sediment the Creek transported during the 2005/2006 winter.  The channel at the mouth is not well-defined; it is very shallow and sandy.  Great Blue herons, bald eagles, cormorants, terns, and crows stand guard and have easy pickings of the returning kokanee.

  Significant bank erosion has occurred below the 185th Street SE Bridge.

  Part of a sandy bank (approximately 35 ft. x 20 ft.) upstream of 185th Street bridge has been undercut by the high flows and has collapsed into the Creek.  Clearly, this was a source of some sediment downstream.

  A gabion rock retaining wall behind houses on 185th Place SE is bulging ever further over the stream, particularly at the upstream end.  The Creek continues to undercut it.

  Some rip-rap armoring, a home-owner’s attempt to protect property from erosion, was moved by the flows. 

  Trees and bushes cleared from stream banks have made those areas more vulnerable to erosion and increased muddy runoff into the Creek.

The State of Washington was to develop a control program.  However, we have learned there is currently no funding for a regional effort.  

The Federal USDA Wildlife Services has contracted with two local jurisdictions (Skagit County and Vancouver, WA) to trap nutria, and is prepared to extend the effort if funding was provided at the Federal, State, or local level.

Nutria

Their method is to trap them in floating traps, and then euthanize them.

A regional effort is best because the nutria migrate from one body of water to the next. 

Please contact your State congressional representatives and ask that funding be provided to eradicate this invasive species. 

Thank you to all who submitted some great ideas for a tag line for SLS.  The Board had a really tough time coming up with the winner.  After much discussion, the winner is:

Save Lake Sammamish – and we all win!

The winning entry was submitted by Penny Short of Sammamish, and she is shown in the accompanying photo enjoying a cup of coffee and holding the prize for the winner, a certificate for six months worth of Starbucks coffee beans of the month.

You can see we are using the tag line liberally in this newsletter.  We also have incorporated it in the SLS logo, and are using it in the signature block of E-mails and letters.

Penny Short – Her tag line says it all!