The Builder on the Lake » Lake Sammamish Water Level

Weir getting closer . . .

Dwight — Sat, 11 Sep 2010 14:20:15 +0000

]Jane Hague & Kathy Lambert with Dwight at the weir; this stone “rip rap” is still visible in the mid channel but is under up to a foot of accumulated growth and silt in the high flow channels which drain the lake in the winter months.

On Thursday, September 9 King County Council-members Kathy Lambert and Jane Hague and county hydrologists and engineers joined representatives from Dave Reichert’s office and the City of Redmond–as well as a number of concerned Lake Sammamish residents–to take a closer look at the weir and the area that was recently mowed. This meeting was a result of an earlier King County Flood Control meeting, and was scheduled by Council-member Lambert’s office.

Before the meeting I went out to the weir to set up a few visual aids. I set my laser level–which rotates a full 360 degrees–on top of the weir at a height of three feet. Then I followed the laser beam and tied flags at that height on the vegetation surrounding the weir. This illustrated how high the water gets at Elevation 29: a significant flood stage design level. It also demonstrated how much of this area is filled by the “wall of willows”, logs, root balls, tall grass, accumulated silts, and other debris.

My earlier posts discussed the record high water levels we had this spring. This meeting was a great opportunity to show the County areas where flows are running into accumulations of debris which are blocking flow and were never intended in the original design. I recently noticed what appears to be up to a foot of accumulated silts and turf like growth in the high flow channel. Perhaps years of accumulated materials has raised the channel, which has a direct affect on lake levels. One observation is that the left channel is about one foot higher than the right. They should be the same.

We discussed next steps, I suggested removing the obstructions in the high-flow channel, logs and debris at this critical location are inappropriate. If willows must by maintained just below the weir, then limbing the tangle of low branches so that water can flow more freely would be a step in the right direction. A fish biologist was also present, he pointed out that this kind of habitat promotes bass who devour salmon as they migrate out to sea.

County hydrologists are studying the situation and want to be sure they fully understand it before they recommend a course of action. I am concerned that we are about out of time, fall is in the air and forecasters predict a wet and cold winter. I am glad that the County staff are taking this seriously, and want to thank Council members Hague and Lambert for coming out and marching through brush, water, and mud to see it for themselves!

Sammamish River 1991

Dwight — Thu, 22 Jul 2010 16:33:50 +0000

This is the low flow channel July 15, 2010

[caption id="attachment_204" align="alignleft" width="824" caption="note the open low flow chanel and the mowed high flow area"][/caption]

A Look at Why Lake Sammamish is so High

Dwight — Tue, 29 Jun 2010 20:53:18 +0000

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If you’re wondering why the water level on Lake Sammamish is at an all-time high, take a look at this video.

In it you’ll see the area around the weir that sits between Lake Sammamish and the Sammamish River. This small area is the only outlet for Lake Sammamish. It looks like the vegetation below the weir is backing the water up over the top of the weir and restricting the flow at the outlet.

I have asked both King County Flood Control and the Army Corp of Engineers why the lake is so high this year; it will be interesting to see what they have to say.

Here is how one family is affected by the high water:

Dwight — Sat, 26 Jun 2010 20:00:34 +0000

Lake Sammamish High Water Levels-Unprecedented

Dwight — Sat, 26 Jun 2010 16:16:12 +0000

Many docks are underwater, July 4 parties are being canceled, and water levels on Lake Sammamish are more like mid-winter then early summer. Can you trust the recollection of old timers who say ” I have never seen anything like this in all my years”? Yes you can. The United States Geological Survey has daily records of lake levels that go back to 1939. I went back and looked at June 12 lake levels for those 71 years and we are at an all time high. In the last 45 years, since the weir was built to control the flow at the outlet of the lake, the June 12 level has averaged 26.37, two feet below this years June 12 elevation of 28.34. This is important because most docks on the lake are built for summer use at about elevation 27.00. Just a casual observation; 75% of the docks on the lake are underwater, many by more than a foot!

More to come,

Dwight