Bursting rivers will test local dikes
Wednesday, January 7, 2009 9:11 PM PST
By Andre Stepankowsky
Printable version
E-mail this articleIf Castle Rock makes it through the night, the worst might be over, but South Kelso may be sweating it out for another day or two.
The Cowlitz was expected to crest at 55 feet at 4 a.m. Thursday morning, and at 25.65 feet in Kelso at 8 a.m. While those are among some of the highest river stages ever measured on the Cowlitz, they are below the levels recorded in November and February 1995-'96.
Nevertheless, the expected crests are seven feet above flood stage in Castle Rock and four feet above flood stage in Kelso. Weather service forecasters say the Castle Rock levee could fail, and officials still fear the Coweeman River dike may give way and flood South Kelso.
Incredible volumes of water gushing out of river basins Wednesday. The flow on the upper Lewis, for example, was forecast to peak at about 150,000 cubic feet per second — or more than half the average flow of the Columbia River at Astoria.
The big threat to South Kelso comes from the Coweeman River. Eyewitness reports had the river within a few feet of the levee crest near the Grade Street Bridge late in the afternoon Wednesday, and Kelso’s city manager and other officials estimated the chances were 50/50 that it could fail.
Monitoring the Coweeman is a challenge because it is not equipped with gauges, so the Weather Service does not track or forecast its rise and falls.
A boil developed Wednesday in the Coweeman levee at the Brook Hollow Mobile Home Park at the east end of the city. That prompted the call for evacuations in South Kelso.
Cowlitz County Emergency Management Director Grover Laseke said engineers would evaluate the boil this morning and recommend how to prevent it from breaching the dike. A boil is a spot where water is bubbling up through the levee because of the pressure of high river levels.
Elsewhere along the Coweeman, public works crews Wednesday built a berm across Coweeman Drive to shore up a low spot.
Rivers should be slowly receding into next week, as only intermittent rains are expected Thursday, with a good deal of sunshine in the forecast Friday, Saturday and into the middle of next week.
The Cowlitz rose sharply Wednesday after Tacoma City Light increased water releases out of Mayfield Dam to 40,000 cubic feet per second. The utility had been releasing as little as 9,000 cfs midday Tuesday from the dam, located in Lewis County.
Huge amount of runoff from the upper Cowlitz Basin were rapidly filling Riffe Lake, the utility’s 23-mile storage reservoir on the upper Cowlitz. The utility had no choice but to increase releases to prevent the reservoir from filling up, said Tacoma spokeswoman Chris Gleason.
Even with increased releases, Riffe Lake still was rising Wednesday. However, the utility does not expect any further increases in the discharge from its upstream dams, she said.
“We’re going to let (Riffe Lake) fill up as much as is responsible to do so to try to keep flows downstream as low as possible. But there is a point where it’s not responsible to let it fill any more. But we’re not anticipating going higher than 40,000,” she said Wednesday evening.
As recently as Monday, the utility had 66 feet of flood storage capacity in Riffe Lake, twice as much as its federal license requires for flood control. It still had about 26 feet of storage left Wednesday night.
Operators recently kept the reservoir drafted down as a hedge against a warm rain melting the low elevation snow that hit the area in late December, Gleason said.
“It was a preventive action on our part,” she said.
In Woodland, low lying areas outside the city might flood, and the airport along Interstate 5 and the city’s sewage plant also likely was likely to be inundated. The Lewis River at Woodland was expected to crest at 26.1 feet by Thursday morning. Flood stage is 24 feet.
Pacific Power, which operates three hydroelectric dams on the Lewis, announced Wednesday it will increase releases out of Merwin dam to accommodate runoff from the upper basin.
The upper Lewis was gushing with a flow of 150,000 cubic feet per second. That’s more than half the average daily flow of the Columbia River at it’s mouth. The flow , and it is even larger than the February 1996 storm, which caused widespread flooding in east Woodland and prompted a visit from then President Bill Clinton.
As of mid-day Wednesday, the Lewis River project still had approximately 30 feet of storage capacity available, well in excess of the 17 feet of storage required by federal authorities, the Portland-based utility announced.
tally ho wrote on Jan 8, 2009 12:58 AM:
Beer&Skittles wrote on Jan 8, 2009 8:19 AM:
Thought wrote on Jan 8, 2009 10:38 AM:
trikay77 wrote on Jan 8, 2009 11:28 AM:
lilsue62 wrote on Jan 8, 2009 2:38 PM:
grrrowl wrote on Jan 8, 2009 3:46 PM:
lilsue62 wrote on Jan 8, 2009 4:33 PM:
racingrocks wrote on Jan 8, 2009 6:08 PM:
grrrowl wrote on Jan 8, 2009 6:58 PM:
Building new dikes would cost millions and millions of dollars, to protect how many houses? Not to mention how many people that would probably be annoyed that they no longer had water views or some ridiculousness. The dikes were built in the early 1900's, It has flooded several times since then, it's not some crazy outlandish thing that hasn't happened in recent memory. It just happened in 1996! "
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