Chance of Flooding Decreased, Residents Jubilant but Vigilant

ELLEN M. BANNER / THE SEATTLE TIMES
Sandbags are lined up around the Green River to prepare for potential flooding.


The Army Corps of Engineers has been working hard to make secure adjustments and repairs on the Howard Hanson Dam and good news arrived last Friday...the chances of flooding have been lowered from a 1 in 3 chance to a 1 in 25 chance!

Since January, they've pumped a half a million gallons into the damaged abutment to hold back water during days of heavy rain. This last Thursday, Corps of Engineers Col. Anthony Wright said that it is, indeed, doing it's job. The grout bonded with earthen materials to slow seepage enough that he was able to increase the capacity of the reservoir behind the dam of about 33% to about 50% of its normal capacity.
Therefore, reducing the risk of causing forced flooding in the Auburn valley region to about 1 in 25 with an overall risk of 1 in 33 with the sandbags and other security features to be installed.

Col. Wright maintains, however, that if we again experience Pineapple Express (a series of storms carrying heavy moisture from the subtropics) like we did in January, he would have to cause flooding by releasing water from the dam.

The new numbers are are fantastic improvement, but residents are still staying on guard.

King County Executive Kurt Triplett stated "the new percentage sounds great, but the reality is we had just that type of storm event 10 months ago. I'm definitely going to be sleeping easier..., but we're not out of the woods."

When the dam is fully restored with a concrete wall built within the abutment, there will only be a 1 in 140 chance of flooding. This could be 3 to 5 years away.

4 Major Seattle Cities at Flood Risk

Renton, Auburn, Kent, and Tukwila run a large risk at being flooded this fall and winter after 40 years without a problem. The last was in December 1959 which flooded some houses up to their second floors.

The culprit is the flood-control dam on the Green River. The Army Corps of Engineers who built the Howard Hanson Dam cannot decipher what caused a 10-foot-wide, 6-foot-deep depression in an abutment to the rock and earthen dam, but see that it could be a catastrophic issue.

For now, the Corps will store less water behind the dam until engineers can figure out what caused the problem and how to fix it. To achieve this, essentially all rainwater from storms will be released into the Green River. This runs a risk of overwhelming levees that protect Renton, Auburn, Kent, and Tukwila.

Officials from the possibly affected cities, the Corps, and King County have been telling businesses and residents to buy flood insurance and have an evacuation plan.
"We need to prepare for a long-term possibility that over the next few flood seasons we may experience anywhere from significant to catastrophic flooding, depending on the event," said Dana Hinman, a Auburn city spokeswoman.

A larger number of homes and businesses could be hurt in flood-prone parts of Kent, where about 50,000 people work and 22,000 people live, said Mayor Suzette Cooke. She said the damaged abutment "clearly raises our level of concern" about levees downstream that haven't been certified as meeting federal standards.

There is chance that I-405 could be severely flooded, and Highway 167 and two main rail lines could be severed.

Although there is a good chance some repairs could be made by fall, people in these high risk areas need to put careful consideration into buying flood insurance.

Many don't realize, flood insurance does not go into effect for 30 days from the date written and the rates are all the same-- because flood is only offered through FEMA (Federal Emergency Management Agency). Also, it's important to note that during most catastrophic times, companies will put a "moratorium" on writing new policies. Therefore, you have to be prepared.


SAV-ON can quote and write flood insurance. You can get a quote by calling 1-888-867-2866, e-mailing info@sav-on.com, or filling out our Quik Quote Form.

Huge thanks to Seattle Times Newspaper