Green River Valley plans ahead for possible flooding

Green River folks are learning something about flood prevention from the people who live along the flood-prone Red River.

A delegation from Fargo, N.D., is meeting this week with officials of King County and four south county cities to explain how a massive volunteer effort and a coordinated government response succeeded this spring in holding back the highest water levels ever recorded on the Red River.

It's an important lesson because Kent, Renton, Auburn and Tukwila are facing possible flooding because of problems at the Howard Hanson Dam. The Army Corps of Engineers is limiting the amount of water it will allow behind the earthen dam, because water from its right abutment — the side of the valley against which the dam was built — is seeping at a fast pace. The corps wants to limit stress on the abutment until it can be repaired.

Less water behind the dam means more water will be released into the Green River during major storms until permanent repairs are made.

King County Executive Kurt Triplett said the Fargo visitors convinced him that the county and its partners can do more to protect the Green River Valley from possible flooding than officials had thought.

"Folks, this is a big deal not just for the citizens of King County but for the entire region and the state of Washington," Triplett said Wednesday at a news briefing at the county's Emergency Coordination Center outside Renton.

If rainfall is as severe this winter as it was last January, Triplett said, there will be "massive flooding" of a valley that hasn't had a major flood since the dam went into operation in 1961.

"We don't know if the Green River will flood this winter or next winter," Triplett said. "We are leaving nothing to chance. We will be ready."

Four officials from Fargo and Cass County, N.D., are briefing county and city officials this week on their experiences this spring. Cass County Emergency Manager Dave Rogness said 100,000 volunteers helped hold back the Red River by bolstering levees with 6 million sandbags in fewer than 10 days.

Most businesses in Fargo closed, giving their employees time off — in some cases paid — to fight the raging river. Residents of hospitals and group homes were evacuated to other cities and states.

South King County cities have been warning residents of the flood risk and plan to step up their efforts as the rainy season approaches. An estimated 15,000 homes and thousands of businesses are in flood-prone areas.

Tukwila Public Works Director Jim Morrow, who is incident commander for the flood-response planning by the four cities and the county, said evacuation plans are being coordinated among the cities, the State Patrol and the state Department of Transportation.

"The city of Tukwila did not want to be sending people south when the city of Kent was sending people north," Morrow said.

King County Emergency Management Director Robin Friedman told the Regional Planning Committee on Wednesday the county will declare an emergency as early as possible in the event of a flood to bring in federal and state help as fast as possible.

The county's Emergency Warning Center announced Wednesday it would monitor water flow from the dam rather than river levels at Auburn — a change that will provide the Green River cities seven hours' warning of rising water.

Keith Ervin: 206-464-2105 or kervin@seattletimes.com