Issaquah Creek menaces homes, floods streets
December 14, 2010
By Warren Kagarise
City emergency responders turn attention to mudslides in aftermath
Rainfall gorged Issaquah Creek and menaced homes, businesses and roads Dec. 12, as a late-fall storm reminded emergency officials and residents to plan for a rain-soaked winter.
The deluge turned the creek into a roiling broth the color of chocolate milk and led to flooding on roads and in Issaquah neighborhoods.
City officials had not yet determined the extent of property damage the day after floodwaters receded.
Emergency planners and residents eyed Issaquah Creek as floodwaters spilled across Newport Way Southeast and lapped at the doorstep of Gibson Hall.
Residents reported street flooding from Montreux on Cougar Mountain to the business district along Northwest Gilman Boulevard to downtown Issaquah. Drivers also reported water flowing across Issaquah-Hobart Road Southeast in rural King County.
Crews responded to mudslides in Talus, after rain-soaked earth toppled onto Lingering Pine Drive Northwest.
City crews fanned out across Issaquah to unclog storm drains and clear debris as the deluge led to flooding in neighborhoods and caused the creek to rise. The task carried added urgency Dec. 12 as forecasters ratcheted up a flood watch to a flood warning.
The morning after Issaquah Creek crested, attention turned to potential mudslides on steep hillsides.
“The ground is now saturated and the creeks or drainage systems are full,” Bret Heath, city Public Works Operations and emergency management director, said Dec. 13. “It’s not going to take a lot more rain” to cause ground instability and possible mudslides.
Pineapple Express barrels in
The heavy rainfall and unseasonably warm temperatures stretched road crews less than a month after teams mobilized to clear snow and ice from city streets.
Meteorologists predicted late last week for a Pineapple Express system to dump 1 to 3 inches of rainfall in the lowlands and 3 to 8 inches in the mountains. (The phenomenon is so named because the moisture-laden system originates above the Pacific Ocean near Hawaii.)
Heath said the detailed forecast enabled city crews to prepare for the deluge and highlight potential problem areas.
Crews made 14 sand and sandbag deliveries in downtown Issaquah and along the East Fork. The teams also responded to numerous debris-clogged storm drains.
“The rest of it came in pretty much with what we expected in regards to forecast,” he said. “Obviously, when you have a lot of heavy rain like that, you’re going to get urban flooding, but as far as creek levels go, creek response, that was pretty much what we thought we were thinking we would be seeing with the weather forecast that we had.”
Chris Burke, a National Weather Service meteorologist in Seattle, said a National Weather Service spotter had recorded 6.05 inches of rain by 11 a.m. Dec. 12 in South Issaquah.
Heath and other emergency planners rely on real-time Issaquah Creek flood data from U.S. Geological Survey flood gauges in Hobart and near the creek mouth in Lake Sammamish State Park.
Though emergency planners monitor both gauges, only the Hobart gauge is used to determine flood phases in Issaquah.
La Niña could soak region
Forecasters said the gauge near the creek mouth recorded the water level at 10.6 feet at 4:30 p.m. Dec 12. The flood stage for the area is 10.5 feet.
The city did not activate the Emergency Operations Center for the flooding. Heath and other emergency planners received updates from the King County Office of Emergency Management during the flooding.
Eastside Fire & Rescue crews logged many hours in the Snoqualmie Valley, as the Snoqualmie and Tolt rivers spilled into neighborhoods and across roads.
Heath said the city response plan for flooding and a series of sediment-retention ponds performed according to plan.
Mayor Ava Frisinger climbed out of bed after midnight Dec. 12 to check data from the Issaquah Creek flood gauges.
“I’ve gotten so that any time it rains significantly in the night, I don’t sleep very much,” she said. “I’m thinking, ‘How many more inches more rain do we need before it turns into a giant flood event?’”
The mayor toured the city later in the day and met residents along the East Fork to discuss possible flooding.
The rainfall could prove to be a test for emergency responders. Forecasters predict a rain-soaked winter due to a return of La Niña conditions.
The city last experienced a major flood in January 2009. The natural disaster caused about $1 million in damage.
“Floods are nasty,” Heath said. “They cause problems for everybody and cleanup is a real headache.”
Warren Kagarise: 392-6434, ext. 234, or firstname.lastname@example.org. Comment at www.issaquahpress.com.