As flood season approaches, King County officials urge Pacific residents to sign up for its emergency notification system.
City Public Works Director Jim Morgan said Tuesday night during the White River Flood Forum at the Pacific Community Center Gym that Alert King County will replace Pacific’s Emergency Notification System.
Jeanne Stypula, King County supervising engineer, said anyone can sign up for that system for free online to receive voicemail, text or email alerts. According to the website, “the warning system provides at least two hours lead time before floodwaters reach damaging levels” in most locations. The website is here.
That is significant because Ken Brettmann, senior water manager for the U.S. Army Corps of Engineers’ Seattle District, said “the White River is losing channel capacity at a rapid rate.” He said in-stream flow was 20,000 cubic feet per second in 1948 compared to about one-quarter of that rate now.
He said that is problematic because the Mud Mountain Dam’s reservoir, which is 5½ miles long and can store 106,000 acre feet of water, can fill rapidly. Brettmann said the flood-control facility, which was built in 1948, was 40 percent full Feb. 18 after “moderate” rain in the preceding days. While the reservoir has never spilled over, Brettmann said that came within 15 feet of occurring in 1996.
With those challenges in mind, some residents questioned whether officials should remove sediment, which Brettmann said was the main reason behind the White River’s lagging in-stream flow, through dredging or gravel bar “scalping” to give it more room within the floodplain. But Stypula said that remedy is “expensive” and could present problems under the Endangered Species Act related to the river’s salmon population. Instead, work began in June on the Lower White River Countyline Levee Setback Project, which should be finished by December 2017.
That project, which is budgeted at $18.2 million and is out for bid, will construct a new, 6,000-lineal-foot setback levee along the landward edge of a forested buffer to protect existing properties and structures. A 5,000-lineal-foot, bio-engineered bank revetment also will be built along the existing wetland edge for the same purposes.
Stypula said a forested riparian buffer of about 17 acres will be restored adjacent to the wetland, too. That work, along with removal of the approximately 4,100-lineal-foot current levee and bank armoring, will reconnect the river with 121 acres of off-channel aquatic habitat for the first time in almost a century and reduce flood elevations in Pacific.
The Lower White River Right Bank Levee Setback Project is in the development stage, according to Stypula. That project, which she estimated will cost $25-30 million, would remove interim flood protection measures, such as the HESCO wall, and construct a setback levee along the Pacific Park boundary and adjacent residential areas on the right bank. Stypula said that project would significantly reduce the potential for flooding in those areas.
Even if those projects cost close to $50 million, Stypula said, they are expected to provide flood protection in the area for 50-75 years. Meanwhile, she said, dredging or other measures to remove sediment from the White River could cost $2-$3 million per year even if a permitting process, which could take years, shows “the need to do it.” Approval was granted earlier this year for a dredging project in the lower Cedar River in Renton.
