Green River flooding: What it means for Federal Way | Pete von Reichbauer

By Pete von Reichbauer, King County Council member

With flood season on the horizon (October through March), now is the time to prepare for potential flooding in the Green River Valley — and learn how it may affect you, no matter how high the elevation of your home or business.


Due to the unique topography of our region, our annual rainfall and our susceptibility to major flooding, King County is no stranger to natural disasters. Since 1990, there have been 11 federally declared flood disasters. Flooding affects every citizen in King County. Tens of thousands of King County residents commute through, live and work in, or own businesses in flood plains.

Protecting citizens and property from injury and damage by natural disasters is the fundamental role of government. In 2007, the King County Flood Control District was established to provide a proactive, regional approach to flooding as well as funding to improve the county's 500 flood protection structures. This investment is an example of proactive steps government has taken to help protect our region from billions of dollars in potential loss and damage.

In January of this year, a major storm damaged an abutment adjacent to the Howard Hanson Dam, which has diminished the effectiveness of the dam and increased the flood risk to the Green River Valley. The Howard Hanson Dam is the primary flood protection facility for the entire Green River Valley. Although levees exist along certain portions of the Green River, those levees were not designed to replace the protection provided by the Howard Hanson Dam.

The Howard Hanson Dam is located near the headwaters of the Green River and has protected the region’s manufacturing and distribution centers, public facilities, and over 30,000 homes since 1962. The dam holds back flood waters in the winter, provides fish enhancements in the summer, and preserves our region’s water supply year round. The U.S. Army Corp of Engineers, an entity of our federal government, owns, operates, and is responsible for maintaining and managing the dam.

The Corps is working diligently to complete construction on a massive interim barrier in the area where water has been seeping through. Although the Corps does not consider this to be a permanent solution, the barrier may allow the Corps to retain some additional water behind the dam. At the same time, the Corps is working on a long-term solution, which could take between three to five years to complete.

This means there will be a higher risk of flooding in the Green River Valley every flood season for several years.

King County is working with the Corps and surrounding suburban cities to alert the region to prepare for potential flooding and develop comprehensive response strategies. This regional collaboration includes establishing shelters in cities above the high water mark, developing alternative methods to transfer and distribute goods that would normally be processed in the valley, siting alternative transportation routes, and coordinating a civilian response unit to ensure there is sufficient manpower on the front lines if flooding occurs.

What does this mean for you?

The consequences of lowland flooding for residents at higher elevations could include power outages (gas and electric), water supply interruptions, interruptions to communications utilities (cell phones, Internet), and interruption in grocery store and other retail deliveries.

Additionally, impact to transportation is likely to extend beyond the inundation area. Depending on flood scenarios, disruptions to SR 167, I-405, and West Valley Highway could shift north-south traffic onto I-5 and Pacific Highway. This means we must plan for and expect an influx of traffic into areas such as Federal Way.

How to prepare

I encourage you to consider purchasing flood and sewer back-up insurance, which is not included with standard homeowner's insurance policies. You should also have a weather radio or battery powered AM radio on hand, have an adequate amount emergency food and water that will last longer than three days, and create a disaster plan for you and your family.

Think about all your daily activities: Getting kids to and from school, going to work, daycare, grocery shopping, and transportation routes you use throughout your day; these could be impacted.

What does this mean for the region’s economy or if you work in the valley? While 2 percent of King County’s total population lives in the flood plains of the Green River Valley, it is home to more than 65,000 jobs. The cities surrounding the Green River alone make up the single largest industrial area in the state. A one-day shutdown of floodplains in King County would cost the region $46 million in lost economic output, most of this from the Green River Valley.

If you work in the Green River Valley, check with your employer about procedures to follow if flooding occurs. Does your company have an emergency hotline to call? Can you work from home? Is there a satellite office you can work from? Does your office have an evacuation plan or emergency food supply? If you don’t know the answers to these questions, now is the time to ask.

As a community, we have persevered by working together, and as a region we must continue to help one another prepare. I am encouraged to see these partnerships move people to action. By preparing for the worst, we will all react and recover at our best.

Learn more

To obtain regularly updated information, go to www.kingcounty.gov/floodplans

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