Sims: Predictions of warmer, wetter winters heighten need for flood-protection upgrades

With global warming experts forecasting wetter winters and more periods of heavy rain that could lead to higher stream flows, King County Executive Ron Sims says now is the time to invest in strengthening King County’s aging flood-protection infrastructure.

A new report, “Climate Change Building Blocks,” highlighting the relationship between global warming and the potential impacts on the Puget Sound region was released this month. The report is authored by members of the University of Washington’s Department of Civil and Environmental Engineering and the Climate Change Technical Subcommittee, which is part of the regional water supply planning process.

Thirteen climate change “building blocks” are identified in the report, including changes in temperature, precipitation, snowpack and glaciers, streamflows and sea level rise, plus changes to salmon habitat and populations.

Scientists predict the effects of global warming will include increased winter flows in snowmelt-fed river systems, which includes most of King County’s major river systems.  High flows over longer periods of time could damage the levees and other structures that King County relies upon to protect people and their property.

“Climate change is predicted to accelerate the hydrologic cycle due to increased evapotranspiration and increased storm events,” said Rick Palmer, who heads the University of Washington’s Water Resources Management and Drought Planning Group.

“We have already experienced increases in the quantity of winter rainfall, particularly in the month of November, a critical flood month. Forecasts for this region suggest that storm intensity will also increase.  The warmer temperatures associated with climate change in the late fall and winter will result in additional flood events due to more precipitation falling as rain rather then snow,” Palmer said.

"This report sends a clear message that we must upgrade our levees and other flood-protecting structures now – before the anticipated effects of global warming send our streams and rivers over the banks and into businesses and neighborhoods,” Sims said.

“Last winter’s stretch of heavy rain revealed several weak points in our flood-protection structures, many of which are near the end of their engineered lifespan,” he said. “Even without the anticipated effects of global warming, we know that the levees must be strengthened to keep citizens safe.”

King County maintains a levee system that runs along 119 miles of rivers, protects lives and property located in the 25,000 acres of floodplain in King County and more than $7 billion in economic infrastructure.

Sims has submitted a plan to the County Council that identifies a range of $179 million to $335 million in priority repairs and upgrades over the next decade, and recommends creating a countywide flood control district to fund the plan.

Under the recommendation, the owner of a $300,000 home in King County would pay from $15 to $30 per year, depending on how much of the priority flood protection work is funded.

Sims said the plan that he’s sent to the County Council will enable King County to catch up with the backlog of work that its aging network of levees desperately needs, while remaining fiscally responsible. The plan also calls for acquiring frequently flooded properties and expanding operations at the King County Flood Warning Center.

The County Council is expected to adopt the flood plan by the end of the year or early in 2007, and consider formation of the new countywide flood control district next spring.

Sims’ proposed flood-protection plan is available online at http://dnr.metrokc.gov/wlr/flood/fhmp/index.htm

The climate change report is available online at http://www.govlink.org/regional%2Dwater%2Dplanning/tech-committees/climate-change/index.htm

The Regional Water Supply Committee, which commissioned the climate change report, is a non-regulatory group of counties, cities, water district and other organizations that works together to manage their respective water systems and resources. More information on the Regional Water Supply Committee is available at http://www.govlink.org/regional-water-planning/index.htm