An update to the King County floodplain maps will be presented to residents at two upcoming public meetings.
Floodplain maps are used, among other things, to adjust flood insurance rates for landowners within them. They are created by the Federal Emergency Management Agency (FEMA) with help from local jurisdictions.
Ken Zweig is the program manager for King County River and Floodplain management and said the main changes involve boundary adjustments.
“We just have better information available to us now,” he said. “…By having that longer record, we’re actually able to produce better maps.”
The last time some areas of the map were updated stretches back decades. As topographic, water flow and hydraulics data is collected, it is applied to more accurate maps.
Zweig said there have been 12 presidential disasters related to flooding since 1990 in King County that have had significant impacts on the county.
Every major river system in the county can experience flooding and this map update affects the Cedar, Mill Creek, Black, Sammamish and Green River systems.
“All of our major rivers have some history of flooding,” Zweig said.
According to the FEMA website, a number of factors determine the rate of flood insurance for people located within floodplains.
These include the amount of coverage purchased, the deductible, and the location, age and type of buildings.
Every jurisdiction has different regulations surrounding construction and land uses on floodplains, Zweig said.
The updated map will also inform planning, permitting, construction and the understanding of flood risks in given areas.
The updates generally reassessed the 100-year floodplains, meaning there is a 1 percent chance they will flood in any given year.
Some floodplains include one starting in North Bend and running northwest through Duvall into Snohomish County.
Others include areas of Kent, Auburn and the Skykomish River Valley.
Part of the county’s flood prevention efforts include educating people and a flood warning center that opens during floods.
Levies and other projects are also in the works to better protect communities from floods.
The first of the public meetings will be held from 5:30-7:30 p.m. March 20 in the banquet room of the Renton Community Center.
A second meeting will occur the following day from 6-8 p.m. in the Kent City Council chambers.
Floodplain managers from various jurisdictions will be able to answer questions for residents.
According to a county press release, homes within a high-risk flood area have a 26 percent chance of being flooded over the course of a 30-year mortgage.
Flooding isn’t unique to King County as areas in southwest Washington regularly experience floods.
A notable example was the 2007 flooding in Lewis and Thurston counties that submerged several communities.