Chehalis Floods: When Interstate Five Goes Underwater
Washington
Interstate Five is the spine of the West Coast, connecting California to Canada in a near-continuous thread of asphalt. It has been closed in earthquakes and ice storms. But the most reliable threat to this corridor sits right here in the Chehalis River valley, where a modest river has learned to shut down the country's most important highway with disturbing regularity.
The Chehalis River drains a broad basin in southwest Washington's Coast Range, and its floodplain reaches directly across the freeway corridor between Chehalis and Centralia. In nineteen ninety, nineteen ninety-six, two thousand seven, two thousand nine, and two thousand twenty-two, major floods have closed the interstate, the parallel rail lines, and US Highway Twelve, effectively severing land connections between western Washington and the rest of the country.
The two thousand seven event was catastrophic. A Pineapple Express weather system, a river of warm Pacific moisture flowing in from Hawaii, dumped extraordinary rainfall on snowpack in the watershed. On December third, two thousand seven, a twenty-mile stretch of Interstate Five closed between exits sixty-eight and eighty-eight. At one point, the roadway at Exit Seventy-Seven sat under fourteen feet of water. The closure lasted four days. The economic disruption ran into the hundreds of millions of dollars.
Two years later, nearly the same thing happened again.
State and federal agencies have spent years debating flood control options, from dams to bypass channels to managed floodplain restoration. The Chehalis Tribe, whose ancestral lands span this basin, has been part of those negotiations, arguing that the river's behavior reflects a watershed that has been logged, paved, and diked over more than a century of industrial use.
Scientists note that five of the largest floods in recorded Chehalis history have occurred in the last thirty years, a pattern consistent with intensifying atmospheric rivers under a warming climate. The highway reopens. The river waits.
