Levee failure along Washington’s Green River highlights flood and ground stability risks during atmospheric river events

A levee breach occurred along the Green River near Tukwila, Washington, during renewed atmospheric river rainfall that affected the Pacific Northwest in mid-December 2025. The failure took place along the Desimone levee, a critical flood protection structure designed to reduce risk for communities including Tukwila, Kent, and Renton. At the time of failure, the Green River water level had risen to nearly 22 feet, following a rapid increase of approximately 15 feet over one week. This level exceeded observed river stages recorded over the past six decades. Flash flood warnings were issued for more than 45,000 residents, and evacuation notices were implemented in low-lying areas east of the river.

The breach occurred under prolonged high hydraulic loading associated with successive storm systems. Prior to failure, emergency seepage control measures had been installed to address internal erosion risks within the levee embankment. Despite these interventions, floodwaters removed a section of the levee, creating a localized opening comparable in size to a passenger vehicle. Emergency repair operations were rapidly deployed, including placement of large sandbags and temporary fill to stabilize the embankment and limit further erosion. By early evening, the immediate flood threat was contained, and warning notices were lifted as river levels stabilized.

The incident occurred while Washington state was still recovering from widespread flooding caused by an earlier atmospheric river. Continued rainfall, elevated groundwater levels, and saturated foundation soils increased susceptibility to levee instability and slope failures across the region. Forecasts indicate additional storm systems may further delay recovery efforts. The event underscores the importance of continuous geotechnical monitoring, seepage control, and adaptive flood defense strategies for aging levee systems subjected to increasingly frequent extreme hydrological events.