How Mount St. Helens eruption still impacts local waterways decades later

The eruption of Mount St. Helens in 1980 released an estimated 3. 3 billion cubic yards of earth, resulting in substantial sediment flow into the Toutle River and the Columbia River. In response, the U. S.

Army Corps of Engineers initiated a sediment management plan that includes building a sediment retention structure to reduce flooding risks, particularly for communities downstream. Current sediment flow from the Toutle River is approximately a million tons annually, which poses significant challenges for cities like Castle Rock, Kelso, and Longview. Emergency Management Director Larry Hembree explained that silt buildup has eroded riverbanks and disrupted local water supply systems, necessitating changes to how water is sourced. The Corps' sediment management strategy comprises three main components: constructing retention structures, raising levees, and conducting spot dredging. These measures are designed to manage sediment movement effectively over a planned horizon that extends to 2035.

The ongoing erosion and sedimentation issues highlight the lasting impact of the eruption on local infrastructure and ecosystems. As sediment continues to flow, local authorities remain vigilant in adapting their strategies to mitigate flood risks and protect community resources.