ARLINGTON, Wash. — The Stillaguamish River and the Hazel Slide have been rivals for decades.
The river eats away at the clay and sand hillside to the north of the snaking river. Weakened by the erosion, the hill’s foot lacks the strength to fight the pull of gravity. Rain and logging add to the river’s offense.
In this deep-seated recess, landslides are inevitable. They send sediment surging into the river, deforming it for years until the cycle repeats.
This ongoing battle exploded Saturday in a...