Nearly 45 years after Mount St. Helens’ eruption sent almost 90 billion cubic feet of debris into the upper Toutle Valley, millions of tons of sediment still pour into the Cowlitz River each year.

What shapes these rivers, allowing them to nourish civilisations, and sustain life? Sediment. Sediments play a crucial role in the river’s health and ecosystem. Sediment dynamics influence the river’s ...