Wetlands Capture Sediment and Expand Habitat
The 1980 Mount St. Helens (Lawetlat'la) eruption fundamentally altered landscapes, increasing downstream sediment flows more than four decades later. Managing the higher sediment loads using nature-based solutions has required regional, systemic efforts.
To mitigate the increased flood risks, diminished fish habitat, and other downstream burdens of higher sediment loads, the Lower Columbia Fish Enhancement Group (LCFEG) invests in nature-based restoration projects on the South Fork Toutle River.
In 2025, with support from the Ingrid Rasch Legacy Fund, Earth Economics evaluated the economic, social, and environmental benefits and costs of their restoration efforts. This detailed analysis illustrates the many benefits of such projects, and provides evidence to inform future investments.
A riparian and floodplain enhancement project in the Johnson Creek reach of the South Fork Toutle River (LCFEG).
Project benefits outweigh costs
We estimated the economic value provided by thirteen ecosystem services, including: flood risk reduction, carbon sequestration, habitat improvement, water quality improvements, and recreation.
Over three decades, floodplains restored by LCFEG projects are projected to generate $78 million in ecosystem service benefits, for a $30 million investment. Carbon sequestration, outdoor recreation, flood control, and water quality benefits contribute the most value to this total.
The project investments also generate substantial economic activity across Washington state. Construction-related expenditures are estimated to support $21 million in wages and nearly 400 regional jobs.
These nature-based solutions generate meaningful environmental, social, and economic value. These findings are informing future investments, including potential scaling of nature-based sediment retention strategies across the greater Toutle-Cowlitz watershed.
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