Chehalis Cottonwood Study

cottonwood tree

Overview The Chehalis Basin Strategy is a 10-year partnership of agency, tribal, and independent scientists, private landowners, utility managers, fishers, farmers, and foresters, and local leaders who are trying to educe the risks of severe flooding and stem the declines of salmon populations within the Chehalis Basin. The Strategy is considering multiple flood control options including the creation of a flood retention structure and storage reservoir, levees, and other improvements. The Strategy also includes a habitat restoration component to improve habitat functions within the Chehalis Watershed to improve the production of Chinook, Coho, and other salmonids. Because of the controversial nature of the flood retention structure and importance of fisheries resources in the Chehalis Basin, the Strategy has multiple state, federal, tribal, and local government stakeholders.

Our Role As part of the preparation for the National and State Environmental Policy acts (NEPA/SEPA) Environmental Impact Statements, Dr. Hough-Snee was the lead riparian ecologist on an interdisciplinary team of engineers and wetland scientists that evaluated the potential impacts of flood control flow-modification on riparian Western black cottonwood habitat within the Chehalis River Basin. In this work, Dr. Hough-Snee paired hydrologic data, 1D and 2D hydraulic models, and remotely-sensed vegetation data and aerial imagery to map cottonwood stands and sandbar recruitment habitat. With this habitat map, Dr. Hough-Snee then performed statistical and spatial analyses to quantify how flow regulation from a proposed dam operation would impact floodplain inundation, sediment transport, and mature forest rewatering and seedling establishment. Dr. Hough-Snee was also the lead author of the resulting report submitted as part of the related SEPA technical documents.

At A Glance

Client Type
Prime Consultant and Public Agency


Project Timeline
2018 to 2019

Service Area(s)

Project Manager: Nate Hough-Snee, PhD, PWS