Newly Published: Chehalis River Floodplain Geomorphic Mapping

We’re pleased to announce the release of a new publication!

Geomorphic mapping of the Chehalis River floodplain, Cosmopolis to Pe Ell, Grays Harbor, Thurston, and Lewis Counties, Washington

by S. L. Slaughter and I. J. Hubert

Relative elevation model of a portion of the study area approximately 5 miles east of Montesano showing the junction of the Chehalis River floodplain with the Satsop River.

Summary:  A relative elevation model of the Chehalis River floodplain was generated using 1- and 2-meter lidar and 12-inch-resolution aerial images in order to delineate subtle landforms on the floodplain for a 110-mile reach of the Chehalis River between Pe Ell and Cosmopolis, Washington. The relative elevation model represents elevation of features on the floodplain relative to the Chehalis River’s water surface by removing downstream changes in elevation associated with the channel gradient. Subtle landform features, such as primary, secondary, and abandoned channels, sloughs, swales, and natural and artificial levees were then identified within the floodplain. This information is useful to biologists, wetland scientists, land managers, property owners, and floodplain and watershed managers. The report contains 59 pages of maps at 1:28,000-scale and two pages of text.