The Fain team assessed and defined the bankfull width of a channel to inform a culvert replacement project within the Skagit River floodplain. The team determined and measured the bankfull width of the channel in the field at the project site. They assessed the bed material and measured cross sections at each bankfull width crossing. The team also made general geomorphic observations at the site regarding channel characteristics and aquatic habitat presence at the site. Using this information, the Fain team determined a natural bankfull width for the site. Additionally, we updated a USACE HEC-RAS model and determined potential velocities during a 100-year event.