Abstract
A vegetation buffer located south of Yuba City, California was planted in late spring of 2011. The vegetation buffer was added to the water edge of a 29,400-feet-long segment of the Feather River Levee to increase wave attenuation and to provide 200-year protection to nearby communities. The vegetation buffer includes an existing walnut orchard and a section of planted riparian vegetation. The riparian vegetation included the following species: Arroyo Willow, Black Willow, Box Elder, Coyote Bush, Fremont Cottonwood, Oregon Ash, Sandbar Willow, Western Sycamore and Wild Rose. The original vegetation buffer was estimated to reduce wave heights from 4.35 feet to 2.78 feet based on a correction factor of 0.66. In this study, the Dalrymple formulation was applied to verify the wave attenuation for the vegetation buffer. The vegetation buffer had three sections along the levee that did not meet the design wave reduction of 2.78 feet. It is recommended that the riparian vegetation buffer of 41 to 131 feet be added to the vegetation buffer sections, which need to meet the design wave height. The correction factors calculated with the Dalrymple formulation for the walnut orchard and riparian vegetation are, 0.74 and 0.73, respectively. The original observed correction factor of 0.66 was not met. The correction factors should be specific to the site and vegetation buffer and this can be accomplished with the Dalrymple formulation.