Rock Weirs as Tools for Stabilization in Restoration Projects: An appraisal and comparison of two stream restoration projects in Northern California
Rock weirs and root revetments were the main structural components in two San Francisco Bay Area creek restoration projects completed in the 1990's: Uvas Creek in the South Bay and Wildcat Creek in the East Bay. David Rosgen assisted in the design of both restoration projects and the similarities between the two designs are striking considering the differences in size, sediment load, setting and general circumstances of the projects. The two projects have reacted differently in the time that has passed since project completion. In Uvas Creek, which is alluvial in nature and confined in a wide valley, all of the weirs have been buried washed-out, or abandoned by the channel. Topographic surveys of Uvas Creek revealed that the Creek has aggraded across its floodplain, depositing approximately two to three feet in some locations. In Wildcat Creek, which is constrained in a narrow valley, 70 percent of the weirs persist and have created a forced-pool morphology. While rock weirs in Wildcat Creek have added complexity to the channel, and therefore improved the channel from a habitat and aesthetic standpoint, they have not successfully stabilized the creek. Drawing from the study of these two creeks, it seems that rock weirs are not effective in channel stabilization.