ONE YEAR OF BEAVER MODIFICATIONS TO A LARGE SANDY RIVER: A CASE STUDY IN CENTRAL CALIFORNIA

Beavers are well known ecosystem engineers that can dramatically change streams from simple channels into wetlands through the construction of dams and excavation of canals. The dams and canals enhance groundwater-surface water exchange and increase geomorphic complexity. Though beavers are more common in smaller streams, they also inhabit large rivers. It is often assumed that beavers build fewer dams and dig fewer canals, and therefore have a lesser impact on large rivers. However, we conducted a case study on the Salinas River in Central California and found that in one year a single colony of beavers significantly widened the riparian corridor, changed the channel from single thread to anastomosing, increased the water table height, and created numerous dams and ponds. Furthermore, the beaver-impacted section of river was maintained through both seasonal droughts and a significant flood event in winter 2021. We use a combination of field surveys, remotely-sensed vegetation indices, high-resolution satellite and aerial imagery, photospheres, and wildlife cameras to characterize the beaver-driven ecohydrologic and ecogeomorphic changes occurring at the site between June 2020 and September 2021. Our data suggests that beavers are capable of creating complex wetlands along the main stem of large rivers, and that these changes can occur on relatively short timescales.