| This aim of this study is to understand the coupled relationship between rivers and their surrounding hillslopes during and following base level fall. To do this we examine (1) the placement and longitudinal age variation of strath terraces and (2) the form, frequency and position of mass movements below, at and above a mainstem knickpoint. Our findings from the South Fork Eel River, in northern California indicate that incision initiated ~ 134,000 years ago and was accomplished through progressive upstream knickpoint retreat, as alluvial sediments on terrace treads show two clusters of ages which young upstream. Hillslopes responded to base level fall in a similar progressive manner, as the frequency of mass movements decrease in with distance upstream, with mass movements having a larger impact on the adjusted lower basin of the South Fork Eel River, than the relict upper basin. Translational slides dominate throughout the basin, with a decrease in the number of earth flows present with distance upstream, and an increase in the number of debris flows with distance to the knickzone.
Keywords:
Geomorphology, landscape evolution, landslides, fluvial terraces, OSL dating, hillslope-channel coupling, strath terrace, Northern California, transience, South Fork Eel River, LiDAR, bulk OSL sampling, landslide mapping |