Repeated terrestrial-laser-scanner surveys of riverbanks along the South River, VA

Abstract

In recent decades, the increased spatial resolution of commercially available terrestrial laser-scanners (TLS) has led to the widespread use of these instruments for monitoring changing physical conditions in a variety different fluvial systems. This proliferation of TLS surveys allowed researchers to observe processes at both spatial and temporal scales that otherwise would be difficult or impossible with traditional survey methods. Presented herein is one of the temporally longest known time-series of TLS riverbank surveys focused on changes in erosion and deposition. Channel wall topography was monitored over a 13-year period at 13 different sites along a 10-mile reach of the South River, Virginia as part of an interdisciplinary research project to determine rates of riverbank erosion and deposition of mercury-contaminated sediments. Difference models derived from the TLS data collected during three field seasons indicate that the topographic changes observed display significant spatial variability (i.e., small areas experience intense erosion over a just a few years). These unique, longitudinal observations increase our understanding of streamwise erosional trends and may be useful for informing models where such data is typically not available. In all the study locales, the foci of the most intense erosion observed between surveys of a few years smooths to create a more laterally homogeneous erosion profile when analyzed over a decadal scale. Interestingly, despite areas of short-term, intense erosion and deposition, our results suggest that, on a decade-scale, rates of sediment flux from riverbank difference models converge on those observed using photogrammetric techniques.