Riverbed response to high flows with installed willow spiling using Multiquadric Radial Basis Function (RBFMQ)

Abstract

To establish the success of any river engineering revetment, post-project monitoring is a critical part of the process. Vegetation structures often lack detailed biological or geomorphological data to aid management procedures and project planning. Apart from the survival and growth rates, data mapping detailed changes on the riverbed and its response to bankfull events are critical. Riverbed adjacent to two willow spilling structures on the River Stour in East Anglia, UK, was surveyed before and after high flow events. The random field data were gridded using Radial Basis Function with Multiquadric option (RBF MQ) to reconstruct the surface most accurately, as it was found to be the most effective out of three methods tested. Data were gridded, sliced and cross-sections were plotted and compared at each site before and soon after high flow events. Image maps were generated, and volumetric changes were calculated. At both sites, erosion dominated in the upstream and sedimentation in the downstream sections of the bed surveyed. Structure undercutting occurred at gravel site up to 29 cm which is a rate that needs a management intervention to prevent project failure.