MULTI-TEMPORAL SURFACE CHARACTERIZATION OF ACTIVE CHANNEL ROUGHNESS, GRAIN SIZE DISTRIBUTION, AND MORPHOLOGY USING SUB-MILLIMETER DIGITAL SURFACE MODELS GENERATED USING STRUCTURE FROM MOTION PHOTOGRAMMETRY

The spatial organization of an alluvial stream channel is the product of the interaction between the hydrologic flow regime and the sediment supply. Particle mobility is limited by critical shear stresses that are dependent on both particle size and discharge. Distinguishing between discharges that exhibit partial transport conditions for fine sediments is an important factor for biogeomorphic habitat classification in sediment impaired watersheds. This study describes a workflow for the rapid acquisition and automated analysis of topographic and spectral geospatial coverages of active channel cross sections using Structure From Motion Photogrammetry. Several historically surveyed cross sections have been reoccupied on the South Fork of the Eel River and two major tributaries in Northwest California. This process can rapidly produce arbitrarily high resolution, geographically registered spectral and topographic coverages of stream bed cross sections, appropriate for input and validation of hydrodynamic models. Particle size distribution has been determined using an image segmentation algorithm based on spectral distance and compactness. The application of change detection procedures can quantify the geomorphic effectiveness of the intervening flows between survey intervals for gauged watersheds.