Evaluating satellite-based depth mapping for large river monitoring: A case study of Peace River, British Columbia, Canada

Accurate and reliable methods to measure water depth are essential for informed river research and management. Remote sensing presents a powerful tool for efficient characterization of fluvial systems, but more research is needed into the applicability of bathymetric mapping in a range of conditions and environments. This study assessed the utility of mapping water depth from satellite imagery in a large, seasonally turbid river. Steps included analysis of relationships between image properties and water depth, assessment of the effects of image pre-processing, and comparison of two methods for calibrating image values to depths. It was determined that spectral depth mapping is applicable in the system, with a depth signal described by the ratio of green to red wavelengths. Pre-processing steps including the automated removal of shadows and water surface reflections and the application of a median filter improved the quality of depth calibrations, and calibration methods gave similar results with errors of 25% of reach average depth. The resulting depth maps reliably captured the overall hydromorphic forms and distribution of habitat features, although results were less reliable in deep areas (> 2 m) due to the saturation of the depth signal. Overall, satellite depth mapping can be an appropriate tool for repeat, broad-scale, long-term large river monitoring in general, and could potentially improve flood inundation models based primarily on subareal LiDAR surveys.