Monitoring Coastal Geomorphic Change and Sediment Transport Using Kite Aerial Photography (KAP) and Structure-from-Motion (SfM) Photogrammetry

Abstract

Coastal areas are particularly suitable study sites for kite aerial photography (KAP) surveys because of consistent wind and open space. This study uses KAP surveys conducted in January, March, June, August, and October 2025, combined with Structure from Motion photogrammetry and spatially variable error modeling for DEM of Difference (DoD) thresholding to monitor a dune revegetation project at Ocean Beach in San Francisco. Two independent ground surveys were conducted in June and October to compare measured elevation data with KAP-derived elevation. A fuzzy inference system was used to model spatially variable error for uncertainty thresholding with a 95% confidence interval based on point cloud density and surface roughness. The elevation models (raw and thresholded) were then analyzed through geomorphic change detection to assess volumetric change over time. DoD estimates from the four sampling periods between flights were used to derive mass transport rates (120.09, 415.04, 270.86, and 102.22 kg m−1 d−1, respectively) from cross-sections aligned with estimated wind directions, with results similar to wind model estimates from the same time periods, ranging from 50 to 80% (R2 = 0.98) of the latter. This method holds promise for better connecting geomorphic to atmospheric research methods, especially important when pursuing process-based restoration.