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A low-cost multicamera Unmanned Aircraft System (UAS) is used to simultaneously estimate open-coast topography and bathymetry from a single longitudinal coastal flight. The UAS combines nadir and oblique imagery to create a wide field of view (FOV), which enables collection of mobile, long dwell timeseries of the littoral zone suitable for structure-frommotion (SfM), and wave speed inversion algorithms. Resultant digital surface models (DSMs) compare well with terrestrial topographic lidar and bathymetric survey data at Duck, NC, USA, with roor-mean-square error (RMSE)/bias of 0.26/-0.05 and 0.34/-0.05 m, respectively. Bathymetric data from another flight at Virginia Beach, VA, USA, demonstrates successful comparison (RMSE/bias of 0.17/0.06 m) in a secondary environment. UAS-derived engineering data products, total volume profiles and shoreline position, were congruent with those calculated from traditional topo-bathymetric surveys at Duck. Capturing both topography and bathymetry within a single flight, the presented multicamera system is more efficient than data acquisition with a single camera UAS; this advantage grows for longer stretches of coastline (10 km). Efficiency increases further with an on-board Global Navigation Satellite System-Inertial Navigation System (GNSS-INS) to eliminate ground control point (GCP) placement. The Appendix reprocesses the Virginia Beach flight with the GNSS-INS input and no GCPs. The resultant DSM products are comparable [root-mean-squared difference (RMSD)/bias of 0.62/−0.09 m, and processing time is significantly reduced.

The 2017 Duck Unmanned Aircraft Systems (UAS) Pilot Experiment was designed to evaluate existing and new UAS-based survey and monitoring techniques beneficial to U.S. Army Corps of Engineers Flood Risk Management (FRM). The diverse array of UAS sensors (lidar, multispectral packages, and high-resolution cameras) can collect data to estimate topography, bathymetry, terrain, land cover, vegetation, and structures at high temporal and spatial resolution. The experiment took place on 5-24 June 2017 at the U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Field Research Facility. Nine UAS flight teams from the federal government, academia, and the private sector conducted 180 UAS flights with 10 different UAS platforms as well as 2 traditional fixed-wing plane overhead surveys. The UAS flights combined for over 2,782 minutes of air time across estuarine, dune, beach, and nearshore environments, including various types of natural features and man-made infrastructure. Such datasets provide the foundation for quantitatively comparing the pros and cons of different platforms, sensor packages, and processing techniques against each other as well as traditional survey methods. This special report summarizes the cooperative June 2017 UAS for FRM pilot field experiment; sections detail participating groups, airframes, field preparation/field operations, and data dissemination. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

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The presented study reports on numerical simulations of flows in tidal channels near Rose Dhu Island, GA, which is used to identify hotspots of hydrokinetic energy and to assess the tidal stream energy potential at this site. The numerical simulations are complemented with field measurements of local current velocities and water surface heights, which are used to validate the simulations. Both velocity distributions and water surface heights as predicted by the numerical model are in good agreement with observed data. The simulations reveal a tidal asymmetry in the encompassing Ogeechee estuary with the ebb tide currents dominating over the flood tide ones. The model is able to successfully predict the distribution of discharge into the smaller creeks around Rose Dhu Island and thereby capturing the location of local hotspots of hydrokinetic energy. It is found that local hotspots do exist near the island, and the analysis suggests the maximum available annual power of 4.75 MW, with a peak estimated extraction surpassing 4 KW during Spring tides.

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