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Coastal foredunes are topographically high features that can reduce vulnerability to storm-related flooding hazards. While the dominant aeolian, hydrodynamic, and ecological processes leading to dune growth and erosion are fairly well-understood, predictive capabilities of spatial variations in dune evolution on management and engineering timescales (days to years) remain relatively poor. In this work, monthly high-resolution terrestrial lidar scans were used to quantify topographic and vegetation changes over a 2.5 year period along a micro-tidal intermediate beach and dune. Three-dimensional topographic changes to the coastal landscape were used to investigate the relative importance of environmental, ecological, and morphological factors in controlling spatial and temporal variability in foredune growth patterns at two 50 m alongshore stretches of coast. Despite being separated by only 700 m in the alongshore, the two sites evolved differently over the study period. The northern dune retreated landward and lost volume, whereas the southern dune prograded and vertically accreted. At the start of and throughout the study, the erosive site had steeper foredune faces with less overall vegetation coverage, and dune growth varied spatially and temporally within the site. Deposition occurred mainly at or behind the vegetated dune crest and primarily during periods with strong, oblique winds (>∼45 ∘ from shore normal). Minimal deposition was observed on the mostly bare-sand dune face, except where patchy vegetation was present. In contrast, the response of the accretive site was more spatially uniform, with growth focused on the heavily vegetated foredune face. The largest differences in dune response between the two sections of dunes occurred during the fall storm season, when each of the systems’ geomorphic and ecological properties modulated dune growth patterns. These findings highlight the complex eco-morphodynamic feedback controlling dune dynamics across a range of spatial scales.

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.

The purpose of this Coastal and Hydraulics Engineering technical report is to present how elevation data is collected along the coast using terrestrial lidar scanners coupled with a global position system/inertial navigation system and assess the accuracy of the data. A brief overview of the technology utilized on the vehicle platform is presented, along with upcoming improvements. This is followed by a description of the data processing techniques utilized to create three-dimensional point clouds. Subsequent to that is a presentation of an accuracy assessment to provide an overall system performance summary and provide a few examples of data products and their uses. The accuracy assessment of the system resulted in a mean horizontal error of 0.075 meter (m), mean vertical error of 0.099 m, mean total error of 0.129 m, and an average repeatability of 0.05 m. The results of this report suggest that assigning a single accuracy value to a mobile lidar survey may misrepresent some of the spatially variable error throughout the survey, and further work should incorporate full error propagation to each point.

No abstract

Coastal dunes provide essential protection for infrastructure in developed regions, acting as the first line of defence against ocean‐side flooding. Quantifying dune erosion, growth and recovery from storms is critical from management, resiliency and engineering with nature perspectives. This study utilizes 22 months of high‐resolution terrestrial LiDAR (Riegl VZ‐2000) observations to investigate the impact of management, anthropogenic modifications and four named storms on dune morphological evolution along ~100 m of an open‐coast, recently nourished beach in Nags Head, NC. The influences of specific management strategies – such as fencing and plantings – were evaluated by comparing these to the morphologic response at an unmanaged control site at the USACE Field Research Facility (FRF) in Duck, NC (33 km to the north), which experienced similar environmental forcings. Various beach‐dune morphological parameters were extracted (e.g. backshore‐dune volume) and compared with aeolian and hydrodynamic forcing metrics between each survey interval. The results show that LiDAR is a useful tool for quantifying complex dune evolution over fine spatial and temporal scales. Under similar forcings, the managed dune grew 1.7 times faster than the unmanaged dune, due to a larger sediment supply and enhanced capture through fencing, plantings and walkovers. These factors at the managed site contributed to the welding of the incipient dune to the primary foredune over a short period of less than a year, which has been observed to take up to decades in natural systems. Storm events caused alongshore variable dune erosion primarily to the incipient dune, yet also caused significant accretion, particularly along the crest at the managed site, resulting in net dune growth. Traditional empirical Bagnold equations correlated with observed trends of backshore‐dune growth but overpredicted magnitudes. This is likely because these formulations do not encompass supply‐limiting factors and erosional processes. © 2019 John Wiley & Sons, Ltd.

Coastal Lidar and Radar Imaging System between 2011 and 2017 along the northern Outer Banks of North Carolina near the CHL Field Research Facility. The report briefly describes the system and study site as well as the survey data extents, collection dates, and environmental context and data access information for the point cloud and digital elevation model products. Initial morphology data products and initial analyses are presented including calculations of shoreline change, dune volume, beach volume, beach slope, and cumulative elevation change over the 6-year study period. Follow-on reports will update the description of the available data repository moving forward. 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.