31 Aug 2023

Effects of Sedimentation on Three Hawaiian Coral Species under Laboratory Conditions

Abstract: Sedimentation can occur near a dredge operation in pulses over days, and potentially impact coral reefs occurring in close proximity. To improve the ability to predict the effects of dredging on corals, the effects of sedimentation in two 18-day experiments were studied for three common coral species representing different morphologies. In a laboratory setting, coral fragments were exposed to four sedimentation concentrations dosed every four days ranging from 0 to 60 mg cm-2. Separate experiments were performed in series, once with fine grain sediment and repeated with a coarse grain sediment. A 30-day sediment free observation period followed each experiment. Coral responses were measured throughout the experiment and at the end of the 18-day exposure and 30-day sediment free observation period. Photosynthetic yield, lipid ratios, tissue color, tissue loss, growth, and sediment cover varied among the treatment groups. All coral species were minimally affected when sediment concentrations were at or below 6 mg cm-2. P. meandrina and P. lobata experienced the most sediment coverage and tissue loss when exposed to sediment concentrations >30 mg cm-2 for either sediment. M. capitata experienced no sediment coverage or tissue loss when exposed to either sediment, but a reduction in photosynthetic yield at 60 mg cm-2 fine grain sediment was observed. During the 30-day post-exposure sediment free observation period, P. meandrina tissue loss continued, P. lobata nearly completely regrew lost tissue, while M. capitata showed no lingering effects. This study improves the US Army Corps of Engineers (USACE) ability to estimate the impacts of dredging on coral reefs.

29 Aug 2023

Unmanned Ground Vehicle (UGV) Full Coverage Planning with Negative Obstacles

Abstract: We explored approaches that offer full coverage path planning while simultaneously avoiding negative obstacles. These approaches are specific to unmanned ground vehicles (UGVs), which need to constantly interact with a traversable ground surface. We tested multiple potential solutions in simulation, and the results are presented herein. Full coverage path planner (FCPP) approaches were evaluated based on their ability to discretize their paths, use waypoints effectively, and be easily integrated with our current robot platform. For negative obstacles, we explored approaches that will integrate with our current navigation stack. The preferred solution will allow for teleoperation, waypoint navigation, and full autonomy while avoiding positive and negative obstacles

28 Aug 2023

Improving Spatial and Temporal Monitoring of Dredging Operations Incorporating Unmanned Technologies

Abstract: The US Army Corps of Engineers (USACE) is responsible for maintaining safe and navigable waterways through the periodic dredging of shoaled sediment from federal navigation channels. While dredging, a portion of the bottom sediments become resuspended creating a sediment plume near the dredging operation. Suspension of sediments during dredging and dredged sediment disposal operations continues to be a primary concern of regulatory agencies charged with the protection of environmental resources. Consequently, almost all dredging projects incorporate some level of regulatory compliance monitoring dedicated to measuring sediment resuspension. For numerous reasons the conventional approach using manned surface vessels to perform compliance monitoring is frequently ineffective in both adaptively managing dredging projects and ensuring true environmental protection. Advancements in unmanned platforms and payload technologies offer new and potentially more robust alternatives to conventional platforms. In this study, the use of unmanned aerial system (UAS) and weather balloon mounted camera imagery was demonstrated, and the use of an unmanned surface vessel (USV) to monitor turbidity in navigation channels and near a dredging operation. The imagery from the UAS and weather balloon were compared to in-situ turbidity measurements in a turbid distributary channel and near a dredging operation, while the USV was used to learn more about in-situ turbidity associated with passing vessels in a navigation channel. The results of the demonstrations show the unmanned technology bundled with off-the-shelf payloads can help to produce evidence-based information through easily interpreted aerial imagery and in situ measurements which can help to inform and manage water quality in areas where sediment plumes are an environmental concern.

28 Aug 2023

Scaling and Sensitivity Analysis of Machine Learning Regression on Periodic Functions

Abstract: In this report we document the scalability and sensitivity of machine learning (ML) regression on a periodic, highly oscillating, and 𝐶∞ function. This work is motivated by the need to use ML regression on periodic problems such as tidal propagation. In this work, TensorFlow is used to investigate the machine scalability of a periodic function from one to three dimensions. Wall clock times for each dimension were calculated for a range of layers, neurons, and learning rates to further investigate the sensitivity of the ML regression to these parameters. Lastly, the stochastic gradient descent and Adam optimizers wall clock timings and sensitivities were compared.

25 Aug 2023

Wildrice (Zizania palustris; Manoomin) Biology, Functions and Values, and Soil Physiochemical Properties Affecting Production: A Review of Available Literature

Abstract: Wildrice (Zizania palustris L.) is an annual aquatic emergent plant primarily distributed across portions of Minnesota, Wisconsin, Michigan, and Canada. Wildrice requires narrow environmental conditions that vary throughout its life cycle. Environmental conditions required include water levels between 15 and 90 cm, slow flowing water, anaerobic soil, and circum-neutral pH. Wildrice production and abundance is most often limited by nitrogen availability. Both short- and long-term changes in local conditions impact distribution and abundance of wildrice at local and regional scales. Reported declines in wildrice production have increased interest in evaluating changing environmental conditions, specifically within the Upper Peninsula of Michigan. Wildrice, or manoomin, is an important food and cultural resource, and remains important to native peoples throughout the region, including the Lac Vieux Desert Band of Lake Superior Chippewa Indians. This report provides a review of literature related to wildrice and examines potential factors affecting its production in the Upper Peninsula of Michigan. This report highlights cultural and traditional values, functions and values of wildrice, and unique chemical and physical aspects of the environment where wildrice grow. Additionally, this report synthesizes the data gathered in the literature review, identifies knowledge gaps, and provides research opportunities for improved wildrice production in the Great Lakes region.

24 Aug 2023

Houston Ship Channel Numerical Model Update and Validation

Abstract: The Houston Ship Channel (HSC) is one of the busiest deep-draft navigation channels in the United States and must be able to accommodate increasing vessel sizes. The US Army Corps of Engineers, Galveston District (SWG), requested the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, update and revalidate a previously developed three-dimensional Adaptive Hydraulics (AdH) hydrodynamic and sediment model of the HSC, Galveston, and Trinity Bays. The model is necessary for analyzing potential impacts on salinity, sediment, and hydrodynamics due to alternatives designed to reduce shoaling in the HSC. SWG requested an updated validation of the previously developed AdH model of this area to calendar years 2010 and 2017, utilizing newly collected sediment data. Updated model inputs were supplied for riverine suspended sediment loads as well as for the ocean tidal boundary condition. The updated model shows good agreement to field data in most conditions but also indicates potential issues with freshwater flow inputs as well as the ocean salinity boundary condition.

24 Aug 2023

3D Measurements of Water Surface Elevation Using a Flash Lidar Camera

Abstract: This Coastal and Hydraulics Engineering technical note (CHETN) presents preliminary results from a series of tests conducted at the US Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), Field Research Facility (FRF), in Duck, North Carolina, to explore the capabilities and limitations of the GSFL16K Flash Lidar Camera in nearshore science and engineering applications. The document summarizes the spatial coverage and density of data collected in three deployment scenarios and with a range of tuning parameters and provides guidance for future deployments and data-collection efforts.

24 Aug 2023

Measuring Maritime Connectivity to Puerto Rico and the Virgin Islands Using Automatic Identification System (AIS) Data

Abstract: The purpose of this Coastal and Hydraulics Engineering technical note (CHETN) is to summarize a portion of recently published work (Young, Kress, et al. 2022) that used archival Automatic Identification System (AIS) data to measure the commercial vessel traffic connected to Puerto Rican and US Virgin Island (USVI) port areas from January 2015 to June 2020. Vessel movement derived from AIS was aggregated to construct a network that measured the port-to-port connectivity for all ports in the network and the interconnectivity of traffic between those ports. AIS data provided a description of vessel movement and the identification of specific vessel classes. Metrics such as interconnectedness can be used in conjunction with standard US Army Corps of Engineers (USACE) metrics describing waterway utilization, which traditionally have included total tonnage and specific commodity tonnage. The ability to consider the self-selected vessel-type broadcast via AIS, as well as dominant commodity type and tonnage reported through statistical publications, provides a fuller and more accurate description of waterway capacity utilization. This knowledge, along with port-to-port interconnectedness, reveals potential redundancies between ports, robustness across supply chains, and the impacts of seasonality, thereby allowing the USACE to expand its understanding of maritime supply-chain resilience.

24 Aug 2023

Geomorphic Metrics Used in FluvialGeomorph

Abstract: FluvialGeomorph (FG) is a geographic information system-based geomorphic analysis toolkit that analyzes high-resolution terrain data to provide river-reach assessments for watershed studies. This report demonstrates the utility of FG to identify physical stream channel characteristics that are used to determine channel stability. The FG toolbox is a remote-sensing approach based on lidar data, designed to measure channel, floodplain, valley, and watershed metrics necessary for watershed assessments. Currently, channel slope and cross-sectional analysis and planform metrics are being evaluated with existing lidar data from different hydrophysiographic regions within the United States. Recent study areas include the Northwest, Southwest, South, Midwest, and upper Midwest of the United States.

18 Aug 2023

Unmanned Ground Vehicle (UGV) Path Planning in 2.5D and 3D

Abstract: Herein, we explored path planning in 2.5D and 3D for unmanned ground vehicle (UGV) applications. For real-time 2.5D navigation, we investigated generating 2.5D occupancy grids using either elevation or traversability to determine path costs. Compared to elevation, traversability, which used a layered approach generated from surface normals, was more robust for the tested environments. A layered approached was also used for 3D path planning. While it was possible to use the 3D approach in real time, the time required to generate 3D meshes meant that the only way to effectively path plan was to use a preexisting point cloud environment. As a result, we explored generating 3D meshes from a variety of sources, including handheld sensors, UGVs, UAVs, and aerial lidar.