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  • A Review of Tidal Embayment Shoaling Mechanisms in the Context of Future Wetland Placement

    Abstract: Wetland construction in tidally influenced embayments is a strategy for beneficial use of sediment dredged from nearby navigation channels. These projects have the potential to alter basin morphology, tidal hydrodynamics, and shoaling trends. This special report provides a broad review of the literature related to engineering-induced changes in tidal range, salinity, tidal prism, tidal asymmetry, and other known causes of shoaling. Each potential shoaling mechanism is then evaluated in the context of wetland placement to provide a foundation for future beneficial use research. Based on a compilation of worldwide examples, wetland placement may reduce tidal amplitude and enhance ebb current dominance, thus reducing shoaling rates in the channels. However, constructed wetlands could also reduce the embayment’s tidal prism and cause accelerated shoaling relative to the pre-engineered rate. Because constructed wetlands are often created in conjunction with navigation channel dredging, the system’s morphologic response to wetland construction is likely to be superimposed upon its response to channel deepening, and the net effect may vary depending on a variety of system- specific parameters. Planning for future wetland placements should include an evaluation of local hydrodynamic behavior considering these factors to predict site-specific response.
  • Ship-Induced Waves at Tybee Island, Georgia

    Abstract: Commercial vessels transiting the Savannah entrance channel intermittently generate large wake events at Tybee Island, Georgia, creating a potential hazard for beachgoers. However, not all commercial vessels generate large wakes, and the relationship between vessel dimensions, operating conditions, wake height, and drawdown magnitude is unclear. This study evaluates bathymetric data, high-frequency wave and vessel wake measurements, and broadcast vessel identification over a 4-month period with the goal of providing a quantitative characterization of vessel wake conditions at Tybee Island. Data from 1,386 cargo vessel passages and 202 tanker passages indicate that vessel dimensions (length and beam) are positively correlated with drawdown magnitude and secondary wake height, although large vessels do not consistently generate large wakes. Container ships, which tended to travel faster than tankers, corresponded to the largest wakes in the dataset. A further hypothesis is that tidally modulated energy dissipation may favor smaller vessel wake uprush at low tide and larger uprush at high tide, but this idea cannot be confirmed without additional measurements to quantify nonlinear wave propagation on the beach face. Based on the collected data, the study concludes with four recommendations for reducing risk to beachgoers.
  • Automation of Gridded HEC-HMS Model Development Using Python: Initial Condition Testing and Calibration Applications

    Abstract: The US Army Corps of Engineers’s (USACE) Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) rainfall-runoff model is widely used within the research community to develop both event-based and continuous rainfall-runoff models. The soil moisture accounting (SMA) algorithm is commonly used for long-term simulations. Depending on the final model setup, 12 to 18 parameters are needed to characterize the modeled watershed’s canopy, surface, soil, and routing processes, all of which are potential calibration parameters. HEC-HMS includes optimization tools to facilitate model calibration, but only initial conditions (ICs) can be calibrated when using the gridded SMA algorithm. Calibrating a continuous SMA HEC-HMS model is an iterative process that can require hundreds of simulations, a time intensive process requiring automation. HEC-HMS is written in Java and is predominantly run through a graphical user interface (GUI). As such, conducting a long-term gridded SMA calibration is infeasible using the GUI. USACE Construction Engineering Research Laboratory (CERL) has written a workflow that utilizes the existing Jython application programming interface (API) to batch run HEC-HMS simulations with Python. The workflow allows for gridded SMA HEC-HMS model sensitivity and calibration analyses to be conducted in a timely manner.
  • Risk-Based Prioritization of Operational Condition Assessments: Methodology and Case Study Results

    Abstract: USACE operates, maintains, and manages more than $232 billion of the Nation’s water resource infrastructure. USACE uses the Operational Condition Assessment (OCA) to allocate limited resources to assess condition of this infrastructure in efforts to minimize risks associated with performance degradation. The analysis of risk associated with flood risk management (FRM) assets includes consideration of how each asset contributes to its associated FRM watershed system, understanding the consequences of the asset’s performance degradation, and a determination of the likelihood that the asset will perform as expected given the current OCA condition ratings of critical components. This research demonstrates a proof-of-concept application of a scalable methodology to model the probability of a dam performing as expected given the state of its gates and their components. The team combines this likelihood of degradation with consequences generated by the application of designed simulation experiments with hydrological models to develop a risk measure. The resulting risk scores serve as an input for a mixed-integer optimization program that outputs the optimal set of components to conduct OCAs on to minimize risk in the watershed. This report documents the results of the application of this methodology to two case studies.
  • Numerical Analysis of Dike Effects on the Mississippi River Using a Two-Dimensional Adaptive Hydraulics Model (AdH)

    Abstract: This report describes the hydraulic effects of dikes on water surface elevation (WSE) and velocities in the Mississippi River near Vicksburg, MS, from Interstate 20 to Highway 80 using a previously calibrated 2D Adaptive Hydraulics numerical model. Dike heights and their associated hydraulic roughness values were varied to quantify the overall effects of adjustments to dike fields. Steady flows characterized as low, medium, and high conditions were simulated. The WSE and velocity difference plots were generated to illustrate the hydraulic effects on the river under all scenarios discussed above. Overall, the dike adjustments had negligible impacts on WSEs and showed minimal effects on velocities on a system wide scale.
  • National Ordinary High Water Mark Field Delineation Manual for Rivers and Streams : Interim Version

    Abstract: The ordinary high water mark (OHWM) defines the lateral extent of nontidal aquatic features in the absence of adjacent wetlands in the United States. The federal regulatory definition of the OHWM, 33 CFR 328.3(c)(7), states the OHWM is “that line on the shore established by the fluctuations of water and indicated by physical characteristics such as [a] clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas.” This is the first manual to present a methodology for nationwide identification and delineation of the OHWM. A two-page data sheet and field procedure outline a weight-of-evidence (WoE) methodology to organize and evaluate observations at stream sites. This manual presents a consistent, science-based method for delineating the OHWM in streams. It also describes regional differences and challenges in identifying the OHWM at sites disturbed by human-induced or natural changes and illustrates how to use remote data to structure field inquiries and interpret field evidence using the principles of fluvial science. The manual demonstrates that, in many landscape settings, the OHWM may be located near the bankfull elevation.
  • The DEM Breakline and Differencing Analysis Tool—Step-by-Step Workflows and Procedures for Effective Gridded DEM Analysis

    Abstract: The DEM Breakline and Differencing Analysis Tool is the result of a multi-year research effort in the analysis of digital elevation models (DEMs) and the extraction of features associated with breaklines identified on the DEM by numerical analysis. Developed in the ENVI/IDL image processing application, the tool is designed to serve as an aid to research in the investigation of DEMs by taking advantage of local variation in the height. A set of specific workflow exercises is described as applied to a diverse set of four sample DEMs. These workflows instruct the user in applying the tool to extract and analyze features associated with terrain, vegetative canopy, and built structures. Optimal processing parameter choices, subject to user modification, are provided along with sufficient explanation to train the user in elevation model analysis through the creation of customized output overlays.
  • Cross Country Mobility (CCM) Modeling Using Triangulated Irregular Networks (TIN)

    Abstract: Cross country mobility (CCM) models terrain that has insufficient or unavailable infrastructure for crossing. This historically has been done with either hand-drawn and estimated maps or with raster-based terrain analysis, both of which have their own strengths and weaknesses. In this report the authors explore the possibility of using triangulated irregular networks (TINs) as a means of representing terrain characteristics used in CCM and discuss the possibilities of using such networks for routing capabilities in lieu of a traditional road-based network. The factors used to calculate CCM are modified from previous methods to capture a more accurate measurement of terrain characteristics. Using a TIN to store and represent CCM information achieves comparable results to raster cost analysis with the additional benefits of an integrated network useful for visualization and routing and a reduction in the number of related files. Additionally, TINs can in some cases more accurately show the contours of the landscape and reveal feature details or impediments that may be lost within a raster, thus improving the quality of CCM overlays.
  • Understanding Plant Volatiles for Environmental Awareness: Chemical Composition in Response to Natural Light Cycles and Wounding

    Abstract: Plants emit a bouquet of volatile organic compounds (VOCs) in response to both biotic and abiotic stresses and, simultaneously, eavesdrop on emitted signals to activate direct and indirect defenses. By gaining even a slight insight into the semantics of interplant communications, a unique awareness of the operational environment may be obtainable (e.g., knowledge of a disturbance within). In this effort, we used five species of plants, Arabidopsis thaliana, Panicum virgatum, Festuca rubra, Tradescantia zebrina, and Achillea millefolium, to produce and query VOCs emitted in response to mechanical wounding and light cycles. These plants provide a basis for further investigation in this communication system as they span model organisms, common house plants, and Arctic plants. The VOC composition was complex; our parameter filtering often enabled us to reduce the noise to fewer than 50 compounds emitted over minutes to hours in a day. We were able to detect and measure the plant response through two analytical methods. This report documents the methods used, the data collected, and the analyses performed on the VOCs to determine if they can be used to increase environmental awareness of the battlespace.
  • Meteorological Influences of a Major Dust Storm in Southwest Asia during July–August 2018

    Abstract: Dust storms can be hazardous for aviation, military activities, and respiratory health and can occur on a wide variety of spatiotemporal scales with little to no warning. To properly forecast these storms, a comprehensive understanding of the meteorological dynamics that control their evolution is a prerequisite. To that end, we chose a major dust storm that occurred in Southwest Asia during July–August 2018 and conducted an observation-based analysis of the meteorological conditions that influenced the storm’s evolution. We found that the main impetus behind the dust storm was a large-scale meteorological system (i.e., a cyclone) that affected Southwest Asia. It seems that cascading effects from this system produced a smaller, near-surface warm anomaly in Mesopotamia that may have triggered the dust storm, guided its trajectory over the Arabian Peninsula, and potentially catalyzed the development of a small low-pressure system over the southeastern end of the peninsula. This low-pressure system may have contributed to some convective activity over the same region. This type of analysis may provide important information about large-scale meteorological forcings for not only this particular dust storm but also for future dust storms in Southwest Asia and other regions of the world.