7 Jan 2025

Geomorphic Assessment of the St. Francis River Phase II

Abstract: Significant sedimentation issues persist within the St. Francis Basin as a result of extensive drainage alterations. The objective of this study is to characterize the bed and bank sediment throughout the study reach and identify potential sources of sediment contributing to the sanding issues below Holly Island. The sedimentation below Holly Island increases the Memphis District’s maintenance needs in the St. Francis River Basin by requiring millions of dollars for channel cleanout and bank stabilization projects. This effort synthesizes prior geomorphic studies and existing survey data to break the study reach into seven geomorphic reaches of interest. Simultaneously, 151 bed samples and 137 bank samples were collected to characterize the sediments within the study reach to develop a data dictionary for future sediment budget development. Results show the St. Francis River is a poorly sorted, sand-bed river overlain by 10 to 20 feet of silts and clays along the banks. Iron Bridge to Highway U (Reach 1-3) may reach pseudo-stability so long as existing grade-control structures and bank stabilization features remain. Reach 6, between St. Francis and Brown’s Ferry, is evolving with one cutoff forming and one cutoff recently complete. This reach may be a source of sediment to downstream reaches.

11 Dec 2024

Adaptive Hydraulics (AdH) Version 4.7.1 Sediment Transport User’s Manual: A 2D Modeling System Developed by the Coastal and Hydraulics Laboratory

Abstract: Guidelines are presented for using the US Army Corps of Engineers (USACE) Adaptive Hydraulics (AdH) modeling software to model 2D shallow water problems with sediment transport (i.e., AdH linked to the Sediment Transport Library [SEDLIB]). This manual describes the inputs necessary to use the SEDLIB sediment transport library from within AdH, to perform coupled hydrodynamic, sediment, and morphological computations. The SEDLIB sediment transport library is intended to be of general use and, as such, examples are given for basic sediment transport of cohesive, noncohesive, and mixed suspended sediment loads and bedload.

11 Dec 2024

Numerical Modeling of Supercritical Flow in the Los Angeles River: Part II: Existing Conditions Adaptive Hydraulics Numerical Model Study

Abstract: The Los Angeles District of the US Army Corps of Engineers is assisting the City of Los Angeles with restoration efforts on the Los Angeles River. The city wishes to restore portions of the channelized river to a more natural state with riparian green spaces for both wildlife and public recreation usage. The Los Angeles River provides an important role from a flood-control perspective, and functionality needs to be preserved when contemplating system modifications. This report details the development of an Adaptive Hydraulics numerical model capable of modeling this complex system consisting of both subcritical and supercritical flow regimes. The model geometry was developed to represent the existing conditions system for future usage in quantifying the impact associated with proposed restoration alternatives. Due to limited hydraulic data in the study area, an extensive model validation to observed data was not possible. A model was developed and simulated using the most appropriate input parameters. Given the lack of measured data for model validation, an extensive number of sensitivity simulations were completed to identify the most impactful parameters and quantify a reasonable level of confidence in the model results based on the uncertainty in the model inputs.

2 Dec 2024

Establishing a Workflow for Near-Seamless Digital Elevation Model Creation in the Great Lakes for ADCIRC Modeling

Abstract: This report introduces a workflow to create near-seamless, regional digital elevation models (DEMs) for use in coupled Advanced Circulation and Simulating Waves Nearshore modeling. The workflow is based in Esri ArcGIS Pro, leveraging the Mosaic Dataset architecture to organize and mosaic survey data sets into near-seamless DEMs. This workflow includes data collection and preprocessing, creation of source and derived mosaic data sets, manual editing of the data set seamlines, the creation of spatial metadata products, and quality assurance and control measures. These steps were implemented for each Great Lake to provide a high-resolution, near-seamless DEM product for modelers. The workflow may also have utility for other regional-scale investigations.

2 Dec 2024

Comparison of Run-Up Models with Field Data

Abstract: Run-up predictions are inherently uncertain, owing to ambiguities in phase-averaged models and inherent complexities of surf and swash-zone hydrodynamics. As a result, different approaches, ranging from simple algebraic expressions to computationally intensive phase-resolving models, have been used in attempt to capture the most relevant run-up processes. Studies quantifiably comparing these methods in terms of physical accuracy and computational speed are needed as new observation technologies and models become available. The current study tests the capability of the new swash formulation of the Coastal Modeling System (CMS) to predict 1D run-up statistics (R2%) collected during an energetic 3 week period on sandy dune-backed beach in Duck, North Carolina. The accuracy and speed of the debut CMS swash formulation is compared with one algebraic model and three other numerical models. Of the four tested numerical models, the CSHORE model computed the results fastest, and the CMS model results had the greatest accuracy. All four numerical models, including XBeach in surfbeat and nonhydrostatic modes, yielded half the error of the algebraic model tested. These findings present an encouraging advancement for phase-averaged coastal models, a critical step towards rapid prediction for near-time deterministic or long-term stochastic guidance.

2 Dec 2024

Adaptive Hydraulics 2D Shallow Water (AdH-SW2D) User’s Manual (Version 4.7.1): Guidelines for Solving 2D Shallow Water Problems with the Adaptive Hydraulics Modeling System

Abstract: Guidelines are presented for using the US Army Corps of Engineers Adaptive Hydraulics modeling software to model 2D shallow water problems. Constituent (nonsediment) transport is also included in this document. Sediment transport instructions are contained in a supplemental user’s guide.

5 Nov 2024

Improving Aquatic Placement Practices for Beneficial Use of Dredged Material in the Great Lakes

Abstract: The Great Lakes Navigation System is an economically critical waterway. To maintain safe and navigable waterways, approximately 3–5 million yd3 (2.3–3.8 million m3) of sediments are dredged annually. The US Army Corps of Engineers (USACE) and others now recognize that beneficial use of these sediments can achieve positive economic, environmental, and social outcomes. However, historically less than 25% of dredged sediments have been beneficially used in the nearshore environment. Improvements are needed in dredged material management practices in the Great Lakes to achieve the goal of using 70% of dredged sediments beneficially by 2030. Therefore, to overcome these challenges this report reviews beneficial use of dredged material projects with the goal of improving and in-creasing beneficial-use-placement practices in the Great Lakes. Identified needs to advance beneficial-use placement in the Great Lakes include the following: (1) improved modeling of sediment-placement methods; (2) better documentation regarding the cost, benefits, and drawbacks of various placement methods; (3) demonstration of some sediment-placement techniques used successfully in other coastal environments; and (4) monitoring before and after conditions, particularly for sediments that contain greater than 10% fines. Several demonstration projects should be implemented to obtain information addressing the data gaps.

9 Oct 2024

Performance of High-Resolution, Acoustic Mapping Systems in a Fluid-Mud Environment : Testing the Effectiveness and Viability of High-Resolution, Hydrographic Survey Systems in a Fluid-Mud Environment

Abstract: This study explores the use of high-resolution acoustic mapping systems to penetrate fluid-mud layers by quantitatively relating depth with operating frequency. Prior to this study, multibeam surveys have proven be an effective method to elucidate the seafloor and collect bathymetric data on various bodies of water including rivers, lakes, bays, and the oceans. These techniques are regularly used on US Army Corps of Engineers dredged and federally maintained navigation channels. The objective of the study was to test the effectiveness of commercial off-the-shelf, low-frequency, high-resolution acoustic survey systems to penetrate fluid mud and if so, determine the density at penetration. The testing method combined multibeam echosounder, sub-bottom profiler, and single-beam echo sounder. In addition, in situ testing was conducted to determine the density of fluid-mud layers using a RheoTune profiler and laboratory testing. Results indicate that the use of currently available, bathymetric mapping systems operating at 90 kHz and higher are incapable of penetrating fluid mud in riverine and coastal shallow water conditions. This study demonstrates that while multibeam technology is effective at penetrating the water column, current frequencies available on the market are unable to penetrate fluid-mud layers in a riverine and shallow-water environment.

3 Oct 2024

Comite Diversion Numerical Model Study

Abstract: The Comite River diversion project is designed to reduce flooding along the Comite and Amite Rivers during flood events by diverting flow from the Comite River into the Mississippi River above Baton Rouge, Louisiana. The flow is diverted from the Comite River along a diversion canal to the Lilly Bayou Control structure. This structure allows the Comite River flow to enter the Mississippi River floodplain. A numerical model was created to evaluate the impacts associated with this addition of water to the Mississippi River. A 2D Adaptive Hydraulics numerical model was created to quantify the system impacts associated with the diverted flow in conjunction with possible system modifications to control the flow pathway. The impact of the diversion was determined to be heavily dependent on the flow and stage of the Mississippi River. At higher stages and flows, the flow diverted by the Lilly Bayou Control structure is negligible in relation to the much larger Mississippi River flow and therefore the impacts of the added flow are significantly less than at lower Mississippi River stages. At lower Mississippi River flows and stages, the added flow from the Lilly Bayou Control structure has a larger impact on the inundation due to the larger relative amount of diverted flow in relation to the Mississippi River. Ultimately, the diverted Comite River flow has some incremental increase in water levels at all Mississippi River stages.

27 Sep 2024

Potential Engineering With Nature Features to be Incorporated at Woodtick Peninsula

Purpose: Woodtick Peninsula is a barrier peninsula in western Lake Erie where restoration activities are being planned to combat erosion of the peninsula wetlands through placement of dredged material. As part of the restoration effort, design of an artificial reef is currently underway to function as a breakwater, preventing erosion of the fine-grained material being hydraulically placed along the west side of the peninsula. To the extent possible, it is desirable to design the reef such that it would not only provide erosion protection, but also incorporate features that would provide habitat, and thereby support the goals of Engineering With Nature® (EWN®). EWN is a concept focused on aligning natural and engineering processes to deliver economic, environmental, and social benefits efficiently and sustainably through collaboration. A range of breakwater and shoreline armoring alternatives have been utilized in coastal environments to enhance habitat. While a number of alternatives have been successfully demonstrated in marine waters, fewer structures have been adapted to freshwater systems of the Great Lakes. However, there have been several demonstrations within the Great Lakes in which breakwater structures have been enhanced to incorporate habitat features. In this report, potential designs for breakwaters and shoreline edging in freshwater systems that can incorporate EWN benefits are summarized.