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  • Simulations of Shoreline Changes along the Delaware Coast

    Abstract: This technical report presents two applications of the GenCade model to simulate long-term shoreline evolution along the Delaware Coast driven by waves, inlet sediment transport, and longshore sediment transport. The simulations also include coastal protection practices such as periodic beach fills, post-storm nourishment, and sand bypassing. Two site-specific GenCade models were developed: one is for the coasts adjacent to the Indian River Inlet (IRI) and another is for Fenwick Island. In the first model, the sediment exchanges among the shoals and bars of the inlet were simulated by the Inlet Reservoir Model (IRM) in the GenCade. An inlet sediment transfer factor (γ) was derived from the IRM to quantify the capability of inlet sediment bypassing, measured by a rate of longshore sediments transferred across an inlet from the updrift side to the downdrift side. The second model for the Fenwick Island coast was validated by simulating an 11-year-long shoreline evolution driven by longshore sediment transport and periodic beach fills. Validation of the two models was achieved through evaluating statistical errors of simulations. The effects of the sand bypassing operation across the IRI and the beach fills in Fenwick Island were examined by comparing simulation results with and without those protection practices. Results of the study will benefit planning and management of coastal sediments at the sites.

  • Evaluation of Unmanned Aircraft System Coastal Data Collection and Horizontal Accuracy: A Case Study at Garden City Beach, South Carolina

    Abstract: The US Army Corps of Engineers (USACE) aims to evaluate unmanned aircraft system (UAS) technology to support flood risk management applications, examining data collection and processing methods and exploring potential for coastal capabilities. Foundational evaluation of the technology is critical for understanding data application and determining best practices for data collection and processing. This study demonstrated UAS Multispectral (MS) and Red Green Blue (RGB) image efficacy for coastal monitoring using Garden City Beach, South Carolina, as a case study. Relative impacts to horizontal accuracy were evaluated under varying field scenarios (flying altitude, viewing angle, and use of onboard Real-Time Kinematic–Global Positioning System), level of commercial off-the-shelf software processing precision (default optimal versus high or low levels) and processing time, and number of ground control points applied during postprocessing (default number versus additional points). Many data sets met the minimum horizontal accuracy requirements designated by USACE Engineering Manual 2015. Data collection and processing methods highlight procedures resulting in high resolution UAS MS and RGB imagery that meets a variety of USACE project monitoring needs for site plans, beach renourishment and hurricane protection projects, project conditions, planning and feasibility studies, floodplain mapping, water quality analysis, flood control studies, emergency management, and ecosystem restoration.

  • Framework Geology of Cape Shoalwater and Northwest Willapa Bay, Washington: Assessing Potential Geologic Impacts on Recent Shoreline Change

    Abstract: The shoreline along Cape Shoalwater and northwest Willapa Bay has experienced the highest rates of erosion along the entire Pacific Coast of the United States, due in part to rapid northward migration of the navigation channel. Recently, channel migration and shoreline erosion in this region have slowed, but the cause of this relative stabilization, and thus the longevity of these new patterns, is unknown. Given the complex neotectonics and geologic framework of the southern coast of Washington, it is possible that underlying, erosion-resistant geologic units have become exposed along the channel and/or in the nearshore, and are acting to reduce or halt channel migration and/or shoreline erosion. Conversely, the apparent reduction may be due to subtle, short-term changes in regional hydrodynamics and/or sediment transport, and thus future rates of channel migration and/or shoreline erosion might increase back to historical rates. The purpose of this special report is to detail the geologic and neotectonic framework of the northern Willapa Bay region, and determine how the underlying framework geology might be impacting channel stability and adjacent shoreline erosion rates. Suggested research questions to quantify potential geologic control are also presented, including the potential benefits of the research to the district.

  • PUBLICATION NOTICE: Computer-Based Calibration and Uncertainty Analysis of GenCade: Description and Proof of Concept

    Purpose: This Coastal and Hydraulics Engineering Technical Note (CHETN) provides a description of a methodology for the computer-based calibration or Parameter Estimation (PE) and corresponding Uncertainty Analysis (UA) for the shoreline change model GenCade developed by the US Army Corps of Engineers. This work demonstrates the suitability and benefits of applying the proposed PE and UA methods to GenCade studies using an idealized case as well as a simple field study as a proof of concept. This document is primarily for engineers and decision-makers interested in the implementation of PE and UA in one-line shoreline change models such as GenCade.

  • PUBLICATION NOTICE: Sediment Sorting by Hopper Dredging and Pump-Out Operations: Conceptual Model and Literature Review

    Abstract: Dredged sediment placed on beaches or nearshore environments is customarily evaluated for compatibility with the native beach sediment to avoid unintended impacts to economic, environmental, or recreational resources. Consequently, some state regulatory authorities establish limits upon the fine-grained content for sediment designated for placement on certain beaches and nearshore environments. Hopper dredging operations for beach and nearshore placement typically include periods of overflow, which is recognized to produce some degree of separation between the size fractions of the dredged sediment. The degree of separation and the controlling factors of separation are presently poorly known and are the subject of this research. This report provides a conceptual model of the hopper dredging and placement processes, including the relevant processes associated with hopper dredge-associated sediment dynamics, generation and transport of the overflow sediment plume, and sediment winnowing at the beach outflow. Prior research is described, and knowledge gaps are identified. Finally, a research plan to validate prior research and to address knowledge gaps is presented. An annotated bibliography of relevant literature is given in an appendix. Documentation of the planned research presented herein will appear in future publications associated with this study.

  • PUBLICATION NOTICE: Nearshore Placement Workshop 2019: Sediment Nourishment of the Nearshore Environment

    Abstract: The Coastal Inlets Research Program and the Regional Sediment Management Program co-sponsored the 2019 Nearshore Placement Workshop. Thirty-four participants from the US Army Engineer Research and Development Center (ERDC) and numerous districts met in Vicksburg on January 29–30, 2019, as a part of the workshop. This workshop was convened to facilitate discussions on concerns districts face regarding nearshore placements from resource agencies and stakeholders, challenges to placing sediment in the nearshore, and future research needs. The workshop included ERDC presentations on the state of the science regarding nearshore placements; specific implementations of nearshore placements within various US Army Corps of Engineers districts; break-out-style discussions on nearshore placement challenges and potential paths forward; and group discussions on metrics for success, quantification of benefits, Statements of Need (SON), and research priorities. A few of the major recurring themes throughout the workshop were the importance of monitoring, concerns over the fate of fine-grained sediment, and difficulties conveying the benefits of nearshore placements to a wide range of audiences. The workshop culminated in a discussion of possible SON to be put forth to the ERDC research and development community. This special report describes the discussions and outcomes of the 2019 Nearshore Placement Workshop.

  • PUBLICATION NOTICE: A Comparison of GenCade,  Pelnard-Considere, and LITPACK

    PURPOSE: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to investigate the basic physics and numerical code of GenCade by running a series of simplified test cases and comparing the results to another numerical shoreline evolution model and an analytical solution. The complementary numerical code is the widely used shoreline evolution model LITPACK. The analytical model is the original solution derived by Pelnard-Considere (1956). The underlying assumption in all three approaches is a beach profile of constant shape so that shoreline change is driven by long-shore transport processes and a combination of independent sediment sources or sinks (e.g., sea level change, subsidence). The CHETN presents a descriptive overview of the theory behind the models followed by an inter-comparison using a set of four test cases involving shoreline change in the vicinity of idealized coastal structures and a beach nourishment. GenCade shows good agreement with LITPACK, and both models compare well to the analytical solution for these idealized cases. The GenCade results indicate that the underlying numerical code and basic physical process are consistent with other widely used shoreline modeling systems.

  • PUBLICATION NOTICE: Cross-Shore Transport Feature for GenCade

    PURPOSE: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to introduce a new cross-shore transport capability in GenCade. The cross-shore transport feature is based on a new empirical algorithm that includes wave velocity skewness to calculate the near-bed sediment flux. Validation of the new algorithm was achieved using shoreline position data collected at the US Army Corps of Engineers (USACE) Field Research Facility (FRF) located in Duck, NC. This CHETN presents the theory behind the new cross-shore transport feature and validation using data collected at the FRF. Comparisons with and without the cross-shore feature are presented to demonstrate the improved GenCade performance. The CHETN concludes information that should be considered when using this new feature.

  • PUBLICATION NOTICE: Analysis of Nearshore Placement of Sediments at Ogden Dunes, Indiana

    ABSTRACT: The harbor structures/shoreline armoring on the southern Lake Michigan shoreline interrupt sand migration. Ogden Dunes, Indiana, and the nearby Indiana Dunes National Lakeshore observed shoreline erosion due to engineered structures associated with Burns Waterway Harbor (east of Ogden Dunes) impeding natural east-to-west sediment migration. To remedy this, USACE placed over 450,000 cubic meters (m3) of dredged material post-2006 in the nearshore of Ogden Dunes. However, the effectiveness of nearshore placements for shoreline protection and littoral nourishment is not fully established. To improve nearshore placement effectiveness, USACE monitored the June/July 2016 placement and subsequent movement of 107,000 m3 of dredged material in the nearshore region at Ogden Dunes. This involved an extensive monitoring scheme (three bathymetry surveys, and two acoustic Doppler current profiler deployments), a Coastal Modeling System (CMS) numerical model of the changes following placement, and a prediction of sediment transport direction using the Sediment Mobility Tool (SMT). The SMT-predicted sediment migration direction was compared to observations. Observations indicated that between 10/11/2016 and 11/15/2016 the centroid of the sediment above the pre-placement survey moved 17 m onshore. These observations agreed with SMT predictions — onshore migration under storm and typical wave conditions. CMS accurately reproduced the hydrodynamic features.

  • Army Corps seeks volunteers to restore America’s public lands

    The U.S. Army Corps of Engineers will host National Public Lands Day events at various lakes throughout the Pittsburgh District.