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.

11 Sep 2024

Evaluating Topographic Reconstruction Accuracy of Planet Lab’s Stereo Satellite Imagery

Abstract: The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to document initial results to derive topography on the beachface in the northern Outer Banks, North Carolina, utilizing Planet Labs’ SkySat stereo panchromatic imagery processed in Agisoft Metashape. This technical note will provide an initial evaluation into whether Planet Lab’s SkySat imagery is a suitable image source for satellite Structure from Motion (SfM) algorithms as well as whether these data should be explored as a federal beach project monitoring tool. Depending on required accuracy, these data have the potential to aid coastal scientists, managers, and US Army Corps of Engineers (USACE) engineers in understanding the now-state of their coastlines and employ cost-effective adaptive management techniques.

6 Aug 2024

Tools and Technical Guidelines for Delineating the Extent of Tidal Waters: Proof of Concept

Abstract: The delineation of shorelines in tidally influenced waters, as well as the inland extent of tidal influence of those waters, is often used to define the extent of federal and/or state jurisdictional boundaries, including the US Army Corps of Engineers’ (USACE) limits of jurisdiction under the Rivers and Harbors Act of 1899 (RHA) and Section 404 of the Clean Water Act. At present, USACE and other practitioners use a variety of field observations and desktop-based data sets, tools, and techniques to identify and delineate the lateral and longitudinal extent of USACE’s jurisdiction under the RHA for tidally influenced waters. Tidal waters, and thus federal jurisdiction under the RHA, “end where the rise and fall of the water surface can no longer be practically measured in a predictable rhythm.” However, the technical standards, definitions, and data to delineate tidal extent are also lacking. The uncertainty and ambiguity in what constitute tidal extent increases litigation risk and decreases repeatability and technical defensibility of USACE decisions. Nationally applicable technical guidance and rapid tools and techniques are needed to increase defensibility and consistency across all coastal USACE districts while also accelerating USACE Regulatory decision-making.

5 Aug 2024

Analysis of Beach Cusp Formation and Evolution Using High-Frequency 3D Lidar Scans

Abstract: Beach cusp characteristics were explored using 15 months of 3D lidar scans collected hourly at the Duck, NC, Field Research Facility. Fourier analyses performed on lidar-derived beach elevation contours generated spatial cusp spectra. Active cusp events identified from the location and magnitude of each spectrum’s peak were used to evaluate conditions during cusp formation and evolution. Cusps primarily developed during normally-incident, long-period, low-energy wave conditions with low frequency spread and reflective beach conditions. Often, however, persistent upper-beach cusps lasted days to months and dynamic lower-beach cusps evolved over individual tidal cycles. At times, beaches exhibiting multiple cusp systems reverted to a single cusp system extending the entire beach when the high-tide waterline reached the upper-beach cusps, with the location and spacing of the resulting lower-beach cusps controlled by the upper-beach cusps. This is consistent with a “morphological coupling” hypothesis that hydrodynamic-morphodynamic feedbacks between the swash and upper-beach cusps can form lower-beach cusps with a related wavelength as the tide falls. However, sometimes the high-tide waterline reaching the upper-beach cusps did not result in a unified beach state. This suggest that morphological coupling is often an important factor in controlling the development of new lower-beach cusps but cannot initiate cusp formation in hydrodynamic conditions outside those favorable for cusp activity.

14 Jun 2024

Application of Coastal Resilience Metrics at Panama City Beach, Florida

Abstract: This study, for the first time, combines the Coastal Engineering Resilience Index (CERI) and Buffer Width (BW) metrics to better understand the historic, current, and future resilience of the coastal system at Panama City Beach, Florida. After the construction of the US Army Corps of Engineers Coastal Storm Risk Management (CSRM) project at Panama City Beach, the CERI resilience metric has increased up to 21.3%, while negative storm impacts in the same have been less than 8%. The frequency of nourishment efforts moving forward is justified by a 24.3% increase in the BW metric when comparing cases that are nourished frequently with cases that are not nourished frequently. Moreover, there is a 129.2% increase in the BW metric when comparing the frequently nourished cases with the cases that are nourished only on an emergency basis. While the CERI and BW metrics have both been considered previously, their combined application provides an understanding of a broader temporal view of how storm events, CSRM projects, and nourishments have played a part in the resilience of the system at Panama City Beach over the last two decades and how they may play a role in the next half century.

11 Sep 2023

The Use of Native Vegetation and Natural Materials in Shoreline Stabilization: A Case Study of Bubble Gum Beach, Rehoboth Beach, Delaware

PURPOSE: This technical note is the fourth in a series about using native plant communities to achieve engineering and ecological purposes such as shoreline stabilization, structural enhancements, habitat creation, and ecosystem development. In this series, we demonstrate the utility of natural materials (specifically, native vegetation, oyster reefs, and coir logs) in living shoreline projects. Plant species and plant communities play critical roles in wave attenuation and sediment accretion in coastal areas. The application of vegetation in the coastal areas, especially on the East and Gulf Coasts, has focused heavily on the creation of living shorelines—serving both environmental and engineering purposes. This technical note documents the workshop conducted by the US Army Engineering Research and Development Center (ERDC) and hosted by the US Army Corps of Engineers’ (USACE) Philadelphia District (NAP) and Center for the Inland Bays. The goals of this technical note are (1) to demonstrate the application of native plant communities, oyster shells, and coir (coconut) materials and their installation techniques along shorelines to the engineering community; (2) to demonstrate how targeted vegetation establishment can facilitate ecosystem development along shorelines to improve engineering and environmental outcomes; and (3) to provide native vegetation installation techniques for living shorelines projects’ purposes.

8 Mar 2023

A Large-Scale Community Storm Processes Field Experiment: The During Nearshore Event Experiment (DUNEX) Overview Reference Report

Abstract: The DUring Nearshore Event EXperiment (DUNEX) was a series of large-scale nearshore coastal field experiments focused on during-storm, nearshore coastal processes. The experiments were conducted on the North Carolina coast by a multidisciplinary group of over 30 research scientists from 2019 to 2021. The overarching goal of DUNEX was to collaboratively gather information to improve understanding of the interactions of coastal water levels, waves, and flows, beach and dune evolution, soil behavior, vegetation, and groundwater during major coastal storms that affect infrastructure, habitats, and communities. In the short term, these high-quality field measurements will lead to better understanding of during-storm processes, impacts and post-storm recovery and will enhance US academic coastal research programs. Longer-term, DUNEX data and outcomes will improve understanding and prediction of extreme event physical processes and impacts, validate coastal processes numerical models, and improve coastal resilience strategies and communication methods for coastal communities impacted by storms. This report focuses on the planning and preparation required to conduct a large-scale field experiment, the collaboration amongst researchers, and lessons learned. The value of a large-scale experiment focused on storm processes and impacts begins with the scientific gains from the data collected, which will be available and used for decades to come.

31 Aug 2022

Current State of Practice of Nearshore Nourishment by the United States Army Corps of Engineers

Abstract: This US Army Corps of Engineers (USACE) special report prepared by the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, provides an overview of the current state of practice for nearshore nourishment with dredged sediment. This special report was completed with responses and input from professionals across the dredging and placement teams from each of the USACE Coastal and Great Lakes districts, providing comprehensive overviews of the decision trees these districts utilize in the placement of their dredged sediment. This report describes the general practice of nearshore nourishment, the impediments and concerns faced by nearshore nourishment projects, and the practical methods utilized by the Coastal and Great Lakes districts for their nearshore nourishment projects. Understanding the current state of practice, along with the general and specific impediments the districts face, enables further research in and development of best practices for use across the USACE and better communication of the practice to other stakeholders.

19 Jul 2021

Metrics of Success for Nearshore Nourishment Projects Constructed with Dredged Sediment

Purpose: This Regional Sediment Management Technical Note (RSM TN) provides practical metrics of success for nearshore nourishment projects constructed with dredged sediment. Clearly defined goals and performance metrics for projects will set clear expectations and will lead to long-term project support from local stakeholders and the public.

29 Jan 2021

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.