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.

1 Oct 2020

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.

20 Aug 2020

PUBLICATION NOTICE: Evaluating Collection Parameters for Mobile Lidar Surveys in Vegetated Beach-Dune Settings

Purpose: The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to compare collection parameters and gridding techniques for mobile lidar surveys of beach-dune systems in the northern Outer Banks, NC.

13 May 2020

PUBLICATION NOTICE: Technical Feasibility of Creating a Beach Grain Size Database with Citizen Scientists

ABSTRACT:  The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to investigate the feasibility of collecting beach grain size information with images collected by citizen scientists to build a globally accessible database. Engaging citizen scientists in scientific information collection through crowdsourcing has become a more popular and cost-effective way to collect large amounts of data while increasing interest in the research through public engagement (Irwin 2018). Citizen scientists equipped with their personal smartphones allow for very large datasets to be collected that would otherwise be financially or logistically impossible. Additionally, it provides an opportunity to educate and engage the general public.

23 Apr 2020

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.

23 Apr 2020

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.