A process-based parametric closure model for estimating cross-shore sediment transport (CST) rate has been developed for simulating long-term shoreline evolution. The formulations of this closure model include calculations of various subaqueous cross-shore transport components induced by waves, currents, and gravity. To better calculate asymmetrical near-bed orbital velocity that is a key to predict the cross-shore transport rate in the nearshore zone, a nonlinear wave-shape model is adopted. By formulating wave nonlinearity to cross-shore transport, this closure model can predict the net on- and offshore transport rates in response to shoreline accretion and erosion driven by waves and currents during low- and high-energetic conditions. This new capability for cross-shore shoreline change has been implemented into a one-line model, primarily driven by longshore sediment transport (LST). Calibration of model parameters and model validation were performed by simulating shoreline changes for a 5 km section of coastline in Duck, North Carolina, over a 14-year period from 2000 to 2013. The simulation results reproduced seasonal shoreline recoveries during low-energetic fair weather and also captured rapid retreats during storms. This shoreline model with inclusion of LST and CST has significantly improved the prediction accuracy of long-term shoreline changes at the study site. Impact analysis of a pier located within the domain reveals that this shoreline model with CST can better simulate sediment bypassing through the structure that depends on multiple local variables such as shoreline positions, updrift longshore transport, waves, and water levels. Therefore, this new shoreline model will facilitate long-term management of sediments and shoreline erosion and impact assessment of coastal structures.

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.

This report documents a numerical modeling study investigating sediment transport and morphology change adjacent to Merrimack Inlet, Newburyport, and nearshore in the vicinity of Salisbury Beach and Plum Island, Massachusetts. Concerns at the site include beach erosion, shoreline retreat on Plum Island downdrift of and within the inlet, and reduced navigability of the inlet. The numerical modeling evaluation consists of two phases. The Phase I study was conducted with the damaged and partially rehabilitated South Jetty between 2012 and 2014, and the Phase II study was conducted with the fully rehabilitated South Jetty between 2015 and 2016. Historical hydrodynamic and sediment data in the study area were assembled, and a field data collection program was carried out. The datasets were used to develop a coastal wave, hydrodynamic, and sediment transport model. Different alternatives were developed to evaluate sediment management strategy and structure modification, and the calculated bed sediment volume changes of each alternative were compared with the results under base (existing) condition. Alternative simulations demonstrated the Coastal Modeling System capability in evaluating beach erosion, structure performance, sediment transport, and morphology change in the inlet and estuarine system. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CHL TR-18-7 iii

Prediction of long-term shoreline changes plays an important role in planning and management of coastal zones and regional sediment management. Quantifying uncertainties of shoreline evolution and risks of extreme shoreline changes (erosion and accretion) is a key task for practicing best shoreline protection. Due to complex natural features of offshore waves, sediment transport in alongshore and cross-shore directions, and sea level rise, prediction of long-term shoreline changes is a challenge. This paper presents a probabilistic shoreline change prediction model to quantify uncertainties of shoreline changes in response to waves and sea level rise (scenarios) by using Monte Carlo simulations (Fig. 1). A USACE shoreline evolution model, GenCade (Frey et al. 2012), is used to simulate shoreline changes driven by longshore and cross-shore sediment transport due to offshore wave action. A set of probability density functions are developed to represent stochastic features of waves (i.e. heights, periods, and directions) under both fair weather and extreme weather conditions. The newly-developed capabilities of the model are examined by predicting probabilities of shoreline changes in an idealized coast with and without coastal engineering conditions (e.g. installation of hard structures and beach fill/nourishment) (Fig. 2). Applicability of the model is also demonstrated by reproducing shoreline changes in a period in a coast in Duck, NC, USA. It also includes a maximum likelihood estimation to predict long-term extreme shoreline changes (particularly shoreline retreat) in terms of return periods (years) (Fig. 3). Predicted uncertainties of long-term shoreline changes can facilitate the best engineering practice for design and management of shorelines and coasts.

This study aims to predict probabilistic shoreline evolution in response to sea level changes, land subsidence, and onshore sand transport by using Monte Carlo simulation approach. A shoreline evolution model, GenCade, is used to simulate longshore sediment transport and long-term shoreline changes induced by random offshore waves. To determine landward sediment transport and shoreline responses to sea level changes, a modified Bruun rule is implemented into the GenCade model. The other two terms for long-term shoreline changes are also implemented into the GenCade model. A probability density function is used to capture stochastic features of wave heights under both fair weather and extreme weather conditions. It produces time series of wave heights including small and extreme waves based on their probabilities (or frequencies of appearance). A long-term shoreline changes in a hypothetical beach are simulated by considering wave climates, sea level change scenarios, land subsidence, and onshore transport. Probabilistic shoreline changes are computed by using the GenCade and Monte Carlo simulations.

Prediction of long-term shoreline changes is a key task in planning and management of coastal zones and regional sediment management. Due to complex natural features of offshore waves, sediments, and longshore sediment transport, quantifying uncertainties of shoreline evolution and risks of extreme shoreline changes (erosion and accretion) is of vital importance for practicing uncertainty- or risk-based design of shorelines. This paper presents probabilistic shoreline change modeling to quantify uncertainties of shoreline variations by using numerical-model-based Monte-Carlo simulations. A shoreline evolution model, GenCade, is used to simulate longshore sediment transport and shoreline changes induced by random waves from offshore. A probability density function with a modified tail distribution is developed to capture stochastic features of wave heights under fair weather and storm conditions. It produces a time series of wave heights including small and extreme waves based on their probabilities (or frequencies of appearance). Probabilistic modeling of shoreline change is demonstrated by computing spatiotemporal variations of statistical parameters such as mean and variance of shoreline changes along an idealized coast bounded by two groins. Maximum shoreline changes in return years with a confidence range are also estimated by using maximum likelihood method. Reasonable results of obtained probabilistic shoreline changes reveal that this model-based Monte-Carlo simulation and uncertainty estimation approach are applicable to facilitate risk/uncertainty-based design and planning of shorelines.

This paper presents a probabilistic approach to quantify uncertainties of shoreline changes (accretion and erosion) by using Monte Carlo simulations. A shoreline evolution model, GenCade, is used to simulate longshore sediment transport and shoreline changes induced by random waves from offshore. A probability density function is developed to capture stochastic features of wave heights under both fair weather and extreme weather conditions. It produces time series of wave heights including small and extreme waves based on their probabilities (or frequencies of appearance). This will generate uncertainties in prediction of annual maximum shoreline erosions in different return periods (years). The developed Monte Carlo Model for GenCade can be used to assess reliability and uncertainty of prediction in shoreline changes in natural coasts.

: The Coastal and Hydraulics Laboratory, Engineer Research and Development Center, and the U.S. Army Engineer District, Galveston, conducted a study to support a sand management strategy for the Galveston Park Board of Trustees of Galveston, TX. The long-term management strategy encompasses not only Galveston Park Board of Trustees managed areas, but the entire shoreline of Galveston Island. In the first phase of the project, a sediment budget was recomputed and GenCade, a numerical model, was calibrated for Galveston Island. After discussing potential solutions and actions with the Park Board, engineering analyses and numerical modeling were conducted to quantify the performance of each selected alternative. The long-term solution is a wide beach along Galveston Island that is filled through beach nourishment and backpassing plants on both ends of the island. This solution will require a large volume of sand for the initial construction; therefore, sand management solutions were identified and potential offshore sand sources were identified. Shorter-term and smaller-scale beach nourishment activities were also provided as options within the strategy.

Purpose: This Coastal and Hydraulics Engineering Technical Note (CHETN) provides guidance for simulating dredging of inlet shoals and associated placement of beach fills in GenCade. Applications of beach fills and dredging represent the majority of GenCade simulations and alternatives. This CHETN describes basic theory, setup, and applications of beach fills and dredging and is intended to explain how GenCade can be used to help District users answer questions about these types of applied engineering studies. Idealized applications of a single beach fill, an inlet with dredging and placement updrift and downdrift, and an inlet with dredging but sand removed from the model are described. Present model limitations are also discussed. The reader is referred to Frey et al. (2012, 2014) and Munger and Frey (2015) for additional information about the GenCade model.

: A sediment budget was developed for the U.S. shoreline of Lake Erie from Maumee Bay, OH, to Buffalo, NY, covering four time frames: (a) Pre-Armoring of the shoreline (1860s1930s), (b) Mid-Century (mid-twentieth century, 1930s1970s), (c) Recent era (1970s2000s), and (d) Future expected conditions (2010+). Sources of data included historic U.S. Army Corps of Engineers Lake Survey charts, aerial photographs, and lidar survey data. The Ohio Department of Natural Resources provided historical recession lines for Ohio. The Pennsylvania Department of Conservation, Natural Resources, and the U.S. Geological Survey supplied historical bluff lines for Pennsylvania. Analysis of harbor sedimentation and sediment bypassing provides verification of the volume of sediment calculated from bluff recession measurements. These volumes were consistent with harbor sedimentation or sediment bypassing measurements at most points along the shoreline, with the exception of under predicting sediment volumes at Fairport Harbor, OH. Most reaches show a decrease in bluff-supplied sediment over time. The decrease is a result of greater bluff armoring during the twentieth century, particularly after the 1970s. For New York and eastern Pennsylvania, the future projected sediment supply from bluffs is similar or slightly less than from the recent era. But in Ohio, the future supply is projected to decrease in most areas because of the almost complete armoring of the Ohio shore. For the predicted future conditions, total eroded bluff volume will range from 15,000 cubic meters per year in Erie County, NY, to 200,000 cubic meters per year in Ashtabula County, OH.

: This Special Report is a condensed version of previous technical reports describing the shoreline change model GenCade. It is meant to provide new and prospective users of GenCade a starting point to learn the model. While no new topics are presented, important information which would otherwise be distributed among several publications is conveniently grouped in one shore document. The first part of the report describes the basic features of the model and its suitability to a range of applications to help prospective users decide if GenCade is the right tool for a specific project. The second part of the report is a quick start guide with step-by-step instruction on how to build a GenCade project. Each topic presented in this publication is accompanied by a list of references that provide more in depth information.

: Galveston Island is a major tourist and commercial center on the Gulf of Mexico at the mouth of Galveston Bay, Texas, USA. The shoreline along the Galveston Seawall regularly requires beach nourishment while the beach west ofthe Seawall has severely eroded. In order to protect the island and ensure it is available for generations to come, a 50-year sediment management plan was developed. A sediment budget using the Sediment Budget Analysis System was calculated and numerous alternatives were simulated with GenCade, a shoreline change and sand transport model. Finally, several alternatives ranging from no action to a comprehensive beach fill and backpassing system are presented as partof the sediment management plan.

A Conceptual Regional Sediment Budget (CRSB) was developed for coastal beaches, bays and estuaries extending from Virginia to Maine, USA, as part of the North Atlantic Coast Comprehensive Study. Hurricane Sandy made landfall on October 30th, 2012 near Brigantine, New Jersey and generated severe beach erosion and property damage throughout this region. A CRSB is the first step in understanding sediment transport patterns and magnitudes, and aligning dredging and placement operations to take advantage of natural processes and identify sediment deficiencies in a regional system. Optimizing regional sediment management practices in this region is critical to (a) improve beneficial use of dredged sediments; (b) reduce the risks of future storm damage and enhance the environment; and (c) reduce costs in maintaining coastal infrastructure. Data from 1990-2013 indicated an average of 18.7 million cu yd/year was dredged within the North Atlantic region. The CRSB is accessible via a web portal.

: Net sediment transport in the littoral cell extending from Michigan City Harbor, IN, to Burns Waterway Harbor, IN, USA, is from east to west. For the four decades following construction of the Burns Waterway Harbor, net transport averaged about 190,000 yd3/year. Of this amount, accumulation in the fillet east of the Arcelor-Mittel bulkhead was 106,000 yd3/year, while dredging from the Bailly Generating Station cooling water intake was 83,000 yd3/year. The total transport calculated in this study is higher than most published previous estimates. The volume of sediment now bypassing the lakeward end of the bulkhead and entering the Federal harbor is estimated to be 84,000 yd3/year. This value will have to be confirmed from dredging statistics in the future. An average of 61,000 yd3/year of sand has been placed both on beaches at the National Park Service West Beach Unit west of Portage/Burns Waterway and offshore at Ogden Dunes. Full bypassing should to be about three times this amount to equal the longshore transport value of about 190,000 yd3/year.

Abstract : This report documents development of a Conceptual Regional Sediment Budget (CRSB) for the US Army Corps of Engineers (USACE) North Atlantic Division (NAD). The NAD requested preparation of a CRSB as part of the post-Hurricane Sandy assessment to provide information about sediment sources and opportunities for strategic placement of sediment within the Division. Development of a detailed working sediment budget is fundamental to better sediment management. A conceptual sediment budget is the first phase in development of the working budget, and is intended to provide a general framework based on existing transport information from which a more detailed sediment budget can be later prepared based on rigorous data analysis and numerical modeling. For this CRSB, existing literature and databases were reviewed and analyzed to characterize sediment transport pathways and magnitudes, and morphologic zones of erosion and accretion. The CRSB highlights areas with data gaps, conflicts in existing budgets, and opportunities for better sediment management within the NAD and is available via a Geographic Information System (GIS) portal.