DUNEX Modeling Waves, Water Levels, Sediment Transport, and Shoreline Change

USGS DUNEX Operations on the Outer Banks

USGS DUNEX Operations on the Outer Banks

DUring Nearshore Event eXperiment (DUNEX)  is a multi-agency, academic, and non-governmental organization (NGO) collaborative community experiment designed to study nearshore coastal processes during storm events.

DUNEX Home Page

Tools and Software

Numerical models that represent the physical processes of the coastal ocean, such as waves, tides, currents, and sediment transport, allow us to fill in the observational dataset gaps in space or time. 

COAWST Modeling System Manuscript

COAWST Git Repository

COAWST Forecast

CoastSat Toolbox GitHub Repository

CoastSat Toolkit Manuscript

Science Center Objects

Large, collaborative field experiments such as DUNEX leverage observations of the coastal ocean made by multiple academic, agency, and NGO teams, providing the opportunity to grasp a broader picture of the forces responsible for coastal change. Despite deployment of many instruments, it’s impossible to measure everything, everywhere, at all times. Numerical models that represent the physical processes of the coastal ocean, such as waves, tides, currents, and sediment transport, allow us to fill in the observational dataset gaps in space or time. Numerical models can also be controlled to investigate specific physical processes to test hypotheses or compare to observations.  

Numerical models are composed of a suite of mathematical equations that attempt to completely describe or estimate physical processes. For DUNEX, we will use a numerical model called COAWST to: 

1) predict coastal ocean conditions during the experiment to support other scientists and 

2) hindcast coastal ocean conditions and morphological changes during past storm events that were measured during the experiment.  

COAWST is the Coupled Ocean-Atmosphere-Wave-Sediment Transport modeling system, which links several models together to simulate forces such as waves and tidal currents and the interactions between them. COAWST has been developed at the USGS in collaboration with academic and other agency partners and has been used to study a wide range of interesting coastal ocean problems, such as rip currents, barrier island breaching, and estuarine circulation. 

The forecast of coastal ocean conditions provided by COAWST give our USGS team and other DUNEX scientists information to assist with instrument deployments and surveying. It can also provide an initial dataset to compare against field observations or provide context.  

After the experiment, we will hindcast particular storm events, or the quiescent periods in between storms, at very high spatial resolution (1-10 m) to investigate physical processes controlling coastal change. For example, wave breaking controls, in part, wave runup on the beach, surf zone circulation and mixing, and sediment transport in the nearshore. In collaboration with scientists collecting field data, we will evaluate and improve the model parameterizations that describe wave evolution in the nearshore. Additionally, we will explore the exchange of sand between the dune, beach, and nearshore, and the various conditions responsible for sand transport.  

schematic of a ocean modeling system that shows different parts

Overview of the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that couples model components representing different earth systems, such as the Weather Research and Forecasting (WRF) model, the Simulating Waves Nearshore (SWAN) model, the Regional Ocean Modeling System (ROMS), and the Community Sediment Transport Modeling System (CSTMS). The models are coupled using the Model Coupling Toolkit (MCT). (Credit: Zafer Defne, Woods Hole Coastal and Marine Science Center. Public domain.)

maps showing a model forecast of ocean water levels, waves, currents, and sediment

Using COAWST, we forecast water levels, waves, currents, sediment, and other ocean variables such as temperature and salinity. Ocean dynamics are simulated at coarse resolution (5 km) over the entire North Atlantic Ocean and simulated at high resolution (200 m) along the northern Outer Banks. (Credit: Christie Hegermiller, Woods Hole Coastal and Marine Science Center. Public domain.)

As part of DUNEX and the Hurricane Florence Supplemental Project the USGS is also conducting large-scale, long-term coastal change modeling with the aid of satellite-derived, historical shoreline observations.  Satellite-derived shoreline positions (based on the CoastSat toolbox of Vos et al. 2019) are assimilated into the CoSMoS-COAST shoreline model (Vitousek et al. 2017, 2021) to produce a calibrated, site-specific hindcast of shoreline change in response to storms.  The calibrated model is then run with future wave conditions to produce a forecast of coastal change from days to decades.  The integrated modeling system demonstrates excellent agreement when compared with traditional survey data at Ocean Beach, California where the model is currently working. The DUNEX experiment will test the performance of the integrated modeling system on the U.S. east coast from Florida to Virginia. 

a terrain image of a barrier island has a graph with a blue line showing change in shoreline position extending from a red line

An example of satellite-derived shoreline observations data using the CoastSat toolbox (Vos et al. 2019) at 50 m-spaced transects in Duck, NC. (Credit: Jin-Si Over, Woods Hole Coastal and Marine Science Center. Public domain.)