TOPIC 4A: An Open-Source Community Model for Coastal Sediment Transport

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4A: An Open-Source Community Model for Coastal Sediment Transport

Community Sediment Transport Model

Lead PI: Dr. W. Rockwell Geyer, Woods Hole Oceanographic Institution

This proposal seeks support for a three-year effort to build an open-source community sediment-transport model. The need and value for such a model has been well established by previous NOPP-supported planning efforts (Sherwood et al., 2000; 2002) and the feasibility of the proposed approach has been demonstrated by incorporation of sediment-transport and morphology algorithms into the ONR-supported Regional Ocean Modeling System (ROMS).

The goal of this project is to produce an open-source model that couples hydrodynamics (circulation and waves), sediment transport, and morphodynamics. The model will be suitable for realistic and useful simulations of processes that influence sediment transport in the coastal ocean, including estuaries, nearshore regions, and the continental shelf over regional length scales (10’s of meters to 100’s of kilometers) and time scales ranging from transport events to decades. The code will be written in modern, portable languages (mostly FORTRAN95) using a modular approach that will allow flexibility and extensibility. In addition to the source code (which will have an open-source license and run on most computer systems from laptops to multi-processor clusters), the project will provide model documentation, training, test cases, tools for processing model input and output, and demonstrated applications.

The community model will actually be a system of modules coupled using the Earth System Modeling Framework. This framework is funded by NASA, DoD, and NSF and is designed to integrate geophysical models at multiple scales on multi-threaded computer architectures. ESMF is being used by NRL, other Federal agencies, and universities to couple atmospheric and ocean models. The proposed model will include interchangeable modules built from existing models. One set of hydrodynamic modules will be derived from the existing USGS community sediment-transport model that resolves the circulation with ROMS and the waves with SWAN (Fig. 1). A second set of hydrodynamics modules will be the product of the USACE MORPHOS project, which presently uses ADCIRC as the circulation model and STWAVE as the wave model. When this project is complete, users will have the option of choosing from at least two different sediment-transport modules and two different morphology modules coupled with the desired hydrodynamics modules. The project will benefit from ongoing theoretical, numerical, and observational efforts devoted to improving our fundamental understanding of sediment transport. Investigations with high-resolution models (i.e. RANS and LES models of flow and sediment transport; Boussinesq models of waves) will provide parameterizations of key processes (e.g., bottom dissipation, wave shoaling) required in the regional scale model. Specifically, we plan to incorporate improved treatments of wave-current interactions in regions of shoaling waves, sediment-induced stratification and momentum transfer (e.g., fluid-mud layers), erosion and deposition across the sediment water interface, mass fluxes of water and sediment at the lateral boundary of the model (e.g., swash zones), and optical properties of water affected by sediments.

At each stage in the model development, working models will be available to the broader research community. Great emphasis will be placed on developing standards and conventions for the exchange of data, model grids, model input and output, and module definitions and interfaces, with the goal of establishing and working with a common framework for earth system modeling. Software for preparing model input and analyzing output will be built using emerging conventions for web-based file access and an open-source, platform-independent approach. A collaborative web site, tutorials, and public training sessions will be used to extend the development community beyond the researchers funded here and leave a legacy of an actively evolving sediment-transport modeling system.

The team assembled to develop this modeling system includes key Federal agencies involved in coastal sediment-transport issues (ONR, USACE, NRL, and USGS) and a collection of leading academic and government researchers from the U.S. and Europe. The team has a carefully designed distribution of sediment-transport scientists, physical oceanographers, modelers, software engineers, and model users. The components we have chosen as the basis for model development are working models that represent the state-of-the-art in U.S. coastal circulation, wave, and sediment-transport processes, and that are the result of years of investment by the NOPP partner agencies including ONR, NSF, USGS, and USACE.

Number of Years: 3

Funding Requested: $2,692,297 (87.2% domestic, 12.8% foreign)

Partners: