ADvanced CIRCulation Model

Simulations for Coastal Water Management

The US Army Corps of Engineers (USACE) is responsible for the design, operation, modification and maintenance of Federal inlet navigation channels, jetties and associated waterways. Accurate simulations of storm surge water levels and currents is critical in the design and operation of coastal storm risk management projects such as levees, floodwalls, dunes, beaches and wetlands. Comprehensive models of hydrodynamic simulations can support operational needs to minimize dredging, maintain channel reliability, manage inlet and adjacent beach sediment and predict navigation project performance.

Predictive Support for Storm Damage Reduction Projects

To model coastal circulation as well as storm surge water levels and currents in efforts to manage the impacts of storm damage, experts in hydrodynamic engineering at the ERDC Coastal and Hydraulics Laboratory (CHL) helped to develop the ADvanced CIRCulation Model (ADCIRC). Certified by the Federal Emergency Management Agency (FEMA) for use in performing storm surge analyses, ADCIRC is a hydrodynamic modeling technology that conducts short- and long-term simulations of tide and water surface elevations and velocities in deep ocean, continental shelves, coastal seas and small-scale estuarine systems. ADCIRC is a time-dependent unstructured finite element method hydrodynamic circulation model. ADCIRC maintains both accuracy and robustness when subjected to the wide range of scales of motion and hydrodynamic balances that exist when computing flows that transition from deep waters to flows in inlets, floodplains and rivers.

In a single simulation, ADCIRC can provide tide and storm surge elevations and velocities over a very large domain, encompassing regional domains such as the western North Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico and at the same time provide localized high resolution within an area of interest.

Typical ADCIRC applications include:

• Modeling tides and wind driven circulation
• Analysis of hurricane storm surge and flooding
• Dredging feasibility and material disposal studies
• Inlet sediment transport, morphology change and larval transport studies
• Support for nearshore military operations

Maximum Simulation Accuracy for Complex Environments

As an unstructured coastal ocean circulation model used to compute surface water elevation and currents, ADCIRC is typically used as a two-dimensional depth integrated (2DDI) model, but is also available as a three-dimensional (3D) model, to solve time dependent, free surface circulation and transport problems. The use of an unstructured mesh allows for high localized resolution where solution gradients maybe large, and lower grid resolution where solution gradients are small, minimizing both local and global error norms for a given computational cost.

ADCIRC simulates tidal circulation and storm surge propagation over large computational domains, eliminating the need for imposing approximate open-water boundary conditions that can create inaccuracies in model results, while simultaneously providing high resolution in areas of complex shoreline and bathymetry where it is needed to maximize simulation accuracy.

Targeted areas for ADCIRC application include continental shelves, nearshore coastal areas, inlets and estuaries. ADCIRC also includes these features:

• Wetting/drying of low-lying areas and overflow/throughflow barriers and bridge piers
• Wave radiation stresses and modeling salinity and contaminant transport
• 3D sediment transport/morphology change modeling and other sediment transport algorithms
• Spatially varying nodal attributes such as “Manning’s n”, “Surface Canopy” and “Surface Directional Roughness” values that allow for model parameterizations based on land cover and land use maps
• Compliant for model coupling via the Earth System Modeling Framework (ESMF)

Success Stories

ADCIRC has been successfully used in numerous high profile projects. Some recent applications of interest include:

• Hindcasting of major hurricane events such as Katrina, Ike, Sandy, Harvey, Irma, Maria and Ida
• Creation of tidal databases for extracting accurate tidal ranges
• Major regional storm surge and wave studies such as the North Atlantic Coast Comprehensive Study, the Coastal Texas Study, and the South Atlantic Coastal Study
• Water level adjustments for National Oceanic and Atmospheric Administration (NOAA) VDATUM (vertical datum) tool
• NOAA's Global Extratropical Surge and Tide Operational Forecast System (Global ESTOFS)
• Numerous military applications for the US Army, Navy and Marines around the world

Specifications

ADCIRC is a highly developed computer program for solving the equations of motion for a moving fluid on a rotating earth. These equations have been formulated using the traditional hydrostatic pressure and Boussinesq approximations and have been discretized in space using the finite element method and in time using the finite difference method.

• Elevation obtained from the solution of the depth-integrated continuity equation in Generalized Wave-Continuity Equation (GWCE) form
• Velocity obtained from the solutions of either the 2DDI or 3D momentum equations, retaining all nonlinear terms
• Operation runs with either a Cartesian or a spherical coordinate system
• GWCE solved using either a consistent or a lumped mass matrix and an implicit or explicit time stepping scheme
• In 3D, vertical diffusion is treated implicitly and the vertical mass matrix is not lumped, requiring the solution of a complex, tri-diagonal matrix problem over the vertical at every horizontal node
• Least squares analysis routines compute harmonic constituents for elevation and depth averaged velocity during the course of the simulation thereby avoiding the need to write out long time series files for post processing
• Optimized by unrolling loops for enhanced performance on multiple computer architectures and includes MPI library calls for high-efficiency (typically better than 90 percent) operation on parallel computer architectures

For more information about ADCIRC, including documentation, training and support, visit adcirc.org.