Simulations for Storm Water Management

The US Army Corps of Engineers (USACE) is responsible for the design, modification, operation, and maintenance of Federal inlet navigation channels, jetties, and associated waterways. Prediction of potential storm surge water levels is critical in the design of flood and storm damage reduction projects and protection of facilities and infrastructure and beneficial to planning and evacuation of low-lying areas if a storm event occurs. Comprehensive models of hydrodynamic simulations can support operations and maintenance and help minimize dredging, maintain channel reliability, manage inlet and adjacent beach sediment, and predict navigation project performance.

Predictive Support for Storm Damage Reduction Projects

To predict storm surge water level and help control the impact 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 storm surge elevations and velocities in deep-ocean, continental shelves, coastal seas, and small-scale estuarine systems.

In a single simulation, ADCIRC can provide tide and storm surge elevations and velocities corresponding to each node over a very large domain, encompassing regional domains such as the western North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico.

Typical ADCIRC applications include the following:

• 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
• Nearshore marine operations

ADCIRC is a finite element, time-dependent, long wave, hydrodynamic circulation numerical model for the simulation of water level and current over an unstructured gridded domain. ADCIRC maintains both accuracy and robustness when applied to the wide range of scales of motion and wide range of hydrodynamic balances that exist when computing deep-ocean flows that transition to flows in inlets, floodplains, and rivers.

Maximum Simulation Accuracy for Complex Environments

As an unstructured coastal ocean circulation model used to compute surface water elevation and currents, ADCIRC runs as a two-dimensional depth integrated (2DDI) model or as a three-dimensional (3D) model to solve time-dependent, free surface circulation and transport problems. The use of an unstructured grid allows for high localized grid resolution where solution gradients are large and low 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 “Surface Canopy” and “Surface Directional Roughness” that allow for modifications of wind inputs based on land use maps

Success Stories

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

• Hindcasting of Hurricane Katrina for the USACE Interagency Performance Evaluation Task Force report
• Creation of tidal databases for extracting accurate tidal ranges
• The Louisi­ana Coastal Protection and Restoration Project for redesigning the flood protection system for New Orleans
• Adjustments for National Oceanic and Atmospheric Administration VDATUM (vertical datum) tool
• 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 (via a compiler flag) and an implicit or explicit time stepping scheme (via variable time weighting coefficients)
• 2DDI momentum equations are lumped and require no matrix solver. 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 routine computes harmonic constituents for elevation and depth-averaged velocity during the course of the run thereby avoiding the need to write out long time series 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.

ERDC Points of Contact
Questions about ADCIRC?
Contact: Chris Massey
Email: Chris.Massey@usace.army.mil
Phone: 601-634-2406