Development, Testing and Application of the Multi-Block LTFATE Hydrodynamic and Sediment Transport Model Earl J. Hayter See instructions for customizing these images on slide 3. Environmental Lab October 25, 2012

Innovative solutions for a safer, better world BUILDING STRONG ® LTFATE Multi-Block Hydrodynamic, Water Quality and Sediment Transport Modeling System LTFATE- HYDRO CH3D LTFATE-SED SEDZLJ STWAVE MET ADCIRC CE-QUAL-ICM

Innovative solutions for a safer, better world BUILDING STRONG ® LTFATE Multi-Block (MB) Concept  A conventional hydrodynamic single-block application approach typically requires long simulation time as well as large CPU memory requirements.  Solution: Grid Decomposition and Message Passing Interface (MPI) code.  Grid decomposition splits a single large grid into multiple smaller grids, MB, where each grid runs on it’s own CPU.  Message Passing Interface code allows communication amongst MB grids as the simulation proceeds.  Result: Significant decreases in simulation time and CPU memory.  To date, SEDZLJ applied in a 3D single block (SB) as a nested grid and 2D fully multi-block (MB) system 3

Innovative solutions for a safer, better world BUILDING STRONG ® Nested Grid SEDZLJ SB Application  The Mobile District is performing a feasibility study for channel widening of the Pascagoula Lower Sound (PLS) and Bayou Casotte (BC) navigation channels within the Mississippi Sound (MS). To support the District, ERDC modeled wave- and current-induced sediment transport in a portion of the MS centered about these channels.  Utilize fully 3D hydrodynamic and sediment transport modeling to evaluate the impact of the proposed widening alternatives sedimentation and infilling rates. Objective of Modeling Study

Innovative solutions for a safer, better world BUILDING STRONG ® Physical Setting Mobile Bay MS Sound Bayou Casotte Pascagoula River Chandeleur Islands

Innovative solutions for a safer, better world BUILDING STRONG ® Physical Setting Petit Bois Island Bayou Casotte Pascagoula River Horn Island Round Island

Innovative solutions for a safer, better world BUILDING STRONG ® Methodology ADCIRC and STWAVE used to generate the tidal boundary and local wave forcing for the Multi-Block (MB) LTFATE model. Performed circulation modeling of MS using MB LTFATE to generate hydrodynamic and salinity boundary conditions for the nested single block (SB) LTFATE model of the Pascagoula Lower Sound (PLS) and Bayou Casotte (BC) navigation channels within the Mississippi Sound (MS). Setup the sediment transport model using results from Sedflume and PICS analyzes and existing sediment data.

Innovative solutions for a safer, better world BUILDING STRONG ® Methodology (continued) Calibrate the sediment transport model by comparing model simulations with measured suspended sediment concentration (SSC) profiles. Validate the sediment transport model by comparing measured and simulated sedimentation volumes in the Lower Sound and Bayou Casotte reaches of the Pascagoula Harbor Channel. Simulate three channel widening scenarios to determine impact of the channel widening on the sedimentation volumes.

Innovative solutions for a safer, better world BUILDING STRONG ®  MB LTFATE-Hydro is a 3D, non-orthogonal boundary-fitted hydrodynamic model that includes temperature and salinity transport.  MB boundary conditions are river inflow data and tidal forcing from ADCIRC circulation model simulations and time varying wave forcing from STWAVE.  MB LTFATE system provides time varying water surface elevation, flow, and salinity forcing for the SB open-water boundaries.  SEDZLJ is the sediment transport model that is dynamically integrated into the LTFATE hydrodynamic module. MB-SB LTFATE

Innovative solutions for a safer, better world BUILDING STRONG ® Multi-Block (5) LTFATE Grid

Innovative solutions for a safer, better world BUILDING STRONG ® Nested SB LTFATE Bathymetry PLS Channel BC Channel

Innovative solutions for a safer, better world BUILDING STRONG ® Nested SB LTFATE GRID

Innovative solutions for a safer, better world BUILDING STRONG ® Sediment Transport Processes Simulated in LTFATE Erosion of mixed cohesive and non-cohesive sediment beds Advective and dispersive transport of suspended sediment Bedload transport of non-cohesive sediment Settling of flocculated cohesive sediment, and settling of individual non-cohesive sediment particles. Effect of bed slope on bedload transport and erosion rate is represented. Changes in bottom elevations due to erosion and deposition are accounted for in calculating the flow field during the next model timestep. Current- and wave-induced bed shear stresses are calculated and used in determining erosion rate.

Innovative solutions for a safer, better world BUILDING STRONG ® Sediment Transport Model Simulations LTFATE was run for the same two month time period for the three widened channel configurations. The ratio of sedimentation volumes of the widened channels to those of the existing channel are given below. Expansion Width Bayou Casotte Channel Pascagoula Lower Sound Channel 75’ East & 75’ West ’ West ’ West1.21.4

Innovative solutions for a safer, better world BUILDING STRONG ® SB Summary  3D sediment transport modeling was performed in the MS Sound using a combination of MB and SB LTFATE, which is a state-of- the-art hydrodynamic, salinity, temperature and sediment transport modeling system.  LTFATE can represent the following forcings: time varying water surface elevation due to tides, riverine flows, wind, and spatially and temporally varying wave properties. The latter are used to calculate radiation stresses that are included in the momentum equations solved in LTFATE.  The effect of bed slope on bedload transport and erosion rates is accounted for in LTFATE. Representing the impact of bed slope becomes critical at navigation channels due to relatively rapid changes in bathymetry.

Innovative solutions for a safer, better world BUILDING STRONG ® MB SEDZLJ Development  ERDC has further developed the MB LTFATE to dynamically link SEDZLJ within the MB system by developing MPI routines to allow SEDZLJ to be run in every block.

Innovative solutions for a safer, better world BUILDING STRONG ® Questions?