CONCLUSIONS - doere100010

ERDC TN-DOER-E10

April 2000

As noted, either a boundary-fitted grid can be imported or a rectangular land-water grid can be

generated by SSFATE. For the case of a rectangular grid, the user can apply the suspended sediment

fate model in any subdomain of the location area selected. The user identifies the subdomain of

interest through its corner points and selects the appropriate grid size. A gridding algorithm is then

used to generate a land-water rectangular grid system.

When the rectangular grid is generated, the user may edit the computer-produced grid to better

conform to the shoreline or represent openings to restricted passages (e.g., between islands, narrow

inlets, etc.). Editing is also useful to add features that are not given on the base map. Once completed,

a bathymetric file is automatically generated and stored under a user-selected grid file name.

Multiple grid files can be made to define different areas or the same area with various modifications.

SSFATE requires a flow field for execution of the particle tracking computations. As previously

discussed, such a flow field can be generated or painted using limited field data (not a mass

conservative field) or can be imported as output from a 3-D numerical hydrodynamic model on a

boundary-fitted grid.

Model output includes animation of the particles representing each sediment type individually or

all of the particles together. A typical snapshot from an animation of suspended sediment particles

being transported away from a dredging site is presented in Figure 3. The output display system is

designed so that the user can interact with the display window at any time during the trajectory view

operation to obtain information on mass balance for a selected size class of particles. Additional

model output includes both horizontal and vertical concentration contours of each sediment type or

a superposition of all suspended sediment, time-series of suspended sediment concentrations at a

particular point, spatial distribution of sediment deposited on the sea bottom, and tabular summaries

of how much sediment is in suspension, how much has been deposited, and how much has left the

grid. A contouring procedure is available to provide dredged material thickness distributions on

the sea bottom and concentrations at user-defined depths in the water column. The user may select

the contour intervals and threshold value. The user can interact with the contoured data to obtain

pertinent information such as a cross-sectional view along a user-selected transect, the distance to

features from the sediment source, and the area covered by material that has been deposited on the

bottom.

CONCLUSIONS: A personal computer based modeling system called SSFATE for computing

suspended sediment concentrations resulting from dredging operations has been presented and its

major components have been described. SSFATE can be used anywhere in the world and provides

an integrated and unified system to support data display, model application, and interpretation of

results.

SSFATE has been developed to satisfy a specific need for tools to aid in negotiation of environmental

windows. Predetermined attributes of such a tool included adaptability to a broad spectrum of

dredging project scenarios, low "front end" requirements for input data or supporting hardware,

efficient computational algorithms to enable multiple simulations in a short period of time, and

effective means of output visualization. The strengths of SSFATE are in its versatility, simplicity,

efficiency, and low cost of operation. In tandem with other tools being developed under the auspices

of the DOER Program Environmental Windows Focus Area (e.g., FISHFATE, see Ault, Lindeman,