Model Output

Model Output

The output starts by echoing the input data and then optionally presenting the

time history of the descent and collapse phases. In descent history, the location

of the cloud centroid, the velocity of the cloud centroid, the radius of the hem-

ispherical cloud, the density difference between the cloud and the ambient water,

the conservative constituent concentration, and the total volume and concentra-

tion of each solid fraction are provided as functions of time since release of the

material.

At the conclusion of the collapse phase, time-dependent information concern-

ing the size of the collapsing cloud, its density, and its centroid location and

velocity as well as contaminant and solids concentrations can be requested. The

model performs the numerical integrations of the governing conservation equa-

tions in the descent and collapse phases with a minimum of user input. Various

control parameters that give the user insight into the behavior of these computa-

tions are printed before the output discussed above is provided.

At various times, as requested through input data, output concerning sus-

pended sediment concentrations can be obtained from the transport-diffusion

computations. With Gaussian cloud transport and diffusion, only concentrations

at the water depths requested are provided at each grid point.

For evaluations of initial mixing, results for water column concentrations can

be computed in terms of milligrams per liter of dissolved constituent for Tier II

evaluations or in percent of initial concentration of suspended plus dissolved

constituents in the dredged material for Tier III evaluations. The maximum

concentration within the grid and the maximum concentration at or outside the

boundary of the disposal site are tabulated for specified time intervals. Graphics

showing the maximum concentrations inside the disposal-site boundary and

anywhere on the grid as a function of time can also be generated. Similarly,

contour plots of concentration can be generated at the requested water depths

and at the selected print times.

Target Hardware Environment

The system is designed for the 80386-based processor class of personal com-

puters using DOS. This does not constitute official endorsement or approval of

these commercial products. In general, the system requires a math coprocessor,

640 KB of RAM, and a hard disk. The STFATE executable model requires

about 565 KB of free RAM to run; therefore, it may be necessary to unload net-

work and TSR software prior to execution. The model is written primarily in

Fortran 77, but some of the higher level operations and file-management opera-

tions are written in BASIC; some of the screen control operations in the

Fortran 77 programs are performed using an Assembly language utility program.

Appendix D Short-Term Fate of Dredged Material Model