Theoretical Assumptions and Limitations

Cvr-Chpt8
Page Navigation
4

Restoration Research Program. The conception and initial development of the

package were the results of the efforts of William A. Thomas, Ronald R.

Copeland and Nolan Raphelt. However, many workunits and many principal

investigators have contributed to the package. The US Government is not

responsible for results obtained with this software. However, the office

supporting the package would welcome documentation of program errors and

should respond if fiscally feasible.

Files

The program operates interactively. However it saves the input data in an

ASCII files and uses these files to pass data from module to module.

Theoretical Assumptions and Limitations

SAM is not a package of one-dimensional models. SAM makes calculations

based on one cross section at one point in time. There are no provisions in any of

the modules for simulating the effects of a hydrograph nor for looking at a reach

of a river, except as it might be represented by an average. SAM is designed to

be used as a tool during reconnaissance level planning studies. Broad application

of SAM results must be made with caution.

Sediment transport functions in SAM must be used with care. Essentially,

SAM.sed applies the sediment transport functions at a point, which allows for no

variability in the size class distribution over time or space. Considering that the

size class distribution of bed material in the natural river changes with discharge,

reach, time of year, and other temporal factors, SAM's use of a fixed, non-

varying, as-prescribed size class distribution for all calculations presents the

possibility that the calculated transport rates are not truly representative of the

natural river. The procedure in HEC-6, which integrates processes over several

cross sections which describe a reach of the river and provides a continuity

equation for sediment movement, will consequently produce a more reliable

result than comes from applying a sediment transport function at a single point.

Chapter 1

Introduction