6.6. OTHER MOVABLE-BED MODEL ASPECTS
321
92-m-long offshore breakwater or a 184-m-long offshore breakwater would
be ineffective at curbing shoreline erosion, but a 366-m-long shore-parallel
breakwater attached to the jetty appeared to be a viable and effective shore
protection option.
6.6 Other Movable-Bed Model Aspects
6.6.1 Model Verification
The unknowns involved in predicting sediment transport translate into uncertainties in our ability to model sediment transport at reduced scale. Previous sections in this chapter have examined some of the theoretical and
empirical approaches to this difficult “art”. Because movable-bed modeling
is not as well established as hydrodynamic modeling,
Verification of the model is probably the single most
important aspect of conducting movable-bed modeling
studies.
Model verification should be the first task performed after the model has
been designed and constructed because the verification phase may alter how
the model is run. For example, sometimes morphological time scales differ
from the hydrodynamic time scale, and therefore, can only be determined
in the calibration or verification phase. In a few instances, such as twodimensional storm erosion on a beach profile17, verification of the modeling
criteria has already been accomplished in general, and the model results
can be taken as valid without additional specific verification.
Hudson, et al. (1979) listed the following as essential prototype data for
use in three-dimensional movable-bed model verification for coastal studies.
a. Detailed sediment-size distribution over the entire area of
interest
b. Computational estimates of yearly and monthly net longshore transport based on wave statistics, refraction, etc.
c. All available survey data
d. Accurate wave and sediment transport measurements
Of course, reality has its way of assuring that the available prototype
data will not be as complete as hoped, and so the engineer must make optimum use of what data are available. The requirement of reliable prototype
7 See Hughes and Fowler (1990b) for validation.
321
92-m-long offshore breakwater or a 184-m-long offshore breakwater would
be ineffective at curbing shoreline erosion, but a 366-m-long shore-parallel
breakwater attached to the jetty appeared to be a viable and effective shore
protection option.
6.6 Other Movable-Bed Model Aspects
6.6.1 Model Verification
The unknowns involved in predicting sediment transport translate into uncertainties in our ability to model sediment transport at reduced scale. Previous sections in this chapter have examined some of the theoretical and
empirical approaches to this difficult “art”. Because movable-bed modeling
is not as well established as hydrodynamic modeling,
Verification of the model is probably the single most
important aspect of conducting movable-bed modeling
studies.
Model verification should be the first task performed after the model has
been designed and constructed because the verification phase may alter how
the model is run. For example, sometimes morphological time scales differ
from the hydrodynamic time scale, and therefore, can only be determined
in the calibration or verification phase. In a few instances, such as twodimensional storm erosion on a beach profile17, verification of the modeling
criteria has already been accomplished in general, and the model results
can be taken as valid without additional specific verification.
Hudson, et al. (1979) listed the following as essential prototype data for
use in three-dimensional movable-bed model verification for coastal studies.
a. Detailed sediment-size distribution over the entire area of
interest
b. Computational estimates of yearly and monthly net longshore transport based on wave statistics, refraction, etc.
c. All available survey data
d. Accurate wave and sediment transport measurements
Of course, reality has its way of assuring that the available prototype
data will not be as complete as hoped, and so the engineer must make optimum use of what data are available. The requirement of reliable prototype
7 See Hughes and Fowler (1990b) for validation.