6.3. BEDLOAD-DOMINATED TRANSPORT MODELS
279
1. The movable-bed model suffered scale effects because of
nonsimilarity of the physical processes of sediment transport.
2. The movable-bed model was not adequately calibrated or
operated due to lack of necessary and sufficient prototype
data.
3. The prototype wave climate was oversimplified in the model.
4. Experimental errors and laboratory effects may have contributed to the model’s inaccuracies, but Jain felt any errors of this type were small relative to the similitude issue
(item 1 above).
Sill, Fisher, and Whiteside (1981) conducted a laboratory investigation
of ebb tidal shoals that form under the action of currents only. This experiment was a first step toward trying to understand the complex sediment
transport processes at tidal inlets. The model consisted of a steady ebb jet
discharging into a basin through an adjustable inlet throat section. Sand or
lightweight sediment was placed in the path of the jet and allowed to form
an equilibrium “horseshoe” shape. Sediment was placed either in mounds
directly in front of the jet or spread in an even layer before the jet; however, neither the placement nor the amount of sediment influenced the final
shape of the ebb shoal.
Latteux (1986) discussed experience gained from conducting movablebed sediment transport models at the Laboratoire National D’Hydraulique
in France. His paper focused on the difficulty is correctly representing
the sediment transport due to both short waves and currents. Incompatibilities between similitude requirements forces a compromise where either
the Froude wave height scale or Froude velocity scale must be distorted
so that the waves and currents each contribute the correct proportion to
the bottom shear stress. Which scale to distort becomes a judgment based
on the perceived relative importance of the waves and currents, with the
less important flow being the likely candidate for scale distortion. Latteux
also suggested that it may be appropriate to distort both scales in some
instances.
The modeling philosophy presented in Latteux’s paper was illustrated
by two example studies: Dunkirk outer harbor (N% = 400, Nz — 60) and
River Canche estuary. The purpose of the Dunkirk harbor model related
to shoreline changes resulting from longshore transport, and stability of
sand banks and channels outside the harbor entrance. Latteux described
the genesis of the model through several current scale modifications. The
River Canche study examined the impacts of damming the estuary as part
279
1. The movable-bed model suffered scale effects because of
nonsimilarity of the physical processes of sediment transport.
2. The movable-bed model was not adequately calibrated or
operated due to lack of necessary and sufficient prototype
data.
3. The prototype wave climate was oversimplified in the model.
4. Experimental errors and laboratory effects may have contributed to the model’s inaccuracies, but Jain felt any errors of this type were small relative to the similitude issue
(item 1 above).
Sill, Fisher, and Whiteside (1981) conducted a laboratory investigation
of ebb tidal shoals that form under the action of currents only. This experiment was a first step toward trying to understand the complex sediment
transport processes at tidal inlets. The model consisted of a steady ebb jet
discharging into a basin through an adjustable inlet throat section. Sand or
lightweight sediment was placed in the path of the jet and allowed to form
an equilibrium “horseshoe” shape. Sediment was placed either in mounds
directly in front of the jet or spread in an even layer before the jet; however, neither the placement nor the amount of sediment influenced the final
shape of the ebb shoal.
Latteux (1986) discussed experience gained from conducting movablebed sediment transport models at the Laboratoire National D’Hydraulique
in France. His paper focused on the difficulty is correctly representing
the sediment transport due to both short waves and currents. Incompatibilities between similitude requirements forces a compromise where either
the Froude wave height scale or Froude velocity scale must be distorted
so that the waves and currents each contribute the correct proportion to
the bottom shear stress. Which scale to distort becomes a judgment based
on the perceived relative importance of the waves and currents, with the
less important flow being the likely candidate for scale distortion. Latteux
also suggested that it may be appropriate to distort both scales in some
instances.
The modeling philosophy presented in Latteux’s paper was illustrated
by two example studies: Dunkirk outer harbor (N% = 400, Nz — 60) and
River Canche estuary. The purpose of the Dunkirk harbor model related
to shoreline changes resulting from longshore transport, and stability of
sand banks and channels outside the harbor entrance. Latteux described
the genesis of the model through several current scale modifications. The
River Canche study examined the impacts of damming the estuary as part