274
CHAPTER 6. SEDIMENT TRANSPORT MODELS
three different median grain sizes, and six different wave conditions. The
models were scaled according to the Sand Model, and they were undistorted
so that wave refraction and diffraction would be in similitude. Scale effects
were expected from dissimilarity of the relative length parameter. Their
scale series indicated that volume of erosion was primarily a function of
the geometric link between wave motion and particle size (H/d), and the
scale effect varied with time and was found to be a function of model length
scale. Their study perhaps illustrated the “art” in state-of-the-art.
Dean (1985) pointed out that results from past longshore sediment
transport Sand Models gave transport rates that are low relative to prototype transport rates, and this was explained by the fact that the model
sediment represents very coarse sediment when scaled to prototype via the
model length scale. In other words, the model grain size was large compared to the mobilizing forces, and the resulting transport in the model was
primarily via bedload transport.
Dean examined past field and laboratory longshore transport results to
demonstrate that scaling of the sediment fall speed gives a better correspondence between prototype and model. This seems logical based on the
premise that the majority of longshore transport takes place in the surf zone
where wave-breaking turbulence mobilizes the sediment, and a significant
portion of the transport takes place as suspended load.
Kamphuis (1985) discussed some aspects of conducting movable-bed
models of longshore transport on a straight beach, and he cited as an example an earlier study of such a model by Kamphuis and Readshaw (1978)
. More recently, Kamphuis (1991a) reported on a comprehensive study of
longshore sediment transport using regular waves (7 tests) and irregular
waves (21 tests). Two sizes of model sand (d5o = 0.105 mm and 0.18 mm)
were tested to determine whether grain size was an important parameter.
Tests consisted of wave action from a constant direction for a total of 7 onehour periods. Longshore moving sand was trapped at the downdrift end,
and an equivalent amount of sand was introduced at the updrift model
boundary. Many of the details and difficulties associated with operating a
movable-bed model of longshore transport are described in his paper.
Kamphuis (1991a) plotted results from one of the experiments that indicated the total longshore sediment transport was divided almost equally
between bedload and suspended load, thus complicating formal scaling analyses. The model total transport rate calculated from the trapped sediment
was compared to similar prototype transport rate estimates, and Kamphuis
was able to show that both model and prototype results could be well described by an equation given as
CHAPTER 6. SEDIMENT TRANSPORT MODELS
three different median grain sizes, and six different wave conditions. The
models were scaled according to the Sand Model, and they were undistorted
so that wave refraction and diffraction would be in similitude. Scale effects
were expected from dissimilarity of the relative length parameter. Their
scale series indicated that volume of erosion was primarily a function of
the geometric link between wave motion and particle size (H/d), and the
scale effect varied with time and was found to be a function of model length
scale. Their study perhaps illustrated the “art” in state-of-the-art.
Dean (1985) pointed out that results from past longshore sediment
transport Sand Models gave transport rates that are low relative to prototype transport rates, and this was explained by the fact that the model
sediment represents very coarse sediment when scaled to prototype via the
model length scale. In other words, the model grain size was large compared to the mobilizing forces, and the resulting transport in the model was
primarily via bedload transport.
Dean examined past field and laboratory longshore transport results to
demonstrate that scaling of the sediment fall speed gives a better correspondence between prototype and model. This seems logical based on the
premise that the majority of longshore transport takes place in the surf zone
where wave-breaking turbulence mobilizes the sediment, and a significant
portion of the transport takes place as suspended load.
Kamphuis (1985) discussed some aspects of conducting movable-bed
models of longshore transport on a straight beach, and he cited as an example an earlier study of such a model by Kamphuis and Readshaw (1978)
. More recently, Kamphuis (1991a) reported on a comprehensive study of
longshore sediment transport using regular waves (7 tests) and irregular
waves (21 tests). Two sizes of model sand (d5o = 0.105 mm and 0.18 mm)
were tested to determine whether grain size was an important parameter.
Tests consisted of wave action from a constant direction for a total of 7 onehour periods. Longshore moving sand was trapped at the downdrift end,
and an equivalent amount of sand was introduced at the updrift model
boundary. Many of the details and difficulties associated with operating a
movable-bed model of longshore transport are described in his paper.
Kamphuis (1991a) plotted results from one of the experiments that indicated the total longshore sediment transport was divided almost equally
between bedload and suspended load, thus complicating formal scaling analyses. The model total transport rate calculated from the trapped sediment
was compared to similar prototype transport rate estimates, and Kamphuis
was able to show that both model and prototype results could be well described by an equation given as