94
R.H. Chartier and Chr. P. De Meyer
Kana (1979) observed the following phenomena"
• concentration profiles have a similar shape in spilling and plunging breaking
waves,
• concentrations are a factor 5 larger in case of plunging breaking waves.
Kroon and Van Rijn (1988) observed the following phenomena :
• the near-bed concentrations are of the same order of magnitude (factor 2) as
those of Kana (1979), Steetzel (1987) and Van Rijn (1987) for spilling
breaking waves,
• the concentrations at mid depth and near the surface are smaller than those of
Kana (1979) but comparable (factor 2) to those measured by Van Rijn (1987)
in the large wave flume at similar wave heights.
Based on the available measurements, the following concentration ranges can be
given for the surfzone with bed material in the range of 200 to 300 #m and water
depths of I to 2 m :
sediment concentrations
near-bed concentrations
near surface concentrations
I
spilling breakers
0.5 - 1.5 kg/m 3
(0.031 - 0.092 lb./ft. 3)
0.05 - 0.2 kg/m 3
(0.003 - 0.124 lb./it. 3)
plunging breakers
1 - 5 kg/m 3
(0.062 - 0.31 lb./ft. 3)
0.5 - 1.5 kg/n¢
(0.031 - 0.092 lb./ft.')
The data indicate that the breaker type is a dominating factor in waverelated
sediment suspensions. Spilling breakers are less effective than plunging breakers,
which is probably caused by the relatively small scale of the eddies generated by
spilling breakers. Furthermore, these small eddies are confined to the near-water
surface region and do not extend below the trough level (Miller, 1976). Plunging
breakers show strong jets penetrating to the seabed resulting in the generation of
large sediment concentrations.
R.H. Chartier and Chr. P. De Meyer
Kana (1979) observed the following phenomena"
• concentration profiles have a similar shape in spilling and plunging breaking
waves,
• concentrations are a factor 5 larger in case of plunging breaking waves.
Kroon and Van Rijn (1988) observed the following phenomena :
• the near-bed concentrations are of the same order of magnitude (factor 2) as
those of Kana (1979), Steetzel (1987) and Van Rijn (1987) for spilling
breaking waves,
• the concentrations at mid depth and near the surface are smaller than those of
Kana (1979) but comparable (factor 2) to those measured by Van Rijn (1987)
in the large wave flume at similar wave heights.
Based on the available measurements, the following concentration ranges can be
given for the surfzone with bed material in the range of 200 to 300 #m and water
depths of I to 2 m :
sediment concentrations
near-bed concentrations
near surface concentrations
I
spilling breakers
0.5 - 1.5 kg/m 3
(0.031 - 0.092 lb./ft. 3)
0.05 - 0.2 kg/m 3
(0.003 - 0.124 lb./it. 3)
plunging breakers
1 - 5 kg/m 3
(0.062 - 0.31 lb./ft. 3)
0.5 - 1.5 kg/n¢
(0.031 - 0.092 lb./ft.')
The data indicate that the breaker type is a dominating factor in waverelated
sediment suspensions. Spilling breakers are less effective than plunging breakers,
which is probably caused by the relatively small scale of the eddies generated by
spilling breakers. Furthermore, these small eddies are confined to the near-water
surface region and do not extend below the trough level (Miller, 1976). Plunging
breakers show strong jets penetrating to the seabed resulting in the generation of
large sediment concentrations.