- SPECIAL PUBLICATION NO. 43
the negligible effect of sand-sized material on 1" .56 I w 1 runup for larger waves has been noted by ,.2s Savage (1958). His results strongly imply ., I- that relative to sand size, as the wave height *.7 T..s 5h. CA increases there is reached a point beyond os which sediment size within the sand-sized T i4
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range no longer discriminately responds. That is, the level of wave energy is overpowering even to the coarsest fraction o.3 of sediment available within the sand-size range. o.7
0.76
Hence, unless the wave climate is closely in equilibrium with sediment comprising the beach, one would not necessarily expect to find significantly T correlative seasonal changes in mean grain is size (or for that matter skewness, although 2 ..L it might be somewhat less sensitive to ., energy) within the sand-size range. The .. I. ll II 111 author located data where at least monthly J A JJ ASO. D J FMAUJ JASoND sand samples were collected with concurrent m m"
Fgure 10. Typical examples of time series relation wave data for sites along the U. S. west, of monthly data for breaker height, wave period, east, and Gulf coasts. There was no and foreshore slope grain size for California (data discernible seasonal correlation between from Ingle, 1966) and northwestern Florida waves and mean sediment grain size. panhandle (data from Balsillie, 1975) sites. Several typical examples are illustrated in Figure 10.
which may or may not differ from the Samsuddin (1989), however, reports characteristically rounded, quartzoseto have found correlation between seasonal feldspathic U. S. beach sands considered in changes in wave conditions, foreshore slope, this work. and sand-sized textural changes along the southwest Kerala coast of India, wherein There also occurs the case (CASE 2, mean grain size increased and kurtosis example 2) where a beach is comprised of decreased during higher seasonal wave sediments exceeding the sand-sized range. energy conditions (CASE 2, example 1). An example is Oceanside Beach, Oregon, Samsuddin's one-year investigation, in which mentioned earlier, in which all the sand-sized beach foreshore sand was seasonally summer beach material is removed to expose sampled, may have been a fortuitous year in a winter cobble beach. Under such which equilibrium conditions were more conditions, one would expect that sediment nearly manifest. Kerala sand samples are coarsening, as reflected by the mean grain also characterized by a consistently large size and skewness, would result from higher standard deviation which allows for greater wave energy levels because of the excessive leeway in sorting potential (0.6 to 0.7 phi size of coarser sediments. compared to 0.2 to 0.55 phi commonly found for U. S. beach sands). Unfortunately, When singularly considered, the 1st Samsuddin did not describe the mineralogy moment measure (mean grain size) tells us or shape characteristics of the samples nothing about the nature of the distribution.
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