FLORIDA GEOLOGICAL SURVEY
skewness and kurtosis are Table 3. Mean annual beach grain size (foreshore dimensionless. Otherwise, the slope samples) from monthly data, and range in size. granulometric moment measures can Annual Range be specified all in dimensionless phi Site D (mm) of D Source units. (mm) FLORIDA
Beach sands characteristically ..
h Bearang ians r mtl St. Andrews St. Pk. 0.29 0.04 Balsillie, 1975 have a range in size from 0.1 mm to Grayton Beach 0.37 0.13 Grayton Beach 0.37 0.13 .
1.0 mm (U. S. Army, 1984) which Crystal Beach 0.37 0.15 occupies about 46% of the sand- J. c. Beasley St. Pk. 0.40 0.11 sized range of Wentworth (1922; Navarre Beach 0.41 0.14 i.e., 0.0625 to 2.0 mm). From Table Fort Pickens Beach 0.43 0.27 3, it is apparent that the range in NORTH CAROLINA mean grain sizes occurring over an Duck 0.401 0.19 Miller, 1984 annual period is less than 1/3 of the .. commonly found range in beach sand GeP ac. 1 CA UFORNIA size (i.e., 0.9 mm). Therefore, the Goleta Pt. Beach 0.21 0.16 Ingle, 1966 Trancas Beach 0.22 0.18 typical annual mean grain size, D, for Santa Monica Beach 0.26 0.29 any beach might be an appropriate Huntington Beach 0.21 0.14 measure to consider as a property La Jolla Beach 0.17 0.04 element provided that sufficient
samples are available annually to Table 4. Two cases of sedimentologic obtain a reliable measure (e.g., a suite of response of moment measures to wave monthly samples). This implies that there enerY levels. needs to be a real difference in mean grain sizes from site-to-site for the application to CASE 1 CASE 2 have meaning. Even so, the use of mean Em Lae A ot EW Leive tAr twcesive fto flat Excessiv. to
grain size alone without consideration of s.anini s leenaogc standard deviation, skewness and kurtosis epos Rspons remains somewhat of a curiosity other than:
. MEAN GRAIN SIZE
1. its use results in a good fit for equation
(2), 2. is properly applied in equation (2) Ds DL DS > DL (i.e., the larger the value of D, the smaller SKEWNESS sKEWNESS
becomes Vs), 3. produces the proper unit dimensions for the equation, and 4. has sks SkL Sks < SkL been a considered variable in other research KURTOSIS
KURTOSIS
results.
Ks < KL KS < KL
It is generally the case (CASE 1 ofKS<LKs<L
It is generally the case (CASE 1 of NOTES: Subscripts S and L refer to the storm season Table 4) that the coarsest beach sand is and lull season, respectively. The corresponds to found in the swash zone, and which is the symbol, -, is meant to signify that the measure did only type of sample considered here since it not change due any recognizable response to energy directly represents energy expenditures of level force element changes. the littoral hydraulic environment. One might suspect that swash samples are coarser during the storm than the lull season. However, the range in sediment commensurate with bulk properties meeting size within the sand-sized range is limited for conservation of mass and energetics any beach to the coarsest available material constraints (Passega, 1957, 1964). In fact,
12