The right side of equation (4) is the manner in which the sand transport 

 relationship is presented in the SPM, where K* is assumed constant and has 

 dimensional units. 



Available field data indicate that none of the approximately 56 data points 

 are based on both measured wave direction and volumetric accumulations in a 

 total trap. Some are based on visually observed wave directions at a location 

 quite distant from the measured wave heights. In addition, much of the sedi- 

 ment data are based on tracer studies with the attendant uncertainties in 

 estimating depth of effective motion. 



The following brief review of field data on sand transport relationships, 

 used in the SPM and other studies (see Galvin and Schweppe, 1980), is helpful 

 in assessing the currently used relationship. Laboratory data have been 

 omitted as they do not represent a properly scaled version of the prototype, 

 since the scaled sediment size is significantly larger than is usually present 

 with sand-sized particles. The review is presented in chronological order of 

 the various investigations which yielded the data. Other reviews include Das 

 (1971) Greer and Madsen (1978), and Bruno, Dean, and Gable (1980). 



a. South Lake Worth Inlet, Florida (Watts, 1953) . Longshore transport 

 rates were based on quantities of sand transferred by a permanent sand by- 

 passing plant on the north jetty of South Lake Worth Inlet. The pressure drop 

 of the bypassing pump was correlated with sand discharge by a series of pumping 

 events into a diked disposal area on the downdrift (south) side of the inlet 

 and subsequent surveys of the associated volumes. Thereafter, transport rates 

 were inferred from the (calibrated) pressure drop of the pump. Wave charac- 

 teristics were based on (1) wave height measurements from a staff gage mounted 

 on the South Lake Worth pier about 16 kilometers north of the inlet, and (2) 

 visual observations of wave direction at the surfline as obtained from a van- 

 tage point about 6 kilometers north of the inlet. This study yielded four 

 data points with a sediment diameter of approximately 0.4 millimeter. The 

 average K value is 0.90 with a standard deviation of 0.11. 



b. Anaheim Bay, California (Caldwell, 1956) . Dredged material from the 

 entrance to Anaheim Bay was placed on the downdrift (southeast) shore, and 

 repeated surveys of this area were conducted as the material was transported 

 in a southerly direction. Changes in volume were interpreted as longshore 

 transport rates and estimates of longshore component of wave energy flux were 

 based on (a) wave staff measurements from the Huntington Beach pier about 9 

 kilometers to the south, and (b) wave directions based on hindcasts and recog- 

 nition of the sheltering by the offshore islands for waves originating from 

 certain directions. This study provided five data points with a sediment diam- 

 eter of approximately 0.40 millimeter. The average K value is 0.76 with a 

 standard deviation 0.38. 



c. Cape Thompson, Alaska (Moore and Cole, 1960) . The growth of a spit 

 and associated waves were observed over a 3-hour period. Spit volumes were 

 measured by plane table survey, and wave characteristics were based on visual 

 estimates. Only one data point was obtained with a K value of 0.25 for a 

 sediment diameter of 1.00 millimeter. 



d. Silver Strand, California, and El Moreno, Baja California (Komar and 

 Inman, 1970) . These data represent transport over fairly short-time intervals 

 as determined from sand tracer measurements and wave energy fluxes derived 



14 



