8. Various instruments and apparatus have been developed to allow 

 measurement of transport rates over intervals on the order of seconds, 

 minutes, and hours. It is relatively easy to measure wave and current 

 conditions occurring during such an interval, as opposed to long-term, 

 spatially integrated deployments. Apparatus that have been developed for use 

 in the near shore zone include those that collect an instantaneous bulk water - 

 sediment sample (e.g., Kana 1976, 1977; Zampol and Waldorf in press; Inman 

 1978); time -integrating samplers that pump or siphon sediment- laden water 

 (e.g., Watts 1953, Thornton 1972, Fairchild 1972, Thornton and Morris 1977); 

 pit samplers that collect material moving into an excavated region of the bed 

 (e.g., Inman and Bowen 1963, Anderson 1987); and direct-measuring traps that 

 retain sediment moving into some collection area (e.g., Inman 1949, James and 

 Brenninkmeyer 1971, Lee 1975, Pickrill 1986, Kraus 1987). Indirect-measure- 

 ment instruments measure some phenomena occurring over a fixed distance as a 

 result of sediment transport, such as the attenuation of light (Hom-ma, 

 Horikawa, and Kashima 1965; Thornton and Morris 1977; Brenninkmeyer 1973, 

 1974), intensity of backscattered light (Jaffe, Sternberg, and Sallenger 1984, 

 Hanes and Huntley 1986, Downing 1984, Beach and Sternberg 1987), absorption of 

 nuclear radiation (Basinski and Lewandowski 1974), or absorption or back- 

 scatter of sound (Tamura and Hanes 1986, Hanes and Vincent 1987). 



9. An apparatus such as a direct-measurement trap allows a representa- 

 tive sample of the moving sediment to be collected and retained for further 

 analysis. Traps are also economical to construct and maintain, and the data 

 analysis procedure requires no specialized software or electronic expertise. 

 On the other hand, such an apparatus does have disadvantages. Sediment traps 

 present an obstruction to the wave and current fields; therefore, transport 

 may be significantly altered in the vicinity of the device. Traps can cause 

 scour near the bed, thereby creating an artificial transport rate. However, 

 if these limitations can be overcome, traps are well-suited for obtaining 

 short-term measurements of sand transport as a function of the existing 

 environmental conditions. Very few apparatus or instruments have been 

 developed to measure sand transport both at the bed and throughout the water 

 column. Data collected with sand traps can be used to supplement, verify, and 

 improve other, perhaps longer-term, measurement methods discussed above. 



