For acquiring undisturbed samples or samples at greater depths, some type of 

 coring device must be employed. 



Cores allow retrieval and examination of the subsurface material in the 

 area of investigation. From the recovered sediment sequence, much informa- 

 tion regarding history of the depositional environment and processes can be 

 determined. Depending upon the information required, the types of analyses 

 performed on the core may include grain size, sedimentary structures, the 

 occurrence of shells and minerals, organic content, microfaunal identification, 

 x-radiographs, age dating, and engineering tests. If it is important to under- 

 stand much about the geologic history of a site, vibratory corers will be 

 necessary, which may retrieve samples exceeding 12 m in length. Even 

 deeper cores can be recovered witli rotary drilling equipment. If only infor- 

 mation regarding recent processes is necessary, then a box corer, which 

 samples up to 0.6-m depths in the sediment and provides detailed information 

 regarding sedimentary structures, will likely be adeqate. 



Standard surveying techniques or large-scale aerial photographs are 

 preferable to side-scan sonar for acquiring bedform data on exposed sand 

 banks at low water. Dimensionless parameters of ripples and other bedforms 

 can indicate depositional environment (Tanner 1967). Flow directions can be 

 assessed in terms of the trace of the crestline (Allen 1968). Wave-formed 

 structures reflect the velocity and direction of the oscillatory currents, plus the 

 length of the horizontal component of orbital motion and the presence of 

 velocity asymmetry within the flow (Clifton and Dingier 1984). The flow 

 strength for inter-tidal estuarine bedforms can also be estimated for a given 

 flow depth by a velocity-depth sequence of bedform development (Boothroyd 

 1985). 



Heavy minerals may provide information regarding sources, processes, and 

 other aspects of geomorphic variability in the coastal zone. Pronounced sea- 

 sonal variations in heavy minerals may also occur in the beach and nearshore 

 samples, with foreshore samples showing higher concentrations in winter than 

 summer, and samples outside the surf zone showing lower concentrations in 

 winter than summer. An explanation for this phenomenon is that light 

 minerals are transported from the beach foreshore to deeper water during the 

 winter, and are transported back again during the summer (Inman 1953; 

 Nordstrom and Irmian 1975). 



Physical Models 



The use of physical models can also shed light on the geomorphic variabil- 

 ity of coasts. Physical models require scaling and calibration, and significant 

 time and expense to set up initially. Once in operation, however, they allow 

 for direct measurement of process elements, and the study and isolation of 

 variables that are difficult to assess in the field. Some examples of physical 



Chapter 5 Investigation of Geomorphic Factors 



