Onshore portions of profiles are surveyed using standard land survey 

 techniques and equipment. Extending profile lines offshore beyond wading 

 depths requires a boat or amphibious vehicle. Positioning offshore can be 

 accurately and rapidly established by one of several high-precision navigation 

 systems now available. Fathometers can be used for continuous profiling of 

 the area seaward of the breaker zone but the signals are disrupted by breaking 

 waves in the zone. Further, boats suitable for offshore use cannot approach 

 close enough to the shore to connect direcdy to the land profile. Amphibious 

 vehicles are better suited to this task because they can traverse the sea-land 

 boundary and establish the continuity of profile lines. 



In waters relatively close to shore during favorable weather conditions, one 

 survey platform that is often used is a sea sled, consisting of a long upright 

 stadia rod mounted vertically on a base frame with sled-like runners 

 (Clausner, Birkemeier, and Clark 1986) or a mast with a prism for use by 

 total station survey techniques (Fredette et al. 1990). The sled is towed, 

 winched, or otherwise propelled along the profile lines (self-propelled, 

 remote-controlled sea sleds are currently being developed) while frequent 

 depth and position data are determined using onshore instruments. Because 

 neither the sea sled nor the onshore survey and positioning equipment are 

 floating, elevations are not subject to wave or tide variations, thus providing a 

 more accurate comparison between repeated surveys. At present, bottom 

 samples must be obtained from a boat or amphibious vehicle working in 

 conjunction with the sea sled. The technique is currently limited to use within 

 4 km of the coast and water depths of 12 m, less than the height of the sled 

 mast. 



Sedimentological and Stratigraphic Techniques 



In addition to examining large morphological features, examination of 

 small-scale morphology can provide much information on the variable nature 

 of coastal forms and processes. A number of techniques exist that enable 

 collection of data on present and past processes at a site, using information on 

 the characteristics of sediments and surface stratigraphy. 



Knowledge of sediment characteristics may be useful for predicting 

 sediment movement during storms, the nature of seafloor features, and the 

 geologic history of the area of investigation. Sediment transportation is 

 influenced by properties such as size, shape, and composition, with grain size 

 being most important. Differential transport of coarse and fine, angular and 

 rounded, and light and heavy grains leads to grading. There are several 

 samplers for determining the movement of sediments (McCave 1979; Seymour 

 1989). Sediment traps are a direct means of estimating sediment movement 

 (Kraus and Dean 1987). Bed surface sediments are typically collected widi 

 grab samplers and then analyzed using standard laboratory procedures as 

 described in other sources (Fredette et al. 1990; Buller and McManus 1979). 



Chapter 5 Investigation of Geomorphic Factors 



85 



