Discussion on Papers 8–13

MR WOLFE-BARRY, Paper 8 Although deep-water waves are reasonably well documented around the British Isles, there is rarely direct information available for a particular near-shore location or time to collect statistically meaningful data. Valuable data could often be obtained if clients were to initiate site investigations as soon as a project is identified, rather than waiting perhaps several years until the designer is appointed, but this is seldom done. It is therefore usually necessary, within the time span of the design stage, to use refraction and other techniques to transfer the deep-water wave spectrum

to the near-shore site.

Figure 1 shows a typical forward-tracking ray diagram. It gives qualitative information of wave concentrations and shadows for a particular deep-water wave direction and frequency. The technique breaks down when the bathmetry is irregular, as in Fig. 2, which is meaningless. It is therefore normal practice to use backtracking techniques (Fig. 3) whereby wave rays are traced backwards from the point under study into deep water. The denser concentrations of the rays in the fan indicate the deep-water wave directions that are of particular importance.