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# 2.3 Waves and winds

A critical factor in the design of structures which interact with the sea is the likely worst-case wave height, which is known as a design wave. It is considered that even this might be exceeded once every 50 years. In the absence of any real wave height records, the 50-year design wave may be predicted using records of severe wind and weather conditions for the area of concern. The more frequent smaller waves that might over time have an effect on the fatigue life of structures must also be considered. Figure 15 shows a historical map for the waters surrounding the UK for the late 1970s; the kind of map that would have been consulted in the design of offshore oil rigs. This was based on maps from the Institute of Oceanographic Sciences.

Figure 15 50-year wave heights (in metres) around the UK

Winds, of course, have a direct effect on the size and speed of waves beyond causing swells a long distance away. Table 2 related the Beaufort scale of wind speeds to the direct effect on the oceans and seas. Conversely, the state of the seas is one way of estimating the Beaufort wind rating.

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