Manomay Shravage

Five factors affect the growth of wind waves. First, the wind speed must be blowing faster than the transfer of energy from wave crest to wave crest.  The second factor is the amount of time the wind blows, or wind duration.  The third factor is the fetch, the uninterrupted distance over the sea for which the wind blows without a change in direction. In the Solent, for instance, the fetch is limited by the surrounding coast of the mainland and the Isle of Wight and is rarely more than 10 miles. At sea it can be thousands of miles.

As waves enter shallow water their speed decreases, wavelength decreases, and height increases.  Waves therefore tend to break in shallow water, for example over a bar at the entrance to a harbour. If the tide direction is against the wind, this will also increase wave height and decrease wavelength. Shallow estuaries and harbours such as Salcombe, Chichester and Carteret will experience large waves in an strong onshore wind, particularly with a Spring ebb tide, and must be avoided in such winds.So in total, wave height is affected by:

  1. Wind speed
  2. Wind duration
  3. Fetch - distance of wind travel over open water
  4. Depth of water / roughness of sea bed
  5. Direction and speed of tide