An investigation into the generation of waves when the fetch of the wind is less than 100 miles

Wave records taken at Lough Neagh by wave‐pressure recorders and waves recorded over the Irish Sea by an airborne wave recorder are used to investigate the variation of wave height and wave period with fetch and wind speed, when the fetch is below a hundred miles. For values of fetch below 1 mi, these observations are supplemented by measurements taken at Staines Reservoir. Empirical formulae are obtained for the maximum wave height, significant wave period, and spectral distribution of wave energy which reduce in the case of a large fetch to those already derived for waves in the open sea from weather ship observations. The formulae indicate that the steepness of the highest waves increases linearly with the wind speed and decreases with increasing fetch. An expression is obtained for the mean square slope as defined by Cox and Munk (1954) and, under certain conditions, agreement is found with their results.