THE GROWTH OF FETCH LIMITED WAVES IN WATER OF FINITE DEPTH .3. DIRECTIONAL SPECTRA

The analysis of a comprehensive data set of fetch limited finite depth directional wave spectra is presented. The data show that the spectra are narrowest at the frequency of the spectral peak and gradually bro aden for frequencies both greater than and less than that of the peak. The directional spreading is found to be a function of f/f(p), where f is frequency and f(p) the frequency of the spectral peak. In additio n, the present data reveal consistently broader spreading than compara ble deep water data. Hence, it is concluded that finite depth effects lead to an increase in the directional spreading of the spectrum. An a nalysis of the nonlinear coupling of wavenumber components within the spectrum indicates that such effects may lead to enhanced directional spreading of spectra as the water depth decreases, consistent with the present data set.