A ten-year data set for fetch- and depth-limited wave growth

This paper presents the key results from a ten-year data set for Lake IJssel and Lake Sloten in The Netherlands, containing information on wind, storm surges and waves, supplemented with SWAN 40.51 wave model results. The wind speeds U-10, effective fetches x and water depths d for the data set ranged from 0-24 m s(-1), 0.8-25 km and 1.2-6 m respectively. For locations with non-sloping bottoms, the range in non-dimensional fetch x* (=gxU(10)(-2)) was about 25-80,000, while the range in dimensionless depth d* (=g d U-10(-2)) was about 0.03-1.7. Land-water wind speed differences were much smaller than the roughness differences would suggest. Part of this seems due to thermal stability effects, which even play a role during near-gale force winds. For storm surges, a spectral response analysis showed that Lake IJssel has several resonant peaks at time scales of order I h. As for the waves, wave steepnesses and dimensionless wave heights H* (=gH(m0)U(10)(-2)) agreed reasonably well with parametric growth curves, although there is no single curve to which the present data fit best for all cases. For strongly depth-limited waves, the extreme values of d* (0.03) and H-m0/d (0.44) at the 1.7 m deep Lake Sloten were very close to the extremes found in Lake George, Australia. For the 5 m deep Lake IJssel, values of H-m0/d were higher than the depth-limited asymptotes of parametric wave growth curves. The wave model test cases of this study demonstrated that SWAN underestimates H-m0 for depth-limited waves and that spectral details (enhanced peak, secondary humps) were not well reproduced from H-m0/d=0.2-0.3 on. SWAN also underestimated the quick wave response (within 0.3-1 h) to sudden wind increases. For the remaining cases, the new [Van der Westhuysen, A.j., Zijlema, M., and Battjes, J.A., 2007. Nonlinear saturation-based whitecapping dissipation in SWAN for deep and shallow water, Coast. Eng., 54, 151-170] SWAN physics yielded better results than the standard physics of Komen, G.J., Hasselmann, S., Hasselmann, K., 1984. On the existence of a fully developed wind-sea spectrum. J. Phys. Oceanogr. 14, 1271-1285, except for persistent overestimations that were found for short fetches. The present data set contains many interesting cases for detailed model validation and for further studies into the evolution of wind waves in shallow lakes. (C) 2009 Elsevier B.V. All rights reserved.