On the 2D modelling aspects of wind-induced waves in shallow, fetch-limited lakes

Abstract

Wind-induced waves play an important role in shallow lake hydro- and sediment dynamics. But most of the field measurement methods can give information about the wave properties only at single point, which calls for wave estimation methods to take the effect of waves into account in multidimensional hydro- and sediment dynamic models. The aim of this study is to improve modelling waves in depth- and fetch-limited lakes generated by the local winds. In the first part of this paper, we describe the calibration and validation of the 2D spectral wave model SWAN (Simulating Waves Nearshore) to the very shallow Lake Neusiedl, Hungary/Austria. The abrupt change of the roughness at the perimeter of the open lake and the gradual change along the fetch due to wave growth result in a systematic, fetch-dependent variation of the wind speed. This spatial inhomogeneity is modelled here by a 1D atmospheric internal boundary layer (IBL) model. It is shown in the second part of this paper that this approach results in a significant effect on wave parameters and, as a consequence, on bottom shear stress.