Wave downscaling strategies for practical wave agitation studies in harbours

Abstract

An accurate estimation of the historical harbour wave agitation is fundamental for many practical applications, such as port downtime analyses. In practical harbour agitation studies, usually based on numerical propagations from offshore wave climate towards a harbour (wave downscaling), the accuracy in defining the outer wave climate has an impact on wave agitation estimations, especially important for multimodal wave climates. In this paper, several strategies for wave agitation downscaling are presented based on different existing approaches with different accuracy levels for: a) wave downscaling method; b) definition of outer spectral waves. The accuracy/performance of each approach is evaluated by applying, and comparing them with multi-point instrumental data from a field campaign, in a real scenario (Africa basin, Las Palmas Port, Spain) where the multimodality of waves, in addition to the agitation effects from port structures in the far-field, clearly determines the final accuracy of the in-port wave agitation. Improved results have been achieved with the most sophisticated/accurate strategies proposed. A comparative analysis of the advantages, limitations, uncertainty and CPU effort of each one, allows to suggest the preferable strategy, in each situation/context, for practical port wave agitation studies. • Six different wave downscaling strategies for practical wave agitation studies in harbours are presented. • A strongly multimodal outer-harbour wave climate is analyzed, resulting in an important influence on in-port wave agitation. • An accurate real-shaped characterization of forcing spectral wave climate is achieved, through a dynamic wave downscaling. • An uncertainty reduction in wave agitation prediction, approximately by half, is obtained presenting an accuracy ranking. • Instrumental data-based uncertainty is quantified, and a comparative analysis suggests the best-strategy to be followed.