Environmental investigations supporting site selection and providing design values have to consider the wave climate as one of the important factors. In most cases the available time does not allow for wind and wave measurements over the time span required to give reliable statistics. Alternative studies are thus necessary, utilizing the sparse amount of data collected in the vicinity of possible sites combined with long-term wind and wave statistics collected at some distance in deep water major efforts during recent years to develop models describing the energy redistribution as the wave approaches shallow waters have resulted in more and more sophisticated models. One of these is the shallow-water wave model HISWA. A brief description of HISWA is given, together with some practical information demonstrating how o use the model. HISWA has been extensively used to compute the wave conditions in the coastal areas of mid-Norway. Some selected cases are given to test the model, illustrating how to choose the input data. The experience so far is that the calculated results deviate within 10% of the measured significant wave height close to potential sites. The mean wave period is over-estimated in parts of the integration area. These encouraging results strongly suggest extensive use of the model combined with short-term wind and wave measurements, providing more reliable wave data for various purposes.

INTRODUCTION

Increased human activity both in the open sea and in coastal waters results in an increasing need for environmental data for design purpose. In this chapter we will concentrate on a method to provide shallow-water data. Wave data for shallow waters are needed for the construction and design of, e.g., harbours and terminals, and fish farms, and for studies of areas for pipeline landfall.

Due to the great number of physical processes influencing the wave conditions in shallow water, the various wave-measuring programs carried out along the Norwegian coast do not give sufficient wave data for the above-mentioned purposes. Some wave-measuring programs have been carried out in shallow waters too, but these data are normally valid within a very limited area. Hence only dedicated wave measurements or wave modelling can provide sufficient wave data for the various purpose mentioned. If wave measurements are chosen, these will have to continue for quite a while to give sufficient data coverage to give a satisfactory statistical estimate of design values.

Normally, there is not enough time or money available to carry out a sufficient wave-measurement program, especially during the early planning stages. Wave modelling therefore ranks as an interesting alternative. Using wave models, wave data both for planning and for design and construction purposes could easily be provided. In this way, the sparse amount of data collected in the vicinity of interesting areas combined with long-term wind and wave statistics collected at some distance in deep water can be combined.

OCEANOR has gathered encouraging experience using the HISWA numerical shallow-water wave model, and believe that the use of this model will support various planning and design need with necessary wave data in a most efficient way.

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