Computer Prediction of Wave Heights in Coastal Areas

ABSTRACT Virtually all engineering work along the coast and offshore must consider wave forces, and this consideration requires the knowledge of wave heights, wave periods and wave directions. Unfortunately there are very few coastal areas of the world for which adequate wave data is available, although wave data for deep-water waves further off the coast is usually available. The task of predicting wave conditions in Shallow water based on deep-water wave information using traditional techniques is very tedious and time-consuming. The methods usually consider the effects of shoaling, refraction and diffraction separately. A computer program was developed which considers all these effects and predicts the changes in the direction and height of water waves. A hypothetical case of a harbor protected by a breakwater was selected as an example for computer calculation. The computer solution was verified experimentally in a three-dimensional wave basin. The agreement between the computer solution and experimental results are considered good. Applications of the computer program to design and analysis are also discussed. INTRODUCTION Engineering in the oceans today is largely concentrated in shallow waters where water waves are influenced by the ocean floor and other obstacles. In some coastal regions these factors that change the nature of water waves all work together to increase the incoming wave height, while in other regions the wave height may be decreased or the wave direction changed. The problem of determining precisely what changes will occur in a wave form in coastal waters is of great importance to the engineer. Wave forces must be considered in the design of almost any offshore facility. Drilling platforms, anchor systems and pipelines are but a few of the examples of structures that might come under the force of waves. The force of a wave may be evaluated provided the wave period, height and direction are known, yet accurate information on the wave period, height and direction for any particular location is very difficult to obtain. Such information may be in the form of a chart of offshore wave heights and directions, or a "wave rose" for deep water, or may consist of only the weather hindcasts from which the deep-water wave conditions can be estimated. In any case, none of this information is sufficient for the design purposes unless some means are available to predict wave transformation from deep water to shallow water at any particular point of interest. The purpose of this paper is to describe a means of predicting the change of wave form in coastal waters with the aid of the digital computer.