Waves, which are the main source of ship motions in a seaway, considerably affect the performance of a ship. The study of waves and their impact on ship motions within harbors is an important aspect of the design and operation of harbors. The prediction of incoming groups of waves is particularly important for evaluating ship motion within a harbor. Such a prediction makes it possible to evaluate ship safety more accurately. The wave transformation model reported here is applied to actual ports based on Boussinesq wave equations both non-linear and dispersive wave processes be considered in order to capture physical effects such as wave shoaling, refractions, reflection and diffraction in variable depth environments. The prediction of incoming groups of waves is particularly important for evaluating ship motion within a harbor, Such a prediction makes it possible to evaluate ship safety more accurately and provide safe wave informations for navigation. Furthermore, a wave information support system is proposed for entering ships as one technique for improving the safety of ship operations. This system predicts the run of waves and reduces the danger by identifying the most dangerous point near the harbor entrance at the small wave groups.

Maritime transportation consists of various situations such as navigation in the ocean, ship handling at harbor entrances, cargo handling and mooring in harbors. Generally, ships are built for the purpose of currying people and materials upon the seas. In order to accomplish the mission, a ship must be built to withstand the rigors of heavy weather and waves. In particular, the safety of ship motions at the entering/departing harbor and mooring under the effects of waves is very important for ship operation from the viewpoint of marine engineering. Therefore, safety and efficiency during entrance, departure, and mooring are extremely important aspects in the evaluation of ship operations from viewpoints of ship motions. However, the ship motions near a harbor entrance are not observed or studied as much. In this paper, to evaluate the difficulty of ship operations, field observations were performed using a new observation system with high accuracy in typhoon seasons, and grasp was done concerning about the time series characteristic that ship motions change rapidly within a harbor. Namely, such observations enable the quantitative safety evaluation under the effects of waves during ships entering and departing harbors in heavy weather.