Field research on hydraulic problems concerning coasts and harbors facing oceans and development of data sharing system

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During the research period, we carried out wave observations three times for the periods of Sep.7, '96 - Oct.19, '96, Sept.10, '97 - Oct.30'97 and Sept.5'98 - Oct.1'98 on the Pacific coast off Akabane harbor using two wave and current meters. We obtained high wave records provided by several typoons passing near the harbor. We also carred out wave and current measurements in the harbor when some of the typhoon became close to the harbor.On the basis of the wave data, we investigated the characteristics of offshore waves and oscillation in the harbor, where we especially focused on long period waves and studied its amplification and propagation properties. We also developed FEM model to simulate forced oscillation in the harbor, by which we studied oscillation characteristics comparing numerical and observed results. The main results are as follows : (1) The magnitudes of long period waves increase as wave heights increase. The amplitude of long period waves is almost proportional to the product of significant wave height and wave period. (2) Long period waves in offshore zone are comprised of on-offshore components and longshore components at similar degree of magnitudes. By analyzing cross correlations of wave records between two measuring points, we can distinguish incident and reflected waves in each component waves. (3) In Akabane harbor, there exist multiple frequency responses with 100S, 300s and 800s. The numerical simulation, where linear response to linear long waves is assumed, does not give sufficient agreemet with observations.We developed WWW server to give the service of wave data sharing, where all the wave data are open to public on the internet. In addition to wave data, the data of wind, atomospheric pressure distribution and typhoon trajectories are also involved. About several hundreds times of access to the database have been counted.