Investigation of the mechanism of the generation of rip current and development of the procedure for predicting rip current using remote sencing.

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More than 100 lives were lost by accidents during swimming in the sea every year. It is reported that large part of the accidents were caused by the rip current. If we can predict the occurrence of rip current in advance, it is possible to reduce number of accident through the warning system. However, a certain kind of rip current suddenly. comes in to existence in a very narrow region and its lifetime is not so long. It is generally impossible to predict the occurrence of this kind of rip current. It is needless to say that this kind of rip current is extremely dangerous for swimmers.At the same time, rip current becomes transporting agency of bed material in the very shallow water region towards offshore.The aim of this study is to develop a rip current observation system by using local remote sensing from the balloon and to investigate the occurrence condition of rip currents. Surface displacement measuring system by stereo-camera images and bottom topography measuring system using K-GPS are also developed.Almost all patterns of orographic rip currents reported until now can be recorded in the field observations. Some of the measured flow patterns are reproduced by the numerical simulations of wave fields and wave induced current on the measured bottom topography by K-GPS. Measuring systems of mesoscale bottom topography and wave field are also developed and verified through the field observations.These results surely set up effective procedures for measuring wave fields and wave induced current in very shallow water regions.