Research on Development of the Rip Current Measuring System by using Acoustic Tomography

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Every year, more than 300 swimming people lose their lives in beaches. These casualties are mainly caused by the rip current flowing to offshore. For the continuous observation of the rip current, The aim of this research is to develop the real-time monitoring system of the rip current by using the acoustic tomography.The system consists of one dual-frequency acoustic fish-finder, two broad-band acoustic transducers, a set of sound reflectors and a data acquisition network. The modified dual-frequency acoustic fish-finder alternatively transmit and receive the sound signals of 50kHz at a few seconds interval. The observations were carried out in the Uradome Beach of Tottori Prefecture in September of 2012 and 2013. Based on these observational data, the current velocity fields were well reconstructed and weak offshore currents were detected. In conclusion, it was proved that the developed measurement system have a potential capability of monitoring the rip current.