PIANC Smart Rivers 2022

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Abstract : *(250~1000 words)

Some ports located at the estuary or inner bays in Japan suffer from river-derived sediment. At a port located at the estuary, 800,000 m3/yr of sediment is accumulated annually in navigation channel and basin. In order to consider effective countermeasures, it is necessary to elucidate sediment dynamics due to waves and tidal currents of the target port. Therefore, we are conducting a field survey of sediment transport and deposition. In addition, we have developed a numerical simulation model based on the results of the field survey for evaluated the countermeasure. We introduce the knowledge about sediment transport obtained through multiple operations.

(1) Field Survey
We introduce basic and applied field survey methods. For the basic survey, bottom sounding using a single-beam or multi-beam will be conducted to reveal the actual situation. Characteristic areas can be identified through the results of this survey. For the application survey in the area, waves, currents, turbidity, etc. are investigated in order to elucidate suspended sediment transport and their deposition processes. We have knowledge of the optimal survey method through many survey results.

(2) Numerical Simulation
We have developed numerical simulation models of fine sediment transport for multiple ports in Japan. The feature of these models is taking account of fluid mud layer near the bottom. When necessary, it also take account of flocculation effects due to mixing process of river and sea water. In practice, customers demand speed and comprehensibility. Therefore, we focus on simply expressing the phenomenon in order to get quick and easy-to-understand results.

(3) Dredging and Sediment Disposal Plan
In the maintenance of navigation channels and basins, reducing dredging costs and creating disposal sites are issues to be resolved. In order to reduce the dredging cost, it is necessary not only to reduce the dredging amount but also to improve the work efficiency. One way to improve work efficiency is to dredge the pocket area outside the channel. In brief, the travel distance of the dredger can be shortened by concentrating the accumulated sediment in the pocket area. We evaluate the effects of pocket dredging and countermeasure facilities using a numerical simulation model, and draw up a long-term plan considering the probability of occurrence of meteorological disturbances such as typhoons.

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