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| | Abstract | | Water covered areas such as river streams, dam reservoirs, and harbors have been left behind as the blank areas for near surface geophysics, in contrast to inland lakes and the shallow offshore areas, mainly due to its large cost-benefit ratio, or expensive costs as for the public works. Underwater parts of earthen structures, which bound town side with water side safely, have been left behind too. Recent severe geohazards stricken Japan remind us the importance of safety assessment of underwater parts of earthen structures along with land parts of them. Integrated geophysical investigations have been requested to be applied to the underwater parts of earthen structures. The authors have proposed an integrated geophysics for the safety assessment of levee systems, and developed Hybrid Surface Wave Survey (HSWS) method as the major component of it. Thus, we conducted needs analysis on underwater survey of earthen structures and carried out a preliminary study of integrated geophysics in a river channel which was seasonally submerged. As a result, we could successfully obtain near surface S-wave velocity and resistivity structures through 50 cm to 2 m deep river water. |
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