Abstract
Field observation of the groundwater fluctuation has been conducting with the aim to obtain better understanding of groundwater dynamics in coastal sand-dune environment. Ogata beach in Joetsu coast was selected as field observation location. The Ogata sand dune (20km in length, the maximum of 1km in width, the maximum height of 30m) which is the layered structure of new and old dunes is distributed along the margin of Takada plain. The field observations and analysis of the tide and beach groundwater changes for particular points along beach profile, revealed interesting characteristics, include: strong correlation between tidal and beach groundwater fluctuation and so on. As a results, fresh groundwater supply in terms of steady flow theory is estimated to amount from 13.3 to 79.9m3/day per meter of beach width.
