Infiltration Flow Through a Sand Spit at the Nanakita River Mouth

Abstract

Development of a sand spit can frequently be observed at river mouths where sediment transport by wave action is more predominant as compared with flushing ability by tidal and river discharge. Progress of river mouth closure may cause reduction in flow through a river opening, resulting in increase in infiltration flow through a sand spit at a river entrance due to distinct water level difference between inside and outside of a river mouth. However, there have been quite few investigation on this type of flow, although there have been many on coastal aquifer in connection with salinity intrusion and beach stabilization by dewatering of coastal aquifer. In the present study, results of field observation of infiltration flow in a sand spit at the mouth of Nanakita River are described. Comprehensive numerical simulation is also performed to investigate the effect of water level variation in the mouth on the strength of infiltration flow.