Waves, currents and morphological changes on a barred beach were investigated on the basis of numerical simulations and field data obtained at Hazaki Oceanographical Research Station (HORS), which is a research facility for field measurements in the nearshore zone and has a 427-m-long pier.
　The beach profile data obtained for eight years showed that a bar crest at Hasaki repeatedly migrated seaward with a period of a year, whereas the cross-shore sediment transport associated with the medium-term bar crest migration fluctuated seaward and shoreward. Seaward sediment transport occurred on and around a bar crest and shoreward sediment transport occurred in a trough region. The temporal variation of the magnitude of the cross-shore sediment transport rate corresponded to the offshore wave energy.
　Field measurements of wave height and mode of wave breaking, breaking or non-breaking, showed that the mean value of the wave height-water depth ratio at wave reforming in the field was 0.35. A wave transformation model including the criterion on wave reforming agreed well with field measurements.
　The cross-shore distribution of the time-averaged longshore current velocity on a barred beach was then discussed on the basis of fifty-two distributions. The result is that eighty-five percent of the distributions had peak velocities shoreward of the bar crests, which were not reproduced by previously proposed models. Hence, a one-dimensional model for nearshore current including the surface roller effect, which was neglected in previously proposed models, was developed and compared with longshore current velocities measured at HORS. The distributions of the longshore current velocity predicted with the present model had peaks shoreward of the bar crests and fitted those in the field.