The contour-line-change model considering change in grain size given by Kumada et al.(2005) was applied to the Enshu-nada coast, where beach erosion has taken place due to the effect of decrease in fluvial sand supply from the Tenryu River. Bottom sampling was carried out in an extensive area of the coast. Depth distribution in median diameter and longitudinal profiles were measured. The grain size was divided into three dominant grain size populations such as fine sand, medium sand and gravel. The effect of beach nourishment using materials of different grain sizes was predicted. Optimum beach nourishment is the nourishment using coarse materials in a zone, where beach erosion is severe and protected by detached breakwaters, and simultaneously, beach nourishment using fine sand on downcoast.