Beach changes due to the elongation of river mouth jetties around the mouth of the Kinoto-dainichi River in Niigata Prefecture was investigated. Topographic surveys were conducted five times from 1988 to 1997 and sea bottom changes were compared. Southward longshore sand transport prevails at this river mouth. After the extension of jetties south beach was gradually eroded, whereas sand accumulated at the river mouth. The function of an artifical reef being insta Iled off the mouth of the Kinoto-dainichi River to prevent sand deposition inside the river mouth was studied.
