The purpose of this study is to clarify the relation between sediment transport from river and topographical changes of mouth-bar by field measurements in Tonda river, which is second grade river flowing in south of Wakayama prefecture. Upstream areas of Tonda river were damaged by slope failures due to heavy rainfall which was caused by Typhoon No. 12 in 2011, and a large amount of sediment was supplied into the river. In this study, we will conduct field observations using RTK-GNSS during the next few years in order to capture the transporting phenomena of the overabundant supplied sediment from upstream area to estuary and sea. In this paper, we reported our recent results of field measurements.