Recovery process of sand spit at the natori river mouth

The Natori River, originates in Miyagi Prefecture, is one of the large and important river in Tohoku District in Japan. In 2002, a significant flood caused by typhoon 0206 with more than 230mm precipitation during two days induced remarkable flushing of the left sand spit at the Natori River mouth. The residential area near the river mouth has been damaged severely four times by flood within these 15 years. In order to protect the river mouth area, embankment has been constructed. After the completion of the construction, however, it is found that the sand spit recovery process has changed from that observed before the construction. In this study, the sand spit recovery process at the Natori River mouth is clarified thorough field measurements and photographs. It can be observed that the time scale of sand spit recovery process is dependent on the river scale. Moreover, it is seen that the sand spit tends to intrude seaward during beginning period after flood and tends to retreat riverward during the later period, as already observed by Uda and Matsuda (1995).