This study was performed to provide fundamental data for long-term geomorphic predictions of estuarine sandbars in the Nakdong River. We monitored the geomorphic changes of Jinudo (Jinu Island), which is located on the far-southern side of the first western sandbar. We evaluated the temporal and spatial dynamics of the sandbar and the relationship between erosion and deposit speed with environmental factors. We found that: 1) The south side of Jinudo showed very rapid water channel closing and shoal generation. This phenomenon was more obvious during autumn (September and October) than during spring, with greater water depth reduction and variation between sides. 2) The mean deposit speed for Jinudo was approximately 0.85 mm/day. The deposit speed was 1.32 and 1.26 mm/day for the east and south sides of Jinudo, respectively. The maximum deposit and erosion speeds were 27 mm/day and 26 mm/day in July and December, respectively, on the east side of the island. 3) Mean surface deposit size was 0.18-0.26 mm. The newly deposited sandbar had a rotatively larger deposit size than the original land. 4) Correlation analysis showed that, on the southern side of the island, deposit activity prevailed in the winter due to low precipitation and a northerly wind, while erosion was dominant in the summer due to high water flow and a southerly wind. In contrast, the correlation analysis for the eastern side of the island showed that deposition is dominant when water flow is high. These results indicate that geomorphic dynamics vary among island sides.