Seasonal sedimentary processes of the macrotidal flat in Gomso Bay, Korea

Abstract

To understand seasonal sedimentary processes, we analyzed sediment grain size, short-term sedimentation rates, and chemical tracers to determine sediment provenance in the Gomso tidal flat, which is located on the western coast of Korea. It is a funnel-shaped embayment with a mean tidal range of 4.3 m. Calculating the elevation from a digital elevation model (DEM), the landward inner bay was relatively higher than that of the outer bay. Sandy sediments generally dominated the outer bay, whereas sandy mud sediments were distributed in the inner bay. The middle bay consisted of muddy sand sediments. From February 2011 to February 2012, the net deposition rate in the inner tidal flat of the bay was 41 mm/year. Erosion dominated the middle and outer tidal flats of the bay, with net erosion rates of -30 and -10 mm/year, respectively. Seasonal variations in sedimentation in the Gomso tidal flats occurred with deposition via the inflow of fine-grained sediments during spring and summer and winnowing from the bay during autumn and winter. The rare earth element (REE) analysis proved that the fine-grained sediments were transported from Jujin Stream in the southern bay and deposited on the middle bay tidal flats, especially during the rainy season. The source of the outer bay sediments was related to the inflow of fine sediments of alluvial origin. Therefore, the major forcing factors affecting the seasonal variation in sedimentation involve a combination of tidal currents and waves, together with heavy rainfall.