서해안의 새 방파제 건설에 따른 연안 퇴적환경의 변화

Abstract

Recently a new seawall, a total length of 3.1 km, was constructed from 2011 to 2016 at 4 km offshore from sector II of the Saemangeum tide dike built during the period of 1992 to 2006 located the west coast of Korea. The 45-cm-long gravity core (GC54) was collected from near the new seawall in order to find out changes in the coastal depositional condition by an artificial structure. A precise grain-size analysis was conducted with samples subsampled at a 1-cm interval from the core using a laser diffraction particle-size analyzer. As results, vertical grain-size distributions (GSD) of the whole core showed a fining-upward trend (Figure 1). More detailed GSD patterns were revealed by the partitioning of components population (PCP) analysis. The lower part of the core between 12-45 cm showed distinct bimodal patterns with primary and secondary modes in very-fine sand (4 phi) and finer-grain components (6 phi - 8 phi), respectively. The upper part of the core, on the other hand, had a unimodal pattern predominantly consisting of muddy sediments that are finer than 6 phi. The finer component in the upper part was interpreted as new-born materials that have been deposited since the new seawall construction. Study site’s depositional environment turned into the low-energy condition allowing mass accumulation of fine sediments due to the new seawall that weaken tidal and wave activities. More careful attentions should be core (GC54) was collected from near the new seawall in order to find out changes in the coastal depositional condition by an artificial structure. A precise grain-size analysis was conducted with samples subsampled at a 1-cm interval from the core using a laser diffraction particle-size analyzer. As results, vertical grain-size distributions (GSD) of the whole core showed a fining-upward trend (Figure 1). More detailed GSD patterns were revealed by the partitioning of components population (PCP) analysis. The lower part of the core between 12-45 cm showed distinct bimodal patterns with primary and secondary modes in very-fine sand (4 phi) and finer-grain components (6 phi - 8 phi), respectively. The upper part of the core, on the other hand, had a unimodal pattern predominantly consisting of muddy sediments that are finer than 6 phi. The finer component in the upper part was interpreted as new-born materials that have been deposited since the new seawall construction. Study site’s depositional environment turned into the low-energy condition allowing mass accumulation of fine sediments due to the new seawall that weaken tidal and wave activities. More careful attentions should be