GEOLOGICAL AND GEOMORPHIC RESPONSES TO ESTUARINE DAM INSTALLATIONS AND LAND RECLAMATION WITHIN SOUTH KOREA: THE NAKDONG AND YEONGSAN ESTUARIES

초록

On the Korean Peninsula, significant anthropogenic alterations have occurred to drainage basins and estuaries due to river diversion, coastal construction of estuarine dams, and extensive seawalls in land reclamation projects. Over the past century these practices have modified the shoreline and altered both net transport of sediment and freshwater from these systems and modulated the timing and intensity of the discharge. As a result, sediment dynamics and ecosystems within the estuaries have been significantly altered. Considering drainage basins >500 km2, 56% of rivers reaching the coast in South Korea have been occluded by an estuarine dam, restricting delivery of sediments and altering/preventing natural tidal exchange of fresh and saltwater. The Nakdong and Yeongsan Estuaries are prime examples and are respectively representative of micro and macro-tidal estuaries found in the region. The impacts of the modifications include a substantial decrease in the tidal prism, reduction of accommodation space in intertidal zones, and changes in the dispersal mechanisms and accumulation of sediments. In order to assess these alterations, a geological and geophysical investigation was conducted. Our observations have found a shift in depositional environments and enhanced sediment-trapping efficiencies as a natural response to an extensive array of anthropogenic alterations, providing the basis for reevaluating traditional facies models for estuaries in the Anthropocene.