Morphology, sedimentology and stratigraphy of Korean tidal flats – Implications for future coastal managements

• Korean tidal flats are morphologically classified into three types, open-coast, embayment, and channel margin.
• Korean tidal flats respond to dynamic interplay between tide, wave, river, and precipitation.
• Monsoon climate results in seasonal changes in morphology and sedimentology of tidal flats.
• Future reclamation project requires comprehensive study addressing natural complexity of tidal flat systems.

Tidal flats constitute a unique and extensive depositional system encompassing the entire west coast of Korea. Tidal flats are classified into three types on the basis of morphologic setting, open-coast, embayment, and channel-margin. Macrotidal regime and highly indented coastlines favored tidal current-induced sedimentation, resulting in seaward coarsening sediment distribution. Tide-dominated sedimentary processes are complicated by the strong monsoonal climate, and associated seasonal wave activity and precipitation-induced discharge. Different exposure to wave activity leads to contrasting sedimentary processes, sedimentation and morphologic response among various types of tidal flats. Summertime heavy rainfalls accentuate runoff discharge-driven sedimentation in the tidal flats, irrespective of the presence of rivers. Tidal flats have been venue for government-driven mega reclamation projects such as Saemankeum, Sihwa, and Youngjong–Yongyou islands due to their geographic proximity to urban area and flat morphology. Massive destruction of tidal flats was justified by mandatory environmental impact assessments that failed to predict irreversible effects on coastal depositional system, triggering a nationwide controversy. Future reclamation projects must be supplemented by studies that can evaluate properly the complexity and dynamic behavior of tidal flats so as to minimize socio-economic cost as well as the loss of tidal flats.