Simulating Long-Term Morphological Changes in the Nakdong River Estuary: Evaluating the Effects of Restoration Initiatives

The Nakdong River Estuary (NRE) in Korea has undergone significant anthropogenic alterations, including the construction of two estuarine dams and the reclamation of approximately 17 km² of tidal flats. These modifications have shifted the depositional environments from tidal-dominated to wave-dominated, leading to the formation of barrier islands from sand shoals at the estuary entrance (Williams et al., 2013, Marine Geology). Recently, the Korean government has initiated a controlled restoration project at the NRE. This study aims to assess the long-term effects of restoration on morphological changes in the estuary. We conducted simulations using a calibrated COAWST modeling system over a decade, assuming the absence of estuarine dams and land reclamation (Chang et al., 2020, Marine Geology). Surprisingly, our simulations revealed the re-establishment of the ebb-tidal delta where barrier islands formed after the dam construction. Additionally, the sediment texture underwent a notable shift from mud-dominated to sand-dominated, attributed to increased current velocities within the estuary. These sedimentary changes exhibited a longer time-scale, while the hydrodynamic changes from a wave-dominated to tide-dominated system had immediate effects. These findings carry significant implications for resource managers, especially amidst the growing demand for estuarine restoration. The study underscores the complex interplay between anthropogenic interventions and natural processes in estuarine environments, emphasizing the importance of long-term monitoring and adaptive management strategies for successful restoration initiatives.