Simulation of Environmental Changes Consdering Sea-level Rise Near a Mega-scale Coastal Dike (Saemangeum [SMG] Dike, Korea)

Abstract

Yoo, S.-C. and Suh, S.-W., 2020. Simulation of environmental changes considering sea-level rise near a mega-scale coastal dike (Saemangeum [SMG] dike, Korea). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 309–314. Coconut Creek (Florida), ISSN 0749-0208.The construction of one of the biggest coastal dikes in Korea, the 33-km long Saemangeum (SMG) dike, was completed in 2006. Coastal environmental changes resulted in tidal asymmetry in the near field (i.e., adjacent to the dike) and the far field (i.e., up to opposite part of the Yellow Sea). Coastal hydrodynamic variations and engineering developments for gate operations (to maintain inner reservoir water quality (WQ) standards) rapidly alter coastal environments. The sea level is expected to rise by 80 cm by the end of this century, and an additional 21.4 cm of seasonal local summer sea level jump will serve as a reversing factor of WQ. This study applied the ADCIRC and EFDC models to simulate regional and local hydrodynamic and WQ changes. The far-field impacts of the SMG will occur continuously till year 2100 along the Chinese coast with M2 mordulation. The target water management level was set to elevation with respect to mean sea level (EL) as -1.5 m, which is very limited in terms of free discharge time for gate operation. According to the tidal excursion and residence time simulations, only 14% of gate operations in a month will be possible compared to the existing all-year-round condition, and only 4% will be exchangeable in summer. It is found that SMG yields alteration of tidal hydrodynamics showing overall de-amplification of ∼10 cm in the Yellow Sea (YS), especially along the west coast of Korea (WCK), as well as a slight amplification of ∼10 cm on the eastern coast of China. In addition, reducing the time for inner discharge because of the rising outer sea level directly influences WQ both in the areas near the gates and the inner water due to the increased residence time. Intensive study including long-term variations in tidal asymmetry and associated morphologies is needed to manage the hydrodynamic and/or WQ changes associated with such mega-scale coastal constructions.