Hydraulic and Environmental Stability Analysis in the Estuary of Gahwa River and Sacheon Bay by the Change of Discharge of Namgang Dam in South Korea

Abstract

Namgang darn is located in the southern part of South Korea. Flow discharged from Namgang darn for a flood control runs Kahwa river and finally reaches Sacheon bay. In a rainy or typhoon period, the discharged flow can inundate and affect the hydraulic stability and safety of estuarine areas of Kahwa river, Sacheon river, Jungseonpo river, and Jukcheon river. In this study, we performed a 3-dimensional hydraulic experiment and numerical analysis to analyze the level of water rise in the estuarine areas and environmental effect to Sacheon bay by the change of discharge of Namgang dam. A hydraulic model, based on bathymetric and aerial LIDAR survey data, was made in the scale of 1/50. The experimental and numerical results were compared with the observational results. From the experimental and numerical results, it reveals that as the amount of discharge from Namgang dam increases, water levels in the estuarine areas of Jungseonpo river and Sacheon river and the industrial area around Sacheon bay significantly increases by the effect of backwater. In addition, analyzing the measured salinity concentration, we also find out that the range of diffusion of discharged water into Sacheon bay and it takes about 20 days to recover the original salinity concentration.