Sedimentation Characteristics of the Lower Nakdong River Upstream of the Nakdong River Estuary Barrage

The Nakdong River Estuary Barrage (NREB) was constructed in 1987 to prevent saltwater intrusion and to provide the sustainable water supply in the upstream channel of the NREB. The upstream channel of the NREB has experienced sedimentation problems requiring annual dredging operation after the construction. The main purpose of sediment dredging is to prevent flooding during late summer. According to the past records, the annual average dredging volume is about 524,170 m₃ in the upstream channel of the NREB. Fluvial changes and sedimentation problems have been continued due to urbanization and development in the watershed as well as construction and management (sediment dredging) of the NREB. However, the sufficient field monitoring and researches for sedimentation characteristics and bed changes have not been performed after construction of the NREB. Therefore, bed elevation changes for 14 years (1990–2003) after construction of the NREB were analyzed using the Hec-6 model and relatively short term changes of bed elevation were simulated using RMA2 and SED2D programs with field data to review the superficial changes. Field survey before and after sediment dredging was conducted at various points of time to examine the natural flushing effect of sediment by moderate and high discharge before flood season (late July to early September) during low tide.