The Four Major Rivers Restoration Project: Impacts on river flows: Fid-Bau Portal

The Four Major Rivers Restoration Project: Impacts on river flows

Jun, Kyung Soo / Kim, Jin Soo

Abstract The ongoing Four Major Rivers Restoration Project will drastically change the river environment of South Korea. The objective of this study is to evaluate the impact of the Four Major Rivers Restoration Project on river flows using an unsteady flow simulation model. The computational model was applied to the stream reaches of the Han River and the Nakdong River. Historical floods were simulated for the changed river environment as well as for the current river condition to investigate the flood mitigation effect of the project. The simulation results show that once the project is completed, the flood water level of the entire reach of both rivers will fall because water level decline due to the channel dredging dominates water level rise due to the presence of weirs. This mitigation effect was particularly significant for the upstream region of the Nakdong River because of large-scale dredging. A steady flow simulation was carried out using normal flow discharges to investigate the effect of the project on flow characteristics during non-flood periods. For the Han River, the normal water level rises upstream of the weirs, whereas it falls downstream owing to the dominant dredging effect. However, in spite of heavy dredging, the water level decline in the case of the Nakdong River is very limited because the effect of dredging is overwhelmed by the high normal pool level of the weirs. The increase in flow travel time of the Nakdong River after the completion of the project will be more significant than that of the Han River.