HYDRAURIC ANALYSIS ON WATER STAGE CHANGE ALONG THE SUBMERGED WEIR AND TIDES EFFECT IN HAN RIVER

摘要

Sinkok submerged weir in Han river, Seoul Korea was built in early 1980's for the purpose of water level maintenance and protection from sea water intrusion from the estuary. Its length is almost 1 km and 2.4 meter height which has two composite structures of rigid and movable weir. Huge wetland developed as the results of weir construction just down to the weir. However, recently social conflicts for the weir removal occurred for the river rehabilitation and aqua-eco system recover. This study focused on hydraulic analysis, especially water level changes in terms of with and without submerged weir along the tides where the height has 9 meters difference between ebb and high tide. HEC-RAS for the 1-D simulation and SMS for 2-D analysis were used covering 25 km river length and tributaries. Tides time series records and discharge records from upstream dam of 1-year were and 2 submerged weirs as well as 25 bridges were considered in boundaries. Hydraulic data in the 4 gauging stations were collected for the model calibration. Water level changes were reviewed along 4 cases - with/without weir and flood/dry season -The results showed that more than 3 meter difference of water surface fluctuation along up and downstream including wetland as tide changes in a day. The wetland dimension and water quality were also affected along the water level. The contraction of wetland area might cause the changes of aqua habitat to plants and animals. These results make it difficult to make a decision of removal of the submerged weir. A comprehensive analysis of not only hydraulic but also water quality and environmental effect should be considered.