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WATER CIRCULATION STUDY FOR THE DEVELOPMENT OF SONGDO WATERFRONT’S CANAL SYSTEM International Conference on Flood Resilience Experiences in Asia and Europe Dongwoo JANG 1 , Cristina AGAFON 1 , Gyewoon CHOI 2 1 International Center for Urban Water Hydroinformatics Research & Innovation, South Korea 2 Dept. of Civil and Environmental Engineering, Incheon National University, South Korea 5-7 September 2013 Exeter United Kingdom Abstract (Tahoma 48pt) Songdo city is currently developing the waterfront near the coastline which is in line with its goal of being a world class eco-friendly green city in Incheon. The city planned to have a canal system surrounding it where clean sea water will flow in these canals. There is a need to ensure that situations like stagnant waters and excessive flow velocities will not occur. Also there is also a water quality problem. In order to do this, a 3D numerical model, MIKE 3 FM was used to investigate the water circulation system with respect to the operation of the four water gates present at the ends of the canal system, where ideal configurations of the gate operations and water interaction with sea and canal water will be determined. Songdo Area References •Sobey R. J. (2001). Evaluation of numerical models of flood and tide propagation in channels. In: Journal of Hydraulic Engineering / October 2001, 805-824 •Durbarbier B., Castelle B. (2011). Numerical modeling investigation of the influence of tide on the formation and subsequent nonlinear evolution of rip channels. In: Journal of Coastal Research, Special Issue 64, 1018 – 1022 •Scott S.H., Jia Y. (September 19-21). Simulation of sediment transport and channel morphology change in large river systems. US-China Workshop on Advanced Computational Modelling In Hydroscience & Engineering. http://www.irtces.org/zt/us_China/proceedings/scott_man_Revised.pdf (accessed 10 June 2013) •Szymkiewicz R. (2010). Numerical Modeling in Open Channel Hydraulics. In: Water Science and Technology Library, Volume 83. Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Poland CONCLUSION Model Setup The bathymetry of the channel system was built with the Mesh Generator from MIKE 3 FM, using the coordinates extracted from a CAD file of Songdo area and the elevation given for each channel as input values . Simulation Results Figure 1. Incheon, South Korea Figure 2. Songdo Waterfront Plan Figure 3. Water Quality Index(2012)> Figure 4. Set up the Unstructured Mesh The tidal wave for 15 days was provided by KHOA and tidal harmony is considered M2, S2, K1, O1 which is available only for the Incheon area. Figure 5. 15days Tidal Condition in Incheon At each entry/exit should be placed a weir. For the input the weir height was set at a El. (+)0.5 m and 50 m width and weir height El. of (-)1.0 m with a weir width of 10 m at the output. Figure 6. Weir Height at the Entry and Exit There are 4 cases with different input and output conditions that were simulated using the Hydrodynamics and Transport module in MIKE 3 FM in order to see the direction of the water flow and water exchange ratio for 15 days tidal. -Case 1- -Case 2- -Case 3- -Case 4- Figure 7. 4 Cases of the Water Circulation for the Songdo Canal System Classification Entry gate Exit gate Position Weir EL. (m) Weir width (m) Position Weir EL. (m) Weir width (m) Case 1 South 1 Gate (+)0.5m 50m North 2 Gate (-)1m 10m Case 2 North 1 Gate South 2 Gate Case 3 South 1 & North 1 Gate South 2 & North 2 Gate Case 4 South 1 & South 2 Gate North 1 & North 2 Gate Figure 8. Entry and Exit gate condition for each case Figure 9. Data Extraction Points Maximum Velocity in Canal Maximum Tidal Condition Maximum Velocity (cm/s) N1 N2 N3 W1 W2 W3 E1 E2 E3 S1 S2 S3 Case 1 0.9 4.3 10.3 43.8 16.6 37.3 41.2 12.4 23.3 9.0 9.7 7.0 2 11.7 34.3 24.6 27.1 18.0 61.7 22.2 12.2 43.5 3.2 2.5 2.2 3 4.9 14.3 7.5 9.0 2.3 19.4 14.9 3.6 5.5 5.3 6.0 3.0 4 1.0 2.3 9.3 42.6 16.3 37.0 39.1 11.8 24.8 1.7 3.4 5.8 The maximum velocity reached is 61.7 cm/s (Case 2). If the velocity is higher, it will create an erosion problem for the bed area. It is recommended that the velocity inside the canal should be below 50cm/s in order to maintain a stable ship movement. Water Exchange Ratio from Sea Water to Canal Water The next table is showing the percentage of polluted water exchanged with clean water through a natural flow from sea and also the day when 90% of the water was exchanged. Case Elapsed Time (day) 90% Exchange d Time (day) 0.5 5 10 15 All Canal Case 1 6.9 66.2 97.2 99.2 7.7 Case 2 5.8 68.9 99.3 99.5 7.2 Case 3 6.8 73.4 87.6 95.8 11.8 Case 4 6.1 42.9 56.4 61.7 X Next graph is showing the ratio of remained canal water at each canal The figure below is showing how the water is traveling through the channel and how fast it reaches the outflow. Case 1, 2 have a more fast exchange with sea water compared with case 3, 4. The result from Case 1 and 2 are showing a high exchange ration and a 7 days duration for a 90% exchange inside the canal. CASE Elapsed time 0.1 day 5 day 10 day 15 day Case 1 Case 2 Case 3 Case 4 Sea water more than 90% The purpose of the current study was to find the most benefiting way of water circulation through the system. Canal water and sea water is mixed by gate operation in canal. The numerical modeling of the water flow helped to determine the gate operation that will play an important part in the water circulation. For each inflow or outflow boundary was set an opening and a closing level so that it can be used as a guide in the real situation. Observing and comparing the various simulation results, but also the real threats that can have a big influence on the quality of the system, case 1 (South 1 gate input, North 2 gate output) was selected as the most appropriate to be implemented in Songdo waterfront area.
