1. 2010 1 August 20th, 2010

2. CONTENT 1. Introduction 2. Data and Characteristics 3. Flood analysis 1. MOUSE 2. SOBEK 3. ARC-SWAT 4. Conclusions and suggestions 2

3. INCHEON Located in the mid-west Korea peninsula near Yellow sea With both international port and international airport The third biggest city in Korea Population : 2,730,000 INTRODUCTION 3

4. 4 Reclamatation area used for industry and residence Total area : 34 km² Most of the present Incheon Gyo watershed has been sea before reclamatation was completed in 1985

5. DATA AND CHARACTERISTICS 5 Annual mean precipitation in Incheon in the last 30 years 64% of annual precipitation

6. DATA AND CHARACTERISTICS 6 Time (h)Rainfall (mm) 4:00:00 AM0 5:00:00 AM0 6:00:00 AM12 7:00:00 AM17 8:00:00 AM55 9:00:00 AM75 10:00:00 AM45 11:00:00 AM8 12:00:00 PM9 1:00:00 PM8 2:00:00 PM7 3:00:00 PM5 4:00:00 PM1 5:00:00 PM0 6:00:00 PM0 Flood event : 4th August 1997, 04 AM~06 PM

7. DATA AND CHARACTERISTICS 7 PRECIPITATIONS 4th August 1997 Rainfall intensity 20 years 50 years 80 years 100 years PRECIPITATIONS 4th August 1997 Rainfall intensity 20 years 50 years 80 years 100 years

8. DATA AND CHARACTERISTICS 8

9. 9 Peak : 78.29 mm/h Peak : 96.67 mm/h Peak : 111.99 mm/h Peak : 107.07 mm/h

10. DATA AND CHARACTERISTICS 10 Gate Data Tidal difference about 9 m When sea level up to EL.(+) 2.3 m(gate height) must be close during 6 hours twice of day Main culvert outlet invertlevel is EL.(-) 0.09 m To drain rainwater effected by reservoir water level (Backwater)

11. 1D model Analysis of pipe network Steps: 1. Imput data to the software 2. Flooding analysis 3. Improvements on the pipe network to reduce flooding 11 MOUSE

12. 12 50 years return period FLOOD ANALYSIS

13. 13 80 years return period FLOOD ANALYSIS

14. 14 100 years return period FLOOD ANALYSIS

15. 15 FLOOD ANALYSIS Comparison between 20 and 50 years return period

16. 16 FLOOD ANALYSIS Comparison between 80 and 100 years return period

17. 17 Reason of Flooding FLOOD ANALYSIS

18. 80 years Comparison of change in pipe diameter and run-off coefficient 0.6 18 IMPROVEMENTS TO REDUCE FLOODING

19. 19

20. 20 IMPROVEMENTS TO REDUCE FLOODING

21. Connecting pipe system at one node Result: shows before and after 21 IMPROVEMENTS TO REDUCE FLOODING

22. 1D vs 2D models 22 Manholes (1D) 1D can not represent flooding in depressed areas where there are no manholes. 1D can not represent flooding between structures or buildings, where there are no manholes 1D models can study the pipes capacity. However: Moreover a 2D model can be very useful to distribute the manholes in a good way.

23. 23 2D Hydraulic and Hydrological study with SOBEK Rain as a direct input of the model Proposal: Study of Overland flooding caused by inadequate storm water drainage systems. Advantages: A separate hydrological model is not required. The hydraulic model is used for rainfall runoff routing. 23

24. 24 SOBEK characteristics Coupled 1D-2D model. 2D grid with square elements. Solve Saint-Venant equations 24

25. 25 2D model of terrain, buildings and structures Hydrological Study for sub-basin delimitation High resolution of the model High computational cost (time consuming) Limitation Reduction of the Study area to a sub-basin. ARC-SWAT 25

26. 26 Processing of the DEM interpolating: Manholes elevation Contour Digital Elevation Model (DEM): SWAT & SOBEK inputs 26

27. 27 ARC-SWAT ArcGIS-ArcView extension. SWAT (Soil and Water Assessment Tool) is a river basin scale model developed to predict the impact of land management practices on water, sediment, and agriculture. We use: Generation of the sub-basins with the DEM as a unique input. 27

28. 28 Selection of the sub- basin with: Reported flooding in 1997 Downstream bond. Condition known No drainage system (manholes) Does not recieve water from other sub-basins Flooded Areas (1997) Main flow discharge Manholes Sub-basin selection 28

29. 29 Yellow sea Flooded Area in 1996 Basin characteristics: AREA = 42 km2 Soil use: URBAN Infiltration will not be considered. 29

30. 30 Modeling of the 2D structures is important in order to evaluate flooding in the area. The structure of the railway is modifying the natural flow. Flooded area in 1996 30

31. 31 Modeling of the buildings Option 1: Elevation of the DEM overlapping the buildings shape file (resolution=5x5m) 31

32. 32 Option 2: Increase the roughness of buildings Manning Coeff. 0.03 Building Manning Coeff.=0.1 Other = 0.014 32

33. 33 Comparison of the two methods

34. 34 Sobek Interface Input 2D and 1D schemes Input Precipitation Simulation Settings

35. 35 But after two days trying to run the model.. SOBEK didn ’ t RUN! We suppose that is a software problem with the server cause it didn ’ t run even for the most simplified case in 1D. The expected results will be similar than the video showed: 35

36. 36

37. Conclusions and improvements Different software were used to generate results (Arc-GIS, MOUSE, SOBEK, SWAT) Several succesful simultaion were run in MOUSE for different return periods. Some pipe modifications were proposed to reduce flooding in some areas. No result was generated by SOBEK. However it is necessary to evaluate flooding with a 2D. Different approaches were worked out to reduce flooding in the future. 37

38. 38 Thank you ！