1. flood Modelling of Kalu-Ganga river basin
H. K. Nandalal
Department of Civil Engineering University of Peradeniya Peradeniya Sri Lanka

2. Introduction
Problems related to flooding have greatly increased over recent decades because of
population growth
development of extensive infrastructures in close proximity to rivers
It is importance to find solutions by
utilizing modern technology like Geographic Information Systems (GIS), Remote Sensing (RS) and
flood modeling

3. Outline of the Presentation
Study area
Data used
Software used
Application of Software
HEC-HMS
HEC-RAS
ENVI

4. Study Area Kalu-Ganga river basin in Sri Lanka
Total catchment area is km2
Entire basin lies within the wet zone.
Average annual runoff is around 7600 MCM.
Catchment experiences average annual rainfall of 4000 mm.

5. Study Area Study concentrates on the lower reaches of the river
Area of interest is nearly 500 km2
This includes 5 Divisional Administrative Divisions (DSD)

6. Data Used

7. Data used
TIN Model of the Study area
Contour Data
LIDAR DATA

8. Data used
Locations of rainfall and discharge gauging stations

9. Data used Satellite images
Raw Images (Dry Date, 03 March,2008) ALOS – PALSAR (HH)
Raw Images (Wet Date, 03 June,2008) ALOS – PALSAR(HH)

10. Data used
Data Collection and Data-basing…

11. Application of HEC-HMS
Rainfall –Runoff Modeling

12. Application of HEC-HMS
Basin model developed using HEC-GeoHMS

13. Application of HEC-HMS
Results of the verification runs to compare the simulated flows and the observed flows of the calibrated HEC-HMS model

14. Application of HEC-RAS
Flood Modeling

15. Application of HEC-RAS
Geometric Data: HEC-GeoRAS export
Stream C/L
River banks
Flow paths

16. Application of HEC-RAS
Discharge data obtained from HEC-HMS
Mawakoya
Elagawa
Junction Mawakoya/Kalu Ganga
Kuda Ganga
Junction Kuda Ganga/Kalu Ganga
Flow (m3/s) data at\Return Period
10yr
20yr
50yr
100yr
Elagawa
1062.6
1319.7
1798.1
2605.5
Junction KudaGanga/ Kalu Ganga
1455.7
1836.9
2524.4
3743.3
Mawak Oya
97.5
122.2
174.4
245.5
Junction Mawak Oya/Kalu Ganga
1079.5
1340.5
1828.5
2647.7
Kuda Ganga
414.4
555.3
817.1
1260.7

17. Application of HEC-RAS
HEC-RAS output

18. Application of HEC-RAS
HEC-RAS output

19. Application of HEC-RAS
Flood Hazard Maps from HEC-RAS

20. Verification of model result by satellite data
Raw Images (Dry Date, 03 March,2008) ALOS – PALSAR (HH)
Raw Images (Wet Date, 03 June,2008) ALOS – PALSAR(HH)

21. Band Math Image (WET-DRY)
(Difference dB image Wet - Dry)
Mask

22. Flood extent resulted by satellite data

23. Comparison of the Flood extent derived from HEC-RAS model and Satellite image

24. Final Flood Hazard Maps

25. Thank you for your patience.
Questions?