Flood Hazard Assessment in Upstream Region of Chao Phraya River

1. Asia Geospatial Forum 24-26 September, 2013 Flood Hazard Assessment in Upstream Region of Chao Phraya River CHAM TAU CHIA Doctoral Student Graduate School of Engineering, Kyushu University Civil and Structural Engineering cham@doc.kyushu-u.ac.jp http://wikigis.doc.kyushu-u.ac.jp/geo/

2. Introduction Thailand government put efforts to protect its city area from flood. However, 2011 Thai flood still brought huge damage to city area. This research focus on upstream region to study on rivers capacity and flowing. Also, it is important to understand its influence to downstream area of Chao Phraya River.

3. Introduction Based on The World Bank report • Ranking of Costly Disaster • 2011 Japan Earthquake and Tsunami • 1995 Japan Kobe earthquake • 2004 US Hurricane Katrina • 2011 Thailand Flood

4. Introduction The total damage and losses from the 2011 floods in Thailand amounted to THB 1.43 trillion (USD 46.5 billion). Rehabilitation and reconstruction needs over the next two years and beyond are estimated at THB 1.5 trillion (USD 50 billion).

5. Introduction

6. Introduction Position of Gauging System N7A/N67 – Nan River Y17 – Yom River P7A/P17 – Ping River C2 – Chao Phraya River 100km

7. Objectives Simulate past flood model to analyze in details for both factors and risks of 2011 flood. To understand if Control flooding in upstream flooding will able to mitigate downstream flooding. Examine if Bung Boraphet act as key role to minimize damages of flood event.

8. 2.5 m 3.4 m 3 m 2 m 0.8 m 6 m 5.8 m 4 m 10 KM

9. Flood Scenario in Aug- Sept 2011 Aug 6, 2011 Sept 21, 2011 Aug 16, 2011 Based on post-analysis results, an estimation of 1 m as the inundation depth is used to estimate the flood amount as 2500 million m3 at the peak period (lacking data from September 20 and 21) in the Ping and Nan river areas about 100 km upstream from Nakhon Sawan.

10. Research Methodologies • In order to simulate the past flood events • ArcGIS • Produce quantitative results to obtain flood volume for past flood event. • MIKE FLOOD ( MIKE 11 + MIKE 21) • Create mathematical modelling to simulate past flood event then verify with Royal Irrigation Department (RID) and Thai Monitoring System (TMS) data.

11. Result of GIS Analysis < 0 m 0 m > 0 m After Correction using Spline Tool Before Correction using Spline Tool

12. Comparison of Water discharge at STA P17 (Result of MIKE FLOOD) M3/S Total Volume: P17 : 105144.0 m3/s MIKE : 100383.4 m3/s Difference: 4760.56 m3/s (< 400 million m3) Real (RID)

13. Comparison of Water discharge at STA N67(Result of MIKE FLOOD) M3/S Total Water Discharge: N67 : 129548.00 m3/s MIKE : 112909.52 m3/s Difference: 16638.48m3/s (< 1438 million m3) Real (RID) Simulated (MIKE)

14. Comparison of Water discharge at STA C2(Result of MIKE FLOOD) M3/S 21 Sept to 25 Oct Real (RID) Total Volume: C2 : 297058.0 m3/s MIKE : 279254.6 m3/s Difference: 17803.35m3/s (< 1538 million m3) Simulated (MIKE)

15. Comparison of Evaluated Methodology ArcaGIS 6 Aug MIKE 6 Aug TMS 6 Aug ArcGIS MIKE 29 million m3 298 million m3 Total 270 million m3 Total 640 million m3 Different of 370 million m3

16. Comparison of Evaluated Methodology 21 Sept MIKE 21 Sept TMS 21 Sept ArcGIS ArcGIS MIKE Total 5010 million m3 Total 3260 million m3 Different of 1,748 million m3

17. Comparison of Evaluated Methodology ArcGIS 15 Oct TMS 15 Oct ArcGIS 15 Oct MIKE MIKE Total 4270 million m3 Total 3840 million m3 Different of 430 million m3

18. Comparison of Flood Level in between Field Investigation and Simulated Result Flood Level (m) Affected by water level of Bung Boraphet Huge warehouse Nearby dike Affected by water level of Chao Phraya River

19. Land Use Type Affected by Flood Level, 15 October 2011 Area (KM2) Flood level (M) 1m 2m

20. Land use 2010 Affected by flood

21. Type of Affected Land Use based on Capacity Flood Volume, Million M3 Weekly

22. Comparison of Land use changed From Year 1996 to Year 2010 Percentage Land Use Type

23. Land Use Map Year 2010 Year 1996

24. Flood Mitigation Measures Based on 2012 Chao Phraya River basin flood control master plan Forest and Land Rehabilitation/Conservation More Reservoirs Land Use/Development Regulation Protection for Provincial Urban Areas Absorbing Flood Peak and Increasing Income in Irrigated Floodplain

25. Flood Mitigation Measures In order to store amount of 900 million m3, the most effective measures will be absorbing flood peak and increasing income in irrigated floodplain. To store 400 million m3 in mainstream, height of existing dike along mainstream can be increase to enhance its capacity. Bung Boraphet only has the capacity of 30 million m3 with area of 5km2 and water depth of 6m. It is needed to research on other available swamps to store the extra amount of flood volume and use for irrigation areas in the dry season.

26. Conclusions It is clearly those small streams at upstream area able to store 1,200 – 1,500 million m3 during August to September 2011 and ease the flood condition. ArcGIS used data from satellite imagery to produce quantitative results of past flood event. On the other hand, MIKE FLOOD uses hydraulic data to simulate the past event and it able to estimate the future flood for risk reduction.

27. Thank you very much for your attention.