Flood Inundation Mapping under different climate change scenarios in the upper Indus River Basin, Pakistan

Transcription

1 Flood Inundation Mapping under different climate change scenarios in the upper Indus River Basin, Pakistan Sohaib Baig (doctoral student) 16 November 2017 Disaster Prevention Research Institute 1 Kyoto University, Japan

2 Outline: Flood damage in Indus Basin Rationale of study Proposed research methodology Results References 2

3 Flood Damage in the Indus Basin: 21 floods occurred between 1950 and 2010 in the Indus Basin cumulative economic losses of $19 billion killing 8,887 people, and damaging 109,822 villages between Pakistan faced over 10,000 Million US$ in terms of flood damage Monsoonal rains, steep topography, and degraded catchments contribute to high flood peaks in the Indus Basin. A large drainage area and inadequate surface-storage capacity result in high stream flows. Coinciding peaks from the tributaries further add to the flood peaks in the river downstream (ADB 2013). Figure 1: The transboundary Indus basin, with an area size of 1.1 million sq.km, with upper portion resting in the Hindu Kush, Karakorum, and Himalayan ranges. (ICIMOD 2017) 3

4 Flood Damage in the Indus Basin (Government of Pakistan, Ministry of Water and Power) Table 1: Flood Damage in the Indus Basin, Km²= square kilometer; na = not available. sources: Government of Pakistan, Ministry of Water and Power, Federal Flood 4 Commission.

5 2010 Flood Damage in the Indus Basin: (ADB 2013) The 2010 flood caused the greatest damage due to the timing of the flood, embankment breaches etc. Table 2: Flood Damage by Sector and Region, 2010 ($ million) Killed 1,600 people, caused damage totaling over $10 billion. In the country as a whole, the floods damaged nearly 2 million houses and displaced a population of over 20 million. Flood damage occurred mainly in the agriculture and livestock sector (50%), followed by housing (16%) and transport and communications (13%) 5

6 Extreme Rainfall 2010: Table 3: Comparison of the 2010 Monsoon Rainfall with Historical Means (mm) 6

7 Indus Basin Flood 2010: (American Geophysical Union, 2010) Mostly inundated the eastern side of the river approximately 38,600 km 2 (ADB 2013) Figure 2: Flood level intensity in Pakistan

8 Flood damage in 2010: Figure 3: Damage across the country

9 Post 2010 Floods: (ADB 2013) In August and September 2011, the rainfall in Sindh and Baluchistan was 2.5 times higher than during the same months in the past. This high rainfall, combined with poor drainage and a prolonged period of flooding, affected 9.6 million people in an area of more than 27,000 km 2. A total of 200,000 people lost their homes in 17 districts in Sindh and 5 districts in Baluchistan (ADB, Government of Pakistan and World Bank 2011). In October 2012 the rains and the resultant flood affected 4.9 million people (with 571 reported dead) and damaged more than 600,000 houses; they also ruined crops within an area of 500,000 ha (National Disaster Management Authority 2012; United Nations Office for the Coordination of Humanitarian Affairs 2012) 9

10 Floods of : 300,000 people had been affected, more than 32 dead in Chitral, caused by heavy monsoon rain and glacial lake outburst (PDMA 2015). In 2016, 293 people have been killed, and 331 injured across Pakistan due to heavy rains and severe weather events (OCHA, 2016) Figure 4: Floods in Chitral River-July 2015 Figure 5: NASA's IMERG added up rainfall in northwestern Pakistan

11 Rationale of the study: The upper Indus basin (172,173 km sq.) receives heavy snow annually. The snow & glacier melt contributes 70-80% in the stream flows till Tarbela Dam (Hassoun 2016). Previous studies were limited to flash flood analysis that is study period was limited to couple of months (Sayama, et al. 2012) Keeping in the view of the snow & glacier contribution in the river flows their role in the floods cannot be neglected. There is a need to understand the contribution of snow & glacier melt in the upper Indus Basin both currently and future. Figure 6: Tarbela dam on Indus Basin (Ali, et al. 2015) 11

12 Proposed research Methodology: Precipitation Temperature Snow 17 Outflow depth Snow water equivalent Rainfall runoff Inundation Model (RRI) Inundation extent & discharge 12

13 Proposed research Methodology: Precipitation Temperature Outflow depth Snow 17 Snow water equivalent The observed data for snow water equivalent is not available to calibrate snow 17. Rainfall runoff Inundation Model (RRI) Inundation extent & discharge 13

14 Proposed research Methodology: The proposed solution for this shortcoming is to : first simulate the rainfall-runoff process in the basin using HBV model HBV gives discharge hydrograph, contribution of rainfall, snow plus glacier melt and snow water equivalent The simulated discharge, contributions of rain, snow and glacier melt will be compared with other published studies. The good correlation between published and simulated results means an accurate snow water equivalent. With this snow water equivalent the snow water equivalent from snow 17 would be calibrated 14

15 Results: Initially the model is applied on Hunza basin. Basin s drainage area is km 2 The elevation range of the basin is meters, approximately 7500 km 2 (more than half) of basin area is above an elevation of 4500m. almost one-fifth of its area is glacier covered (Shrestha et al. 2015) Figure 2: Stream network, climate stations and stream flow gauging station of the study area 15

16 Results: The annual precipitation records ( ) at 3 stations are: Khunjrab 165 mm Naltar 670 mm Ziarat 297 mm The temperature varies between 20 and -14 degree C at the stations annually. The records of average annual precipitation is almost half of the observed discharge indicating strong under-catch. A correction technique for the precipitation was applied as suggested by (Immerzeel et al. 2011). The suggestion was based upon mass balance of glaciers, evaporation, precipitation & discharge 16

17 Results: 1200 The corrected & actual precipitation are shown in the right. The cumulative precipitation in both cases are 1267mm and 3687 mm. Precipitation (mm/yr) Corrected Recorded The average outflow volume for is 4.67x10¹⁰ m3. The total volume of precipitation after correction is 5.34x10¹⁰ m3. While before applying the correction it was merely 1.74x10¹⁰ m3. Discharge (cubic meter/sec) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Cumulative monthly precipitation for Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monthly discharge for

18 Results: The results of snow 17 are shown on the right. The results of snow water equivalent need to be verified Ziarat SWE outflow mm/day Khunjrab SWE outflow mm/day Month Month mm/day Naltar SWE outflow Month 18

19 Results: Results of initial simulation runs are shown in Figures. The 2 figures on left shows the inundation depths. In both cases the depth is under 2 meters. At the bottom the discharge for 2000 is given which is over estimated in every month except February. But the peaks in the summer match with observed values Discharge (cubic meters/sec) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 19

20 References: Literature: Ali, A. (2013), Indus basin floods: Mechanisms, impacts, and management, Philippines: Asian Development Bank, 2013 Lutz A., Immerzeel W., Kraaijenbrink P., Shrestha A. & Bierkens M. Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts and Extremes. PLOS-ONE (2016). Shaukat Ali, Dan Li, Fu Congbin and Firdos Khan, Twenty first century climatic and hydrological changes over Upper Indus Basin of Himalayan region of Pakistan. Environmental Research Letters 10(1) Shrestha M., Koike T., Hirabayashi Y., Xue Y., Wang L., Rasul G. & Ahmad B. Integrated simulation of snow and glacier melt in water and energy-balanced based, distributed hydrological modeling framework at Hunza River Basin of Pakistan Karakoram region. Journal of Geophysical Research: Atmospheres (2015). DOI: /2014JD Shabeh ul Hasson, Future Water Availability from Hindukush-Karakoram-Himalaya upper Indus Basin under Conflicting Climate Change Scenarios. Climate 2016, 4(3). DOI: /cli Images:

21 Thank You 21