Integrated Approach for Flash Flood Prediction and Management: A Case Study of Poiqu Bhotekosi Basin

1. Integrated Approach for Flash Flood Prediction and Management: A case study of PoiquBhotekosi Basin Rajesh Thapa, Arun Bhakta Shrestha (ICIMOD) Narendra Khanal (TU), & Pawan Ghimire (GISIDC) International Disaster and Risk Conference IDRCDavos, 2010

2. International Centre for Integrated Mountain Development (ICIMOD) – an intergovernmental organisation with 8 member countries Vision: The mountain population of the greater Himalayas enjoys improved well-being in a sustainable global environment Mission: To enable and facilitate the equitable and sustainable well-being of the people of the Hindu Kush-Himalayas by supporting sustainable mountain development through active regional cooperation. www.icimod.org

4. Adaptation to Environmental Change and Ecosystem Services

7. Water related disaster is the most commonWATER TOWER OF SOUTH ASIA! Sustaining over 2 b people in the River basins Impacting on food and energy production of 3 b people

8. UNDP, 2004 Average Population Exposed to Flood per million

11. Consists of 151 glaciers with an area of about 232 km2 and 139 glacial lakes with an area of 16 km2 within China out of which 9 are potentially dangerous lakes

12. The basin already experienced 3 GLOFs in the past, 1935 when Tara Co lake burst out; in 1964 & 1981 Zhanzanbo lake brust out.

13. Apart from GLOF the basin is frequently affected by intense rainfall, one such flash floods occurred in 1987, and caused serious damages.

15. Its surface area is 3.84 sq.km and length is 3.2 km. Its altitude is 5089m (masl).

17. Development of Ganxi Co and LumiChimi lakes Glacier 1977 1984 1990 1996 2000 2003

18. Results of Dam Break Model (20m. Breach)

19. Results of Dam Break Model INPUT PARAMETERS Breach Depth = 20m Breach Width = 56.1m Time of Failure = 0.75 hrs. Manning’s n = 0.035 Breach Side Slope = 1.15

20. Flood inundation Scenario

22. 944 Ha land exposed to GLOF (235 Ha agriculture)

23. 16,000 people will be directly impacted; 640,000 indirectly impacted

27. Finding from the Poiqu/BhoteKosi Case Study GLOFs, Flash flood risk assessment should be conducted in a holistic manner Need to look at the upstream-downstream linkages Step-wise approach will result in better risk assessment Systematic risk assessment provides understanding of both hazard (physical) and vulnerability (physical and social)

28. Cont.. Expansion of early warning system and establishment of flood marks along the river based on the model results Land use guidelines, building codes and standards Preparedness for rescue/relief operation including emergency relief fund (package) and insurance Regular monitoring of glacier lakes,LDOF and risk communication Implementation of awareness raising programmes such as drama, film show, workshops etc. at the local level

29. Thank You! www.icimod.org Rajesh Thapa rthapa@icimod.org