Integrated Approach for Flash Flood Prediction and Management: A Case Study of Poiqu Bhotekosi Basin
Integrated Approach for Flash Flood Prediction and Management: A case study of PoiquBhotekosi Basin<br />Rajesh Thapa, Arun Bhakta Shrestha (ICIMOD)<br />Narendra Khanal (TU), & Pawan Ghimire (GISIDC)<br />International Disaster and Risk Conference IDRCDavos, 2010<br />
International Centre for Integrated Mountain Development (ICIMOD) – an intergovernmental organisation with 8 member countries<br />Vision: The mountain population of the greater Himalayas enjoys improved well-being in a sustainable global environment<br />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.<br />www.icimod.org<br />
Three Strategic Programs<br /><ul><li>Sustainable Livelihoods and Poverty Reduction
Adaptation to Environmental Change and Ecosystem Services
Integrated Water and Hazards Management</li></li></ul><li>Integrated Water and Hazard Management<br />IWM, Gender,….<br />AA1.1 Monitoring <br />and assessment of <br />ice and water resources<br />AA1.2 DRR & Community <br />Resilience<br />Risk Analysis using <br />Scientific and <br />Local Knowledge<br />AA1.3 <br />Strengthening<br />U/S-D/S Linkages<br />Data Sharing, <br />Early Warning, <br />Basin wide scenarios<br />Building <br />Capacities <br />+<br />Awareness <br />on DRR<br />+<br />Database Development<br />Livelihood, well being<br />
10 Large River Basins <br /><ul><li>Natural hazards are common
Water related disaster is the most common</li></ul>WATER TOWER OF SOUTH ASIA!<br />Sustaining over 2 b people in the River basins<br />Impacting on food and energy production of 3 b people<br />
UNDP, 2004<br />Average Population Exposed to Flood per million<br />
Water related hazards<br /><ul><li>Flash flood has the highest mortality rate</li></ul>Jonkman, 2005<br />
Flash Flood in Poiqu/BhoteKosi Basin: Case study <br /><ul><li>The Poiqu basin is trans-boundary between China and Nepal and is named SunKoshi- BhoteKoshi in Nepal.
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
The basin already experienced 3 GLOFs in the past, 1935 when Tara Co lake burst out; in 1964 & 1981 Zhanzanbo lake brust out.
Apart from GLOF the basin is frequently affected by intense rainfall, one such flash floods occurred in 1987, and caused serious damages.
The bhairabkund LDOF of 1996, 1998, 1999 and Devisthankhola LDOF of 1999, 2002 and 2005 are some example of past LDOF in the basin. The most remarkable LDOF events is the Larcha LDOF of 22nd July 1996 killed 54 people, 22 houses washed away and 150 meters of Arniko highway was destroyed. </li></li></ul><li>LUMU CHIMI GLACIER LAKE: Case study area<br /><ul><li>Limu Chimi lake lies in Poiqu basin, enlisted as potential danger lake in the basin.
Its surface area is 3.84 sq.km and length is 3.2 km. Its altitude is 5089m (masl).
Vol. Of Lake = 153.6 m.m3</li></li></ul><li>The stepwise approach<br />Existing Inventory of glacial lakes<br />Update Inventory of glacial lakes<br />A set of criteria<br />A list of potentially dangerous lakes<br />Reconnaissance/ Stakeholders’ priority<br />Priority list<br />Detailed field-based study<br />Physical/social/ Economical<br />Downstream impact assessment<br />Mitigation/adaptation strategies<br />Ranking of the lakes<br />
Development of Ganxi Co and LumiChimi lakes<br />Glacier<br />1977<br />1984<br />1990<br />1996<br />2000<br />2003<br />
Results of Dam Break Model (20m. Breach)<br />
Results of Dam Break Model<br />INPUT PARAMETERS<br />Breach Depth = 20m<br />Breach Width = 56.1m<br />Time of Failure = 0.75 hrs.<br />Manning’s n = 0.035<br />Breach Side Slope = 1.15<br />
Downstream Socioeconomic impact Assessment:<br />No of Household & Population<br /> Likely to be Affected<br /><ul><li>High value elements are at risk
944 Ha land exposed to GLOF (235 Ha agriculture)
16,000 people will be directly impacted; 640,000 indirectly impacted
Property at risk about USD 200 million</li></li></ul><li>
Preparedness activities:<br />After<br />Change in road alignment and bridge design<br />Establishment of early warning system by BhoteKoshi Hydroelectricity project (but very short lead time)<br />Before<br /><ul><li> Training to local people on early warning system and placement of signboards about siren system
Bioengineering and runoff management for the stability of toe slope</li></li></ul><li>Local level workshop on Dissemination and interaction programe<br />
Finding from the Poiqu/BhoteKosi Case Study<br /> GLOFs, Flash flood risk assessment should be conducted in a holistic manner<br />Need to look at the upstream-downstream linkages<br />Step-wise approach will result in better risk assessment<br />Systematic risk assessment provides understanding of both hazard (physical) and vulnerability (physical and social)<br />
Cont..<br />Expansion of early warning system and establishment of flood marks along the river based on the model results<br />Land use guidelines, building codes and standards<br />Preparedness for rescue/relief operation including emergency relief fund (package) and insurance<br />Regular monitoring of glacier lakes,LDOF and risk communication<br />Implementation of awareness raising programmes such as drama, film show, workshops etc. at the local level<br />