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Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]
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Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? [Monique Fort]

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Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? Presented by Monique Fort at the "Perth II: Global Change and the World's …

Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? Presented by Monique Fort at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

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  • 1. NATURAL HAZARDS, ROAD CONSTRUCTION, INCREASEDVULNERABILITY IN THE NEPAL HIMALAYAS: WHAT FUTUREFOR A DEVELOPING COUNTRY?M. FORT, E. COSSART UMR 8586 PRODIG Global Change and the World’s Mountains Perth, Scotland, September 26-30 2010
  • 2. NATURAL HAZARDS, ROAD CONSTRUCTION, INCREASEDVULNERABILITY IN THE NEPAL HIMALAYAS: WHAT FUTUREFOR A DEVELOPING COUNTRY?M. FORT, E. COSSART UMR 8586 PRODIGOUTLINE-Environmental, geographic context-Methods and functioning of the system-Study cases along the new Kali Gandaki road-Concluding remarks Global Change and the World’s Mountains Perth, Scotland, September 26-30 2010
  • 3. Tibet-China India Jomosom (2700m)Dhaulagiri 8172 m Annapurna 8091 m Benighat (800m)
  • 4. Tibet-China India Jomosom (2700m)Dhaulagiri 8172 m Annapurna 8091 m Monsoon Pre- Monsoon storms Benighat (800m)
  • 5. Landslides of varying size, all rainfall triggered
  • 6. 5 cm a-1The Himalayas:•A collisional range•Average uplift rate: 6-8 mm a-1•River incision keeping pace withupliftConsequences:•High relief, steep mountainslopes•Strong dynamic hillslope-river coupling=> Slope instabilities, the nature ofwhich varying with type of substrate(bedrock vs colluvium), topography, etc.
  • 7. Road construction: a long, difficult and dangerous process 5 cm a-1The Himalayas: a collisional rangeConsequences:•Average uplift rate: 6-8 mm a-1•High relief, stepp slopes•River incision keeping pace with uplift•Slope instabilities
  • 8. Landslides distribution in Nepal (1968-2002) Active landslides, mostly in: Active landslides, mostly in: - Middle Hills (Lesser Himalaya), Middle Hills (Lesser Himalaya), - south of the Greater Himalaya, south of the Greater Himalaya, - and along the roads and along the roads(ICIMOD) (ICIMOD)
  • 9. Methods to assess threats to the road Bedrock nature •Extensive fieldwork and structure •Repeated surveys •Interactions hillslopes-road- river, sediments budgets •Cascading & process- Old landslide response system approach materialActive landslidesand debris flows Threat to the new road River incision Old fluvial material
  • 10. Middle Kali Gandaki
  • 11. 1977 2000 2008New road and bridges  induced development of Beni Ghat Bazaar  more assets  increased vulnerability
  • 12. 1998 Landslide(upstream view)
  • 13. +500m Quartzite and chloritoschists of the upper Lesser Himalaya dip 1998 Wedge failure (north dip + vertical joints) 30mEmplacementof the lake  1.1 M m3  A landslide-dammed lake started to build up rapidly  relative height of +23m reached in 72007 hours
  • 14. Tatopani Village: lower part under water Landslide(downstream view)
  • 15. Sept. 28 1998, 8 a.m. 9 a.m. 3 p.m., 23 m above the river First lake 15 m drop Residual lake depth : 3-to-5 m Definitive drainage, at the onset of the next monsoon (June 1999) Sept. 29 1998, 10 a.m.
  • 16. Inflow (Q) estimated to be 54 m3/s  According to local reports, the lake developed in 7-8 hours
  • 17. Downstream of Tatopani landslide Bank erosion following the landslide dam (1998):landslide breach (1998) 1,1 x 106m3 coarse boulder lag in Upstream landslide the KG channel dam lake: 1,5 x 106m3 Sedimentary archives reflecting older events landslide of similar nature
  • 18. 1978 2000Changes during the last 3 decades 2007Original landscape: set of 3 terracesChannel widening and change inchannel course Bank undercutting and cleaning offof former alluvial terraces  loss ofcultivated lands and village sites Threat to the new road
  • 19. Debris flow dam 6 p.m. Dana villageDistally confined debris fan At the confluence with Kali Gandaki 6.15 p.m. Next morning7 p.m. 6.25 p.m.
  • 20. 2000 Cause of Dana debris- flow ? • Persistent planar landslideBank erosion  occasional damming of the Ghatte khola (during a few hours or days) • When the dam fails: sudden outburst flood  debris flow  widening of river bed  potential losses (crops and cattle) • Occurrence: once or twice a year, when very intense (storm) rainfall.
  • 21. 2000 Very dynamic change of river bed with time:  Channel widening: Bank erosion 15 m wide in 1974 35 m wide in 2009  Bed surface morphology: aggradation/incision stages (short term) in a general trend of river incision2007 (note gabions) 2009
  • 22. April 2009 The Ghatte khola typifies a « landslide watershed », with unsteady landforms and strong debris inputs to the trunk river New road open to traffic in Spring 2008, across the Ghatte khola : undersized bridge => management problems and increased vulnerability for travellers Dec. 2007 360 m2 42 m2
  • 23. April 2009 The Ghatte khola typifies a « landslide watershed », with unsteady landforms and strong debris inputs to the trunk river New road open to traffic in Spring 2008, across the Ghatte khola : undersized bridge => management problems and increased vulnerability for travellers : management problems and increased vulnerability for Dec. 2007 travellers 360 m2 42 m2
  • 24. TALBAGAR DEBRIS AVALANCHE CONE
  • 25. 2318
  • 26. Upstream of debris 2000avalanche cone 2007 2000 2007
  • 27. Comments and implicationsHimalayas: large potential for landslide and debris flowevents, with possible temporary dams, outburst floodsand related damagesThese short term events: most common mode of erosionand sediment transfer that control sediment fluxesoutward this mountain: « minor » events at the Himalayanand geological scale history, yet « huge » events for humanbeingsOther potential, similar hazards may impact settlements andinfrastructures; they represent a major threat to villages and road alongthe full length of the river systemIn the future, indirect threats might arise from:• poor maintenance of the road, hence moregeomorphic hazards => more physical, functionaland economic vulnerabilities to come• collapse of the tourism economy?Uncertainties:• aggravation of natural hazards due toclimate change (monsoon strengthening)?
  • 28. Thank you for your attention Nilgiri South Peak, 6971 mCo-author Etienne COSSART For further details, see FORT & al., Geomorphology, in press

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