NATURAL HAZARDS, ROAD CONSTRUCTION, INCREASEDVULNERABILITY IN THE NEPAL HIMALAYAS: WHAT FUTUREFOR A DEVELOPING COUNTRY?M. ...
NATURAL HAZARDS, ROAD CONSTRUCTION, INCREASEDVULNERABILITY IN THE NEPAL HIMALAYAS: WHAT FUTUREFOR A DEVELOPING COUNTRY?M. ...
Tibet-China                                                 India                               Jomosom (2700m)Dhaulagiri ...
Tibet-China                                                 India                               Jomosom (2700m)Dhaulagiri ...
Landslides of varying size, all rainfall triggered
5 cm a-1The Himalayas:•A collisional range•Average uplift rate: 6-8 mm a-1•River incision keeping pace withupliftConsequen...
Road construction: a long,  difficult and dangerous process              5 cm a-1The Himalayas: a collisional rangeConsequ...
Landslides distribution in Nepal (1968-2002)                              Active landslides, mostly in:                   ...
Methods to assess                                                  threats to the road                         Bedrock nat...
Middle Kali Gandaki
1977                            2000                                                    2008New road and bridges  induced...
1998 Landslide(upstream view)
+500m   Quartzite and chloritoschists of                        the upper Lesser Himalaya                                 ...
Tatopani Village: lower                       part under water   Landslide(downstream view)
Sept. 28 1998, 8 a.m.                     9 a.m.    3 p.m., 23 m above the river                 First lake         15 m d...
Inflow (Q)                                                  estimated to                                                  ...
Downstream of    Tatopani landslide Bank erosion following     the                            landslide dam               ...
1978    2000Changes during the last 3 decades                                         2007Original landscape: set of 3 te...
Debris flow dam                                    6 p.m.     Dana villageDistally confined debris fan               At th...
2000   Cause of Dana debris-               flow ?               • Persistent planar landslideBank erosion    occasional d...
2000    Very dynamic change of                         river bed with time:                           Channel widening:  ...
April 2009   The Ghatte khola typifies a             « landslide watershed », with             unsteady landforms and stro...
April 2009   The Ghatte khola typifies a             « landslide watershed », with             unsteady landforms and stro...
TALBAGAR DEBRIS AVALANCHE CONE
2318
Upstream of debris   2000avalanche cone              2007                     2000   2007
Comments and implicationsHimalayas: large potential for landslide and debris flowevents, with possible temporary dams, ou...
Thank you for your attention                             Nilgiri South Peak, 6971 mCo-author Etienne COSSART   For further...
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? ...
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? ...
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? ...
Natural hazards, road construction, increased vulnerability in the Nepal Himalayas: what future for a developing country? ...
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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 Mountains" conference in Perth, Scotland in September 2010.

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

  1. 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. 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. 3. Tibet-China India Jomosom (2700m)Dhaulagiri 8172 m Annapurna 8091 m Benighat (800m)
  4. 4. Tibet-China India Jomosom (2700m)Dhaulagiri 8172 m Annapurna 8091 m Monsoon Pre- Monsoon storms Benighat (800m)
  5. 5. Landslides of varying size, all rainfall triggered
  6. 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. 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. 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. 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. 10. Middle Kali Gandaki
  11. 11. 1977 2000 2008New road and bridges  induced development of Beni Ghat Bazaar  more assets  increased vulnerability
  12. 12. 1998 Landslide(upstream view)
  13. 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. 14. Tatopani Village: lower part under water Landslide(downstream view)
  15. 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. 16. Inflow (Q) estimated to be 54 m3/s  According to local reports, the lake developed in 7-8 hours
  17. 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. 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. 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. 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. 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. 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. 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. 24. TALBAGAR DEBRIS AVALANCHE CONE
  25. 25. 2318
  26. 26. Upstream of debris 2000avalanche cone 2007 2000 2007
  27. 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. 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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