Satellite evidence of mass movements in the Se< basin, 2002-‐2012 OBSERVATION: ASTER shows many small rockfalls, debris ﬂows, or other changes in the gorge. OBSERVATION: ASTER shows a large rockfall into the gorge between 2002 and 2008. OBSERVATION: ETM+ imaging suggests a renewed rockfall at the same site between March 19 and April 20. INFERENCE: Repeated rockfalls at the same site. INFERENCE: Rockfall damming may have occurred in either the weeks before the outburst ﬂood or in the years before. OBSERVATION: The ﬂood was preceded by less than an hour with an unusually large debris-‐snow avalanche.
Detail geological mapping at 1:25000
Geological map of the Se< River basin north of Pokhara.
Geological cross-‐sec<on across the Pokhara valley. km 6
Approximate profile of the Seti River
Seti Gorge (Carbonate rocks)
Upper Seti Basin
Calc-schist & marble
Pelitic schist & quartzite
Migmatites & augen orthogneiss
Phyllite & metasandstone
Tethys Himalaya Laminated limestone Black schist Marble & schist
Quaternary Sediments Annapurna Formation Seti River Terraces
Photomicrographs of metasedimentary rocks in the Annapurna region
X-‐ray diﬀracCon paOerns of the clay-‐sized fracCons of the Kharapani sample (black) and SeC dust (red). The two diﬀractograms perfectly match showing similar mineralogical composiCon.
2-Theta - Scale File: kharapani. raw - Type: 2Th/Th locked - Start: 2.000 ° - End: 50.000 ° - Step: 0.010 ° - Step time: 0.6 s - Temp.: 25 °C (Room) - Time St arted: 0 s - 2-Theta: 2. 000 ° - Theta: 1.000 ° - Display plane: 1 - Anode: Operations: Import File: Seti Dus t_Add_Scans.raw - T ype: 2T h/Th lock ed - Start: 2.000 ° - End: 50.000 ° - Step: 0.010 ° - Step time: 0.6 s - Temp.: 25 °C (Room) - Time Started: 0 s - 2-Theta: 2.000 ° - Theta: 1. 000 ° - Display plane Operations: Add Scans | Import
Site overview: Flash Flood in Seti River
Destruc<on Kharapani Site
Site Siteoverview: overview:Flash FlashFlood Floodin inSeti SetiRiver River
20 m Height
10 m height
Site overview: Flash Flood in SeV River
Destruc<on Masina Bagar
Flood Inunda<on Mapping
Socio economic survey
Flood vic<ms from Sandal village
Affected area of Seti River
Destruc<on of Bridge Kharapani Site
Pokhar drinking water supply pipe damaged by seV ﬂood
Sano Khobang: Resettlement of victims
VDC/Municipality Machhapuchre Sardikhola Ghachowk Lahachowk Puranchaur Hemja Lamachaur Total
Number of Household 395 879 588 829 865 3019 1745 68236 76556
Number of household and population, 2011 Source: CBS, 2013. * Field Survey, 2013
Total Population 1729 3442 2707 3129 3597 12262 7027 255465 289358
Affected Household* 8 7 0 0 0 17 0 0 32
Public dissemination of Iindings of Seti Ilood Havoc May 5 2012
If we ignore
FLOOD Phewa Lake
Natural Hazards, unplanned Sehlements and its impacts
Calving front of Thulagi Glacier and the lateral moraine.
Drainage over the end moraine dam of Thulagi Lake.
Ponds on the end moraine. This may indicate a thermokars<c process involving thawing of ice contained in the moraine.
Why do we care about Thulagi Lake and possible outburst ﬂoods from it?
Unplanned serlement and natural hazard Eg., Urarakhand, India
Ques<ons ? 1. When to install early warning system ?
ATer or before the disaster ???
2. Is early warning system itself enough to minimize the risk ? What role can we scienCsts play to minimize the risk ?
Published on Sep 26, 2013
Slides for presentation given to High Mountains Adaptation Partnership in Huaraz, Peru on 13 July 2013.