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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

Pokhara valley

Approximate profile of the Seti River

Seti Gorge (Carbonate rocks)

km

Upper Seti Basin

6

4

4

2

2

0

0

-2

-2

A (sw)

Lesser Himalaya

B (sw)

Higher Himalaya

Calc-schist & marble

Calc-gneiss

Pelitic schist & quartzite

Migmatites & augen orthogneiss

Phyllite & metasandstone

Kyanite-bearing paragneisses

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.  

140

130

Quartz+Muscovite

120

110

Calcite

100

70

Quartz

60

Calcite

50

Calcite

Muscovite

40

Calcite

Calcite

Calcite

80

Albite

Lin (Counts)

90

30

20

10

0 5

10

20

30

40

50

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  


Upper Seti

Affected area of Seti River

Middle Seti

Lower Seti

Pokhara


Damaged Infrastructure

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    


Annapurna III  

Annapurna IV  

Machhapure

If we ignore

Sardikhola Ghachok  

Hemja

Lamachaur

FLOOD Phewa  Lake  

Pokhara

Begnas Lake  

Bharatpokhari


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  ?  


Thank You  


Study team  


Dhananjay Regmi: Seti River disaster and hazards facing Pokhara, Nepal (part 3 of 3)  

Slides for presentation given to High Mountains Adaptation Partnership in Huaraz, Peru on 13 July 2013.

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