1. Landslide Disaster and Hazard Zonation in theLandslide Disaster and Hazard Zonation in the
parts of Khaptad area, Achham districtparts of Khaptad area, Achham district
by the landslides of 26-27 August 2006by the landslides of 26-27 August 2006
byby
Birendra Piya (Sr. Div Geologist)Birendra Piya (Sr. Div Geologist)
G. R. Chitrakar (Sr. Div Geologist)G. R. Chitrakar (Sr. Div Geologist)
S. P. Manandhar (Geologist)S. P. Manandhar (Geologist)
Department of Mines and GeologyDepartment of Mines and Geology
April 1,April 1, 20072007
3. IntroductionIntroduction
Due to the continue 3 days heavy rainfall starting from 25
August to 27 august 2006 in the far western region,
landslide disaster took place causing huge damage in the
life and property.
The study area lies in the most remote place of Khaptad
VDC of Achham District, Far western Nepal, It is about 455
Km away from Nepalgunj up to Sanfebagar by road and
from Sanfebagar it is one full day walk towards the Khaptad
national park.
The field program was conducted from 10/10/06 to
18/10/06.
The study was carried out upon the request of Disaster
Relief Committee Home Ministry, Nepal Government
4. ObjectivesObjectives
To study the geological conditions of the area and
to investigate the cause of disaster.
To investigate whether the region is safe for the
continue settlements for the people of the area or
need to be relocated them in some other safe areas.
Finally, to prepare a report with some
recommendations.
5. Methods
A toposheet map (sheet no. 2989 09D)
of scale 1:25000 was used as a base
map.
Field Survey and Interviews with the
local people were carried out in the
field.
Ilwis 3.3 Academic version developed
by ITC, Netherlands was used for the
GIS analysis to prepare landslide
Hazard Zonation map.
6. Present Scenarios;
The Balyalta Village and Guta Villages are the most
affected area by the landslide disaster. The people of
the villages have been rehabilated in a temporary
rehabilitation center situated at a close distance from
their respective villages.
Many landslides along with major cracks in and
around the villages have been developed.
Even the rehabilitation center is located at a landslide
risk zone.
The individual houses in the village have been
completely abandoned.
7. The people in the rehabilitation center are lacking
of warm clothes and safe shelter.
The loss of life and properties of the people due
to landslide disaster is given below in the tabular
form.
Contd. Present Scenarios;
8. Details of the lossDetails of the loss
Disater Effects
No.
Village Name Household Pop Human Injured House Landlosswatermill
Casualties Cow& Buffa.Goatsdamagedin ropanidestroyed
Guta Village 21 147 1 2 34 3 13
Balyalta Village 92 556 6 8 64 94 6 2000
Putru Village 48 327 0 0 15 7 403 3
Mathillo Tuka 66 483 0 0 0 208
TalloTuka 57 385 0 0 0
Bhedasen-9 32 201 0 0 0
316 2099 7 10 113 94 16 2611 16
Animal Loss
9. A ladslide view of Balyalta from Patal villageA ladslide view of Balyalta from Patal village
10. Rehabilitation center in Balyalta and the landslideRehabilitation center in Balyalta and the landslide
SIBIR 2
11. A landslide crack developed on the side of the sibir,
How safe is the sibir??
12. Landslides in Guta Khola flowing SW to NELandslides in Guta Khola flowing SW to NE
Khaptad National park
13. SP Manandhar with the villagers observing rocks in GutaSP Manandhar with the villagers observing rocks in Guta
Khola and the landslide behindKhola and the landslide behind
14. A primary school of Guta village (A landslide is situated justA primary school of Guta village (A landslide is situated just
on the side of it)on the side of it)
15. Landslide in the upper part of the Argheli KholaLandslide in the upper part of the Argheli Khola
Argheli Khola
17. Children of Guta village in Rehabilitation centerChildren of Guta village in Rehabilitation center
18. A scarp of the displaced land >3m down part of the GutaA scarp of the displaced land >3m down part of the Guta
villagevillage
>3m
19. 1 man killed, 30 cattles (Cows and Buff) died, 10 cowshed
swept away by this landslide located near Guta villagelandslide located near Guta village
20. A landslide near Guta village facing towards northA landslide near Guta village facing towards north
41. Geology of the study area
1.Recent Deposit 2. Crystalline Complex
1.Recent Deposits;
Flood Plain Deposit: Consists of loose Colluvial sediments,
Boulders, cobbles, gravel, sand and
silt of granite schist and gneiss.
Colluvial Deposit: Consists of Boulder, fine to coarse
grained sand and silty sand
materials which are highly porous.
42. 2.Crystalline Complex: (Precambrian to Paleozoic)
a. Khaptad granite gneiss formation
Consists of coarse grained porphyroblastic granite, gneiss, augen
gneiss, migmatites and small bodies of granite, pegmatites and
Apilites.
b. Kachalo Khola Kyanite garnet mica schist
Consists of well foliated coarse grained kyanite bearing garnet mica
schist
c. Phulaut chloritic garnet mica schist formation
Consists of thinly bedded well foliated medium to coarse grained
chloritic garnet mica schist.
d. Buriganga Quartzo-feldspathic schist formation
Consists of coarse grained quartzo-feldpathic schist, gneiss, banded
gneiss, and augen gneiss with quartzite bands and chlorite mica schist
at places.
Contd. Geology of the study area
44. Methods
• Ilwis 3.3 as a software
• Bivariate statistical analysis approach
By C. J van westen (ITC, Netherlands)
• Preparation of factor maps:
Landslide distribution map
Geology map
Landuse map
Slope map
Aspect map
45. Methods Contd.
Crossing of Landslides map with the
corresponding factor maps
Calculation of Landslide densities
Calculation of Weight values
Creation of weight maps
Classification of weight maps
Creation of Landslide Hazard Zonation map
53. ResultsResults
• The Landslide Hazard Zonation Map is prepared.
• The study area specially the settlement areas lie in the high
landslide hazard zone, hence it is not safe for settlements.
• The Landslide disaster was caused due to the following
factors;
a. Excessive rainfall: The Nepalgunj station recorded
rainfall of 310 mm in 24 hours 26-27 August 2006. There
was continue rainfall for 72 hours in the affected area.
b. Landuse Practice: Rice cultivation with proper
canal facilities and over grazing of cattles in the
near by forest area are the main occupation of
the people in the area .
54. c. Geological conditions and steep slopes:
The area lies in the High Himalayan Crystalline zone
consisting of well foliated coarse grained Kyanite and
garnet bearing mica schist, granites and gneiss. The
mica schist is highly weathered. Geographically the
area is situated in steep slopes with an altitude range
of 1600 m to 1850 mmsl.
d. Toe Cutting:
The area consists of narrow and highly gradient
streams and the tributaries, due to which when there is
an excessive rainfall, water flows with high velocity
leading to toe cuttings along the sides of the streams.
Results Contd.Results Contd.
55. Results Contd.Results Contd.
The landslide hazard zonation
map is prepared using Ilwis 3.3
software and it shows that
nearly 39 percentage of the
study area is covered by high
hazard zone, 21 percentage is
covered by moderately hazard
zone and 40 percent of the area
is covered by low hazard zone.
56. ConclusionConclusion
The landslide disaster of 26 and 27th
August, 2006
took the lives of 7 people injuring 10 along with the
damage in property.
The geological and topographical conditions, Landuse
practices, excessive and long duration of rainfall and
toe cuttings were the main causes of landslide
disaster.
There are still many huge cracks developed in and
around the village area basically in the hill slopes. At
some places the ground subsidence has also occurred.
57. The people of the area are set up in the two
rehabilitation camps in the near by areas, one of which is
situated near the huge crack area and hence is under the
threats of landslide.
The area (Khaptad region) receives high rate of
precipitation every year. Very thick snow fall begins to
occur there from the month of October.
All the villages ( Balyalta, Guta, Putru, Bhedasen and
Tuka villages) are under the threats of further landslides
in the future, hence the region is not safe for the
settlement.
Contd. Conclusion
58. Most of the active and old landslides falls within
the high hazard zone indicating good reliability and
satisfactory precision of Bivariate-Statistical Model
in Landslide Hazard Zonation mapping.
It is found that About 94% of the landslides occurs
in High Hazard Zone, About 5 % of the landslides
occurs in Moderately hazard zone and the rest occurs in
Low Hazard Zone.
Contd. Conclusion
59. Recommendations
Rice cultivation and over grazing of the cattle in the
area should be discouraged.
Afforestation program should be carried out in the
barren slopes.
Proper drainage should be maintained for the seepage,
spring water and for the runoff water.
A detail study is essential regarding the stability of the
region.
60. Although many of the landslides can be minimized
by applying mitigation measures such as by using bio
engineering techniques, Retaining walls, Jute netting,
Gabion walls, French drains etc. In this case from the
economic point of view and its geographical
situation, it would be wise to relocate the people in
some other safe areas instead of trying to resettle them in
the same areas just by applying some mitigation
measures. It is essential to shift the people in the safe
areas before the coming Monsoon Season.
Recommendation Contd.
