A reconnaissance visit to the Laprak landslide in a remote portion of the Gorkha District, western Nepal.

1. Reconnaissance engineering geology
of the Laprak landslide,Gorhka
District, western Nepal
William C. Haneberg AEG 2008 Annual Meeting
New Orleans, Louisiana
Narayan Gurung

2. Acknowledgements
• AEG Foundation Research Fund
• Kadoorie Agricultural Aid
Assocation
• Dr. G.V. Ramana, Department of
Civil Engineering, IIT-Delhi
• The people of Laprak

3. Geologic setting
China
Laprak
Nepal
India
Source: Geological Map of Nepal (1994)
0 50 km

4. Walking to Laprak

5. View to the east

6. ?
View to the southwest across the Raizo Khola valley

7. Damage to an occupied home

8. More damage to another occupied home

9. Shaded Relief
Illumination from 30°/315°

10. Slope Angle
with Shaded Relief (30°/360°)

11. Slope Aspect
with Shaded Relief (30°/360°)

12. Foliation (335°-355°)
Shears? (300°-320°)
Joints (130°-140°)
Dip Direction (Aspect) of Known Planar Structures
with Shaded Relief (30°/360°)

13. Bedrock structural controls
Elevation
Easting
Northing

14. Bedrock structural controls
Metamorphic foliation
Elevation
Easting
Northing

15. Bedrock structural controls
Metamorphic foliation
Foliation-perpendicular joints
Elevation
Easting
Northing

16. Bedrock structural controls
Metamorphic foliation
Foliation-perpendicular joints
Low angle shears?
Elevation
Easting
Northing

17. Bedrock structural controls
Metamorphic foliation
Foliation-perpendicular joints
Low angle shears?
Easting
Northing
Colluvium wedges controlled by intersecting bedrock structures (upslope view)

18. Rainfall and landslide movement
1 life
10 homes 6 homes 5 homes 3 homes
12 hectares 5 hectares 4 hectares 2 hectares
5500
4125
Annual 2750
(mm)
1375
0
1500
Maximum 1125
monthly 750
(mm) 375
0
350.0
262.5
Maximum
daily 175.0
(mm) 87.5
0
1999 2000 2001 2002 2003 2004 2005 2006 2007

19. Laprak 1999 and 2007 extreme rainfall events
Gabet et al Himalayan rainfall threshold
• Compared peak sediment loads in streams with daily rainfall and annual
accumulated monsoon rainfall in the Annapurna region of Nepal
• Concluded that 850 mm accumulated monsoon rainfall was necessary for sediment-
generating landslides to occur each year
• Gabet et al, 2004, Geomorphology 63: 131-143

20. Remedial options
• Structural, grading, or drainage
• Hand labor, limited budget, difficult access
• Resettlement
• No suitable nearby locations
• Resistance to distant resettlement
• Warning system(s)
• Rainfall threshold
• Movement monitoring
• Temporary evacuation
• Safer buildings
• Lightweight materials
• Hand-buildable and affordable design?
• Resistant to landslides and earthquakes
• Easy to repair

21. Dhanyabat— Thank you