Natural Hazards Assessment in the Everest Region Natural Hazards Assessment in the Everest Region using Hydrodynamic and Geo-Spatial Tools using Hydrodynamic and Geo-Spatial Tools Birendra Bajracharya bbajracharya@icimod.org GIS Specialist International Centre for Integrated Mountain Development (ICIMOD) 28 March 2006, Islamabad, Pakistan
The Everest Region The Everest Region
A DSS Framework for Ecosystem Management A DSS Framework for Ecosystem Management Land units Land system for ecosystem territorial management External Internal Pressure Impact Aquatic Terrestrial driver class driver class class class system system Energy Anthropic system Tourism system Waste Pastoral system Subsistence economy Stone extraction Timber/ firewood extraction Agricultural system Natural system GLOF hazard Infrastructure Landslides Agriculture land Avalanche Forest land
Mapping Natural Hazards for DSS Mapping Natural Hazards for DSS • Modeling GLOF and simulation • Modeling GLOF and simulation • Inventory and distribution of landslides • Inventory and distribution of landslides • Hazard Mapping • Hazard Mapping
Why are the Mountains Hazardous? Why are the Mountains Hazardous? • Fragile geological conditions • Fragile geological conditions • Great elevation differences • Great elevation differences • Steep sloping terrain • Steep sloping terrain
Glaciers and Glacial Lakes Glaciers and Glacial Lakes • Sources of the headwaters of many great rivers • Glacial lakes are formed by accumulation of water from the melting of snow and ice cover and by blockage of end moraines • Sudden break of a moraine may generate the discharge of large volumes of water and debris causing floods (GLOFs) After the severe impact of the 1985 Dig Tsho GLOF, glacial lakes and the GLOF phenomenon in the Nepal Himalayas drew great attention
Glacial Lake Outburst Flood (GLOF) Glacial Lake Outburst Flood (GLOF) Dig Tsho (Langmoche) Glacial Lake burst on 4 August Birds-eye view showing the remnants of Dig Birds-eye view showing the remnants of Dig Dig Tsho (Langmoche) Glacial Lake burst on 4 August 1985, destroying the nearly completed Namche Tsho Glacial Lake, Langmoche Glacier at the Tsho Glacial Lake, Langmoche Glacier at the 1985, destroying the nearly completed Namche Hydropower Plant (estimated loss of US $1.5 million), 14 slope and the debris along the gully after the slope and the debris along the gully after the Hydropower Plant (estimated loss of US $1.5 million), 14 bridges, trails, cultivated land and loss of many lives. GLOF of 1985 (WECS 1991) GLOF of 1985 (WECS 1991) bridges, trails, cultivated land and loss of many lives.
Inventory of glaciers, glacial lakes and GLOF Inventory of glaciers, glacial lakes and GLOF Dudh Koshi Basin 278 Glaciers (482.2 sq. Km) 473 Glacial lakes (13.07 sq. Km) 9 Potentially dangerous lakes (Lumding Tsho, Dig Tsho, Chokarma Cho, Imja Tsho, Tam Pokhari, Hungu Lake, East Hungu 1, East Hungu 2, and West Chamjang)
Potentially dangerous Potentially dangerous lakes Everest region lakes Everest region Three potentially dangerous lakes identified in the Everest region – Dig Tsho, Imja and Lumding Tsho
Growth of Imja and Growth of Imja and Digtsho Digtsho Imja: Based on 2001 data (Yamada) Area = 0.83 Km 2 Avg. depth = 41m Max. depth = 90 m Water volume = 35.8 million m 3 Increase in area between 1991-2001 = 0.23 Km 2 Dig Tsho: Area in 1962 = 0.2 Km 2 in 1983 = 0.6 Km 2 (before outburst) in 2001 = 0.35 km 2
Imja Glacier Imja Glacier 15 December 1962 Corona 15 December 1962 Corona
Imja Glacier and Glacial Lake Imja Glacier and Glacial Lake 02 December 1983 Space Shuttle 02 December 1983 Space Shuttle
Imja Glacier and Glacial Lake Imja Glacier and Glacial Lake 19 March 2001 IRS 1D Pan 19 March 2001 IRS 1D Pan
Imja Glacier and Glacial Lake Imja Glacier and Glacial Lake 29 November 2001 IKONOS Multispectral 29 November 2001 IKONOS Multispectral
IKONOS image draped over DEM IKONOS image draped over DEM
Field Photo, April 2005 (Arun Shrestha) Field Photo, April 2005 (Arun Shrestha)
Field Photo (Arun Shrestha) Field Photo (Arun Shrestha)
Topographic Information Hydro-dynamic modeling of GLOF Hydro-dynamic modeling of GLOF • Topographic Information (DEM) • Topographic Information (DEM) • Extraction of geometric and Hydraulic Information • Extraction of geometric and Hydraulic Information (HEC GeoRAS) (HEC GeoRAS)
Bathymetry of Imja Bathymetry of Imja
Topographic Information Input Input Parameters/Input Data Values for GLOF Unit Simulation parameters parameters Dig Tsho Imja km 2 Lake surface area 0.4 0.86 Lake maximum depth 42.9 90 m Dam top elevation 4395 5030 masl Dam bottom elevation 4360 4960 masl Dam outside slope 1:0.47 1:8 Dam outside slope 1:1.7 1:6 Dam width 210 600 m Dam length 600 650 m kg/m 2 Unit Weight 2000 2000 Porosity 0.4 0.4 Manning's n of outer core 0.15 0.15 Internal Friction Angle (ø) 34 34 Cohesiveness 0 0
Topographic Information Modeling GLOF Modeling GLOF • Dam Breach (NWS-BREACH) • Dam Breach (NWS-BREACH)
Topographic Information Modeling GLOF Modeling GLOF • Dam Breach model outputs • Dam Breach model outputs Breach Output Unit Dig Tsho Imja Maximum Outflow (Q max ) m 3 /s 5613 5463 Duration of the Outflow (T out ) hr 2.0 3.2 Initial Water Level masl 4395.0 5030.6 Final Water Level masl 4373.6 4982.3 Final Depth of the Breach m 35.0 65.2 Final Width of the Top of the m 231.0 30.5 Breach
Topographic Information Modeling GLOF Modeling GLOF • Flood Routing • Flood Routing 10.00 9 Imja Dig Tsho 9.00 8 8.00 7 Flood Depth (m) Flood Depth (m) 7.00 6 6.00 5 5.00 4 4.00 3 3.00 2.00 2 0 10 20 30 40 50 0 5 10 15 20 25 30 35 40 Distance from Lake (Km) Distance from Lake (Km)
Topographic Information Modeling GLOF Modeling GLOF • Flood Routing • Flood Routing
Topographic Information Modeling GLOF Modeling GLOF • Comparison of model and observed values (Dig Tsho) • Comparison of model and observed values (Dig Tsho)
Topographic Information If Imja Breaks… If Imja Breaks… Simulation of GLOF scenario from Imja Simulation of GLOF scenario from Imja
Topographic Information If Imja Breaks… If Imja Breaks… Simulation of GLOF scenario from Imja Simulation of GLOF scenario from Imja
Topographic Information If Imja Breaks… If Imja Breaks… GLOF vulnerability at Dinboche GLOF vulnerability at Dinboche
Flood arrival time (Imja) Flood arrival time (Imja) Discharge (m 3 /s) Place Time(min) Flood Depth(m) Imja lake outlet 0.00 5458.00 Dhumsum 6.00 5419.00 3.92 Dinboche 8.40 5401.00 5.81 Chure 10.80 5387.00 8.12 Orse 12.00 5382.00 5.77 Panboche 14.40 5374.00 6.76 Confluence 22.80 5329.00 8.68 Bengkar 25.20 5316.00 9.29 Gumela 26.40 5315.00 8.47 Thulo Gumela 27.60 5310.00 7.76 Sano Gumela 28.80 5304.00 8.01 Ghat 30.00 5297.00 8.13 Nakchung 33.60 5275.00 5.71
Flood arrival time (Dig Tsho) Flood arrival time (Dig Tsho) Place Time(min) Discharge (cumec) Flood Depth(m) Dig Tsho outlet 0.0 5610.00 6.17 Langmucha 4.80 4986.00 4.19 Kamthuwa 9.00 3592.00 5.32 Hungmo 13.20 3300.00 4.58 Thyangmoche 17.40 3100.00 3.74 Thame 21.60 2897.00 5.42 Power House 21.60 2888.00 4.89 Pare 21.60 2835.00 4.97 Confluence 30.00 2577.00 5.49 Nakchung 60.60 2145.00 5.16
Landslide Hazard Zonation Landslide Hazard Zonation • Landslide Inventory • Landslide Distribution • Slope Stability Analysis
Landslide Inventory and Distribution Landslide Inventory and Distribution • Topographic Maps (1:50000) • Satellite Images (IKONOS, 2001) • Aerial Photographs (Stereo Interpretation)
Landslide Inventory and Distribution Landslide Inventory and Distribution • Satellite Images (IKONOS, 2001)
Landslide Inventory and Distribution Landslide Inventory and Distribution • Topographic Maps (1:50000)
Landslide Inventory and Distribution Landslide Inventory and Distribution • Aerial Photographs (Stereo Interpretation)
Landslide Inventory and Distribution Landslide Inventory and Distribution Serial No Field Name 1 LandslideID 2 Type of Material 3 Type of Movement 4 Vegetation Condition 5 Slide Activity 6 Estimated From 7 Hydro Condition 8 Slide Occur In 9 Contributing Factor 10 Landslide Depth 11 Landslide Body 12 Slope Form & Aspect 13 Slide Material Type (Lithology) 14 Weathering Condition 15 Latitude 16 Longitude 17 Average Length 18 Average Width 19 Area
Slope Instability Hazard Slope Instability Hazard Criteria Lithology Slope Land cover Moraine Everest Meta Sediments < 18.5 < 33 < Snow Black Gneisses Water Himalayan Gneisses < 20.8 < 42.5 < Migmatic Ortho Gneisses Bare soil Augen Gneisses < 24.4 < 42.2 < Rocks Leuco-Granite < 21.8 <42 <
Slope Instability Hazard Slope Instability Hazard Lithology • Compiled from literature review and existing data sources
Slope Instability Hazard Slope Instability Hazard Slope • Derived from DEM
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