Detailed analysis of specific landslides affecting habitations, communication routes and civil projects in Northwestern Himalayas, Eastern Himalayas, Northeastern Region and Southern States including Nilgiris and Western Ghats. It involves identification of causative factors and formulation of treatment plans

UTTARANCHAL

A total of 343 landslide incidents studied, 150 debris slides and 193 rockslides.

HIMACHAL PRADESH

351 landslide incidences studied. Most of these were debris slides. These include the slides affecting areas like Dalhousie and Shimla towns and temple of Naina Devi.

JAMMU AND KASHMIR

• 84 incidences studied. Majority of these are located along the NH 1A and NH-1B.
• Inventory for 778 landslide incidences in NW Himalayas prepared.

• Uttarkashi town located at the toe of slips Varunavat Parvat on the right bank of Bhagirathi; covers 12 sq km area and inhabited by 16,000 people.
• Natural disasters faced by the town include floods in Bhagirathi in 1978, m=6.6 earthquake in 1991 and disastrous landslide in September-October in 2003.
• Massive landslide Varunavat Parvat started on September 24, 2003 following incessant rains in the area
• The slide debris buried a number of buildings having houses, hotels, government offices etc located near the toe of hill slopes.
• This affected 3,000 people and damaged property worth rupees 500 million.
• During August 2003 the geologists of GSI observed movement in slopes and advised district administration for evacuation of population from the toe area of the hill slopes. Prompt action by the district administration saved human lives when disaster struck the area.
• Causes identified include:
  • Saturation of overburden due to continuous heavy rain that led to development of pore pressure in overburden and underlying weathered quartzites.
  • The hill slopes were already vulnerable due to intense anthropogenic activity.

• Topographical mapping of slide area on 1:1000 scale
• Geological mapping on 1:1000 scale
• Geophysical surveys
• Characterisation of overburden mass
• Slope stability analysis, numerical modeling
• Monitoring of movement on slope by ATR
• Studies for biorestoration of overburden slopes

TREATMENT PLAN

• Grading of steep overburden slopes between EL 1660 m and 1800 m and provision of berms.
• Covering the resultant slopes with biodegradable geo-textiles that can support the growth of vegetation.
• Provision of geo-grid structures (retaining structures) at EL 1660 m to check the movement of loose mass.
• Provision of contour drains on rocky slopes between EL 1650 m and toe of hill slopes
• Provision of properly designed trunk of chute drains along the existing gullies and connecting these with contour drains
• Construction of main toe drain all along the toe of the hills. This is designed to debouch into the river Bhagirathi.
• Provisions of well-designed retaining structures all along the toe of hill.

EASTERN HIMALAYAS

SIKKIM

Detailed studies of landslides along

• NORTH SIKKIM HIGHWAY
  • Lanta Khola slide
  • Mayana Chu slide
  • B-2 slide
  • Rang rang slide
  • Mayang slide
  • Wong slide
  • Mauul slide

• NH-31A
  • Berrick slide
  • Lukubir slide
  • Depchajhora slide
  • KM-40 slide
  • KM-45 slide
  • Rangpo slide -1
  • Rangpo slide -2
  • Burdan slide
• DICKCHU - RONG RONG ROAD
  • Namok slide
• GANGTOK - NATHULA ROAD
  • Chandumari slide
  • 7th mile slide
  • 13th mile slide
• RUGSU-RANGLI ROAD
  • KM-16.4 slide
  • Sewakhola slide
• RONGLI PDAMCHEN ROAD
  • Kue Khola slide
  • Padamchen slide
• SINGTHAM-DIKCHU ROAD
  • Sinwani slide

WEST BENGAL

• DARJEELING AREA
  • Ambuta slide
  • Pagla Jhora slide
  • Giddapahar slide
  • Panchayat Jhora slide
  • 8.3 km slide on NH-31 A
    

• ASSAM
  • 20 km slide on NH-40 Silchar-Haflong road
  • Slides around Guwahati
• MIZORAM
  • Serchhip Hmar Veng slide
• MEGHALAYA
  • Dawki-Umlarem Road
  • Sonapur slide

SONAPUR LANDSLIDE

• At 142.5 km from Shillong on NH-44
• Crown located about 460 m above road and width is about 100 m
• Old slide got reactivated in 1988, in 1999 and again in 2001
• Heavy rains triggered the slide
• Probable causes of landslide include toe erosion, steep slopes, reduction of shear strength of slope forming material due to saturation
• Treatment measures suggested include training of nullah, protection of toe, grading of slopes, provision of surface drainage and vegetation cover over slope to reduce infiltration of water

SLIDES AROUND GUWAHATI URBAN AREA

• After 750 mm of rainfall over three days between 5th and 8th October 2004 many landslides occurred around Guwahati urban areas.
• These resulted in death of 17 persons and damaged property worth millions of rupees
• About 100 landslides of varying dimensions occurred along NH 44, Guwahati-Shillong road within a distance of 80 kms
• Causes responsible for slides include steep slopes, saturation of overburden on steep slopes and development of pore pressure due to heavy concentrated rainfall and encroachment on hill slopes
• Slope stability measures suggested include removal of civil structure from steep hill slopes, grading slopes and provision of vegetation cover to reduce infiltration of surface water into slope forming material, provision of retaining structure and creation of buffer zone between steep hill slopes and human settlements located at the toe of the slopes

MAO SONG SONG SLIDE ALONG NH 39, MANIPUR

• Located between 214.240 kms and 214.510 kms along NH 39
• Sinking of road 9.0 mts between July 11, 2004 and July 16, 2004 was observed
• Crown located at EL 1800 mt and toe at EL 1460 m
• Width of slide 300 m along road
• Overburden slide
• 80 houses inhabited by 130 families were damaged.
• Don Bosco School building moved 50-55 m horizontal
• Over saturation of over burden material due to incessant rains leading to reduction in shear strength of material resulted in multiple slides
• The treatment measures suggested include pushing of road towards hill side, sealing of cracks to minimize the infiltration of water into ground, provision of well-designed surface and sub-surface lined drains, grading of slopes, draining of accumulated water from pools on slope. The long term measure includes realignment of water channel

SOUTHERN STATES

• TAMIL NADU

• Landslide near Porthimund dam, Nilgiri district
• Monitoring of selected landslides in Nilgiris
• Study of slope failures in Kodayar, Kanyakumari district
• Marapalam landslide, Nilgiri district
• Landslide in Geddai, Nilgiri district
• Slope stability problem in Parali powerhouse area, Coimbatore district
• Landslide inventories in Nilgiri/preparation of Atlas
• ETA with reference to landslides in Kallarpallam reservoir area, Nilgiri district

• KERALA

• Landslide in Palakayam village, Palakkad district
• Landslide in Elachivali village, Pakakkad district
• Landslide in Kandalur Perumalai, Idukki district
• Mass movement studies in Palakkad, Palakkad district
• Landslide in Agamalavaran, Palakkad district
• Landslide in Kurusumala, Kottayam district
• Landslide in Amboori village, Tiruvananthapuram district

• KARNATAKA
  • 40 km long Skleshpur-Subrahmanaya road section of Hassan Mangalore railway line

• ANDHRA PRADESH
  • Last segment of Telugu-Ganga canal
  • Landslide at Somasila-Kandaleru flood flow canal, Nellore district
  • Landslides in Indrakeeladri hill, Vijaywada

WESTERN STATES

• MAHARASHTRA

• Nomaswadi hamlet, Kalse village, Sindhudurg district
• Nevhawadi hamlet, bhogve village, SE of Karill creek, Sindhudurg district
• Southern slope of nullah near Ghadrwadi, Baparde village, Sindhudurg district
• Thakurwadi, Kinjwadi village, Sindhudurg district
• Landslide on Sateri-Bhave temple road connecting Paralawadi and Gautamwadi near Malagaon village, Sindhudurg district
• Bramhanwadi of Pisekamte village, Sindhudurg district
• Manjuwadi Parule village Sindhudurg district
• Pune-Miraj section of Central Railways
• Landslide along Sayahadri-Ghat road sections
• GOA
  • Northwestern and western unstable slopes of Cabo hills