- Landslide at TNEB Colony, Emerald, Nilgiri District, Tamil Nadu (06th August, 2020)
A landslide (earth-flow) occurred near the TNEB colony, Emerald, Kundah Taluk, Nilgiri district, Tamil Nadu, after a spell of heavy rainfall of about 34.6 cm (for the period ending 24 hrs. on 7th August 2020). As a result, four houses were damaged due to the debris flow. However, many small-scale landslips were also recorded in the area. The slide (Lat: 11°19'14.94"N and Lon: 76°37'31.34"E) is a complex slide, which initiated as a cut slope failure and the subsequently leading to the earth flow. Ground cracks ranging from 5-10 cm were observed in the close vicinity of the slide, which also indicates chances of future reactivation, if untreated. Ground subsidence of about 1 m was observed in the slide zone.
- Landslide at Talacauvery, Bhagamandala, Kodagu District, Karnataka (06th August, 2020)
The landslide in Talacauvery has occurred on 06th August, 2020 at at 02:30 am, on a day of heavy rain, near Talacauvery Temple on Brahmagiri hills near Bhagamandala in Kodagu district, Karnataka along the approach road to the temple. Talacauvery, the place from where Cauvery River originates is an important pilgrim and tourist centre. The area is situated 43.5 km east of Madikeri town. It is a reactivated slide and it was first initiated during the year 2007. The present slide got reactivated on 06th August, 2020 due to intense rainfall covering part of the old slide zone (2007). It can be inferred that the Talacauvery landslide underwent four episodes of events i.e. on the year 2007, 2018, 2019 and 2020.
- Landslide at Pettimudi, near Munnar, Idukki District, Kerala (06th August, 2020)
A landslide occurred at Pettimudi, near Munnar, Idukki district, Kerala on 06th August, 2020 around 22:30hrs, due to heavy and incessant rainfall. As a result, four housing lines of tea garden workers (layams) of Kannan Devan Hill Plantations (KDHP) situated at the foot slope area of Rajamala Hill ranges, got buried under debris (more than 80 people lived). There were 66 casualties reported. The landslide (Lat: 10°10'18.10"N and Lon: 77° 0'40.70"E) initiated as shallow planar at rock-overburden contact and the distressed material was directed through the topographic hollow scouring entire material from both the flanks and flow path. It is inferred that the failure must have occurred / initiated at the head of a steep gulley / streamlet.
- Landslide in and around Longmai-Khumji Noney Area, Noney District, Manipur (June-July, 2020)
The Longmai landslide (Lat: 24°51â19.3âN and Lon: 93°37â26.5âE) occurred during the last week of June, 2020, along the upslope of the NH-37, the Imphal- Jiribam road about 500 meters from Noney Bazar towards Imphal. The landslide occurred at the eastern flank (hill slope of 45° toward 130° at sliding zone) of NNE-SSW trending hill ridge. Cracks in the concrete house, the paved drain and the approached road are observed. It caused subsidence of 40 cm in the crown portion of the slide and 60 cm in the highway. Five number of houses were partially damaged due to this slide. The Khumji Noney Slide (Lat: 24°5â45.7âN and Lon: 93°37â26.6âE) occurred about 100 meters from Noney bazaar towards Jiribam on the NH-37, Imphal-Jiribam road. The area is represented by highly dissected, rugged, NNE-SSW trending alternate synclinal hill ridges and anticlinal valleys showing a 2nd order topography. Excessive cutting of the slope for construction of waiting shed and water seepage in the upslope portion are the geo-scientific causes.
- Landslide around Mao Town, Senapati District, Manipur (July, 2020)
The Mao landslide (Lat: 25°30â57.3âN and Lon: 94°08â11.5âE) has affected an area of about 0.6 sq.km. posing immense risk to the critical road infrastructure and affecting the residential and commercial buildings along the NH-2 due to the development of tensional cracks and subsidence of the road bench. The present landslide affected area is part of the old-landslide zone, with thick unconsolidated/ semi consolidated debris above the in-situ bedrock. The landslide affected area has a very poor surface drainage management. During heavy rainfall during the month of June and July 2020, water flows over the road and remain stagnant within the depressions caused due to heavy vehicle movement with stagnant water along the road side-line concrete drainage. The transient downward water percolation on the road, steep and moderate steep slope, where the surface material is old-landslide debris has lead to the over-saturation of the underlying material.
- Landslide at Tigdo Village, Papumpare District, Arunachal Pradesh (10th July, 2020)
A landslide occurred at Tigdo Village under Doimukh circle, Papumpare district, at around 2:30 am on 10.07.2020, due to heavy rain. As a result of the landslide, a house was totally damaged and 4 persons of a family buried and causes loss of property. The main causative factor is the continuous heavy rainfall resulting in subsurface percolation of rainwater and the build-up of undesirable pore pressure in overburden material. Anthropogenic activities, such as deforestation and high angle slope cutting, is also considered to be a causative factor.
- Landslide at Donyi Colony, Papumpare District, Arunachal Pradesh (25th June, 2020)
A landslide occurred at Donyi Colony, Itanagar, Papumpare district, Arunachal Pradesh, at around 8:12 am on 25.06.2020. The landslide (Lat: 27â° 04'52.7"N and Lon: 93â° 36' 46.2"E) is initiated due to the outward and downward movement of unstable slope material resulting into loss of life (a two-year-old child) and property. The main causative factor is attributed to the incessant heavy rainfall over the last few days which oversaturated the unconsolidated slope forming material of the Quaternary Period composed mostly of sand, silt and clay. Infiltration of the rainwater resulted in the development of pore water pressure and reduced shear strength parameters of the slope forming material, thereby causing the slope failure. Moreover, anthropogenic activities, such as deforestation and unplanned house and road construction practice also contributed to the slope instability.
- Landslide at Cachar, Hailakandi and Karimganj District, Assam (June, 2020)
In the first week of June 2020, several parts of Barak Valley comprising three districts of Assam viz., Cachar, Hailakandi and Karimganj were affected by eight (08) nos. of landslides triggered by incessant and heavy rainfall. The landslides are spread over four (04) Toposheets: two landslides, viz. Govindanagar Slide and Kanakpur Slide in Cachar District, falling in Toposheets No. 83 D/14 and 83 H/1 respectively; four landslides viz. Mohanpur Grant Slide 1, Mohanpur Grant Slide 2, Mohanpur Grant Slide 3 and Chandipur Slide in Hailakandi District falling in Toposheet No. 83 D/10; two landslides in Karimganj District, viz. Karimpur Slide 1 and Karimpur Slide 2, falling in Toposheets No. 83 D/5. Incessant and heavy rainfall from 24.05.2020 caused over-saturation of overburden material and led to rapid down slope movement of material along the cut slope faces.
- Landslide at Jowai, Kabi Village, West Jaintia Hills District, Meghalaya (26 May, 2020)
Eight numbers of landslides of varying dimensions has occurred on 26th May 2020 at different localities within the Jowai Township affecting the residential areas, as a result of the incessant rainfall in the preceding days. The primary triggering factor of the documented landslides is heavy antecedent rainfall which increased surface runoff beyond the drainage capacity of existing drainage system in the affected areas. No rockslide was documented during the investigation. The soil/debris in the affected slopes was super-saturated which increased the shear stress component leading to the failure.
- Landslide at Dhare & Sitala, Kabi Village, North Sikkim District, Sikkim (24 May, 2020)
Two landslides occurred one each at Dhare and Sitala area, on 24th May 2020, 04 km away from Kabi Village towards Gangtok on North Sikkim Highway (NH 310A). The coordinates of the Dhare landslide (Lat: 27° 23â² 55.2â³N and Lon: 88° 37â² 24.9â³E) and Sitala landslide (Lat: 27° 23â² 54.2â³N and Lon: 88° 37â² 32.4â³E) and falls in SOI Toposheet No. 78A/11. At both the landslide locations, it has been observed that the area mainly comprises of unconsolidated soil and debris material. No in-situ rock was observed in and around the area. These two landslides are located in close proximity of a NE-SW trending Regional Fault which is the major cause of concern. Excessive water saturation due to improper irrigation practice (Cardamom) cultivation reduces shear strength parameters of slope forming materials and makes slope prone to failure. Toe erosion by unplanned cutting of road section, as observed at both Dharey and Satala area, may also result in slope failure.
- Landslide at Kabi Village, North Sikkim District, Sikkim (24 May, 2020)
A landslide got reactivated on 24th May 2020, near upper Kabi Village area on the state highway, adjacent to the border between East and North Sikkim Districts of Sikkim, causing disruption of traffic. The location is about 22 km from Gangtok on Gangtok- Mangan North Sikkim Highway via Phodong. The coordinates of this landslide are Lat: 27° 23â² 35â³N and Lon: 88° 38â² 7â³E and falls in SOI Toposheet No. 78A/11. The landslide is characterized by wedge failure along with falling of bedrock material along a steep slope (>70°), due to the action of gravity and flow of water through weak planes, which resulted in the accumulation of huge amount of rock debris.
- Landslide at Mawlai-Umjapung, East Khasi Hills District, Meghalaya (21 May, 2020)
A landslide occurred at Mawlai-Umjapung about 50 m East of NH-40 on 21st May 2020 around 1:00 pm. It was reported that the landslide had partially buried a house (Lat: 25° 37â 12â N, Lon: 91° 52â 57.8â E), when a retaining wall collapsed after incessant rainfall. About 20 m x 15 m area on the gently dipping slope has been affected by the slide. A poorly constructed retaining wall collapsed onto a house destroying it into debris. A family of five people have been rendered homeless. The slope, modified for settlement is composed of a thick overburden of highly oxidised cohesive clayey soil. Incessant and heavy rainfall has led to increase in pore water pressure on the weak retaining wall besides static load due to settlement above the failed portion resulted into the failure.
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