The Landslides of September end (20-23Sep) 2020

The above rainfall followed the formation of a LOW pressure area in Bay of Bengal around the 20Sep

21Sep2020 images

In the morning, we had a report in 'Hazard Alerts' our WA gp of extremely heavy rainfall on NH 10 and very soon this image of the flooded bridge (Coordinates 26.9832971E 088.417920N) at RAMBI (Kalimpong) was also posted.👇
Rambi was a small, sleepy town known mostly for the local mushroom production till recently- the construction of a dam (TLDP III) and the IRCON Sevoke-Rangpo Broad Gauge railway tunnel work have added prominence to the place.

Almost simultaneously reports of Mirik (Darjeeling district) experiencing torrential downpours came in and this image showing an ☝ area of Mirik town (coordinates 26.8853° N, 88.1828° E) near the lake was posted. It resembles a flooded place in the plains.

22Sep2020 images

Damage on National Highway (NH)10

SETI Jhora landslide (Coordinates 26.93946N 088.44148E, Elvn 233m)

This ☝ gaping hole on NH10 was due to toe erosion by the Teesta river on 23Sep2020 at Seti Jhora . This spot has always been a major maintenance challenge on NH10 and has been responsible for several fatalities in the recent past.

Sign diverting highway traffic put up at Teesta after landslides blocked the NH10 at 29th mile 👇 on 22Sep2020.

29Mile Landslide (Coordinates 27.01435N 088.43594E, Elvn275m)

The scene was in fact worse in the plains of North Bengal 👇 as can be seen in the image from Cooch Behar (26.323921N89.451088E)

My thanks to all those who contributed the photos, reports etc via WhatsApp and in our group (Hazard Alerts) for us to maintain a record of the event for posterity,

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya

A picture which is our shame : a spring in Kalimpong

 As is known, springs all over the Himalayas are fast drying up and I have been involved in several attempts to rejuvenate springs in Kalimpong in the past (see 1 and 2).
It is therefore shocking to see the condition of many of springs from which so many draw their drinking water, this is just one example.

Praful Rao,
Kalimpong district
Darjeeling Sikkim Himalayas

Landslide Report 3 (Kalimpong) - Sep2020

Continuing with the landslide surveys (See Report 1 and Report 2 in this blog)  around Kalimpong town, on 09Sep2020, we went to the north eastern sector of Kalimpong along Reshi Road upto ALGARAH. This road is of strategic importance to India since much of the logistics for the Indian army in East Sikkim (opposite Doklam) goes thru this road. Also in case of NH10 being blocked, this road, via Lava/Gorubathan serves as the alternate route to Siliguri.
Regarding the survey:

• Besides the landslide/subsidence zones mentioned below, what was very evident was the serious deterioration in the condition of the Kalimpong -Algarah section of Reshi road with numerous sinking areas visible on many parts of the road, where another heavy shower or two could result in collapse of the road at multiple places.
• What should be also noted here is that the entire region has many natural springs and jhoras which during heavy rain causes a lot of erosion and landslides in the area.
  
• STH has recorded the extreme rainfall events of AUGUST 2020 and their effects in earlier posts (see 1 and 2). Further the rainfall of August 2020 is also available in this blog. All the landslides recorded below were the result rainfall during the extreme rainfall events.
  

GHATEY KHOLA subsidence

Coordinates: 27° 4'42.00"N, 88°29'50.88"E
Size of subsidence of road : approx 45m in length
During periods of intense rain, Ghatey Khola is notorious for causing landslides in this area since the runoff from the entire populated areas at the crest of the hill finds its way into this drain.
14th Mile sinking zones
The 14th mile sinking areas have been featured in this blog numerous times (see 1 and 2) and are one of the oldest landslide zones in Kalimpong. During the heavy rains of August 2020, these areas were re-activated at almost the same locations causing large portions of the Kalimpong- Algarah road (Reshi Road) to subside.
No other damage to farmland or infrastructure was observed.

Sinking areas of Algarah town

Algarah town is approx 15 kms NE of Kalimpong and has a long history of landslides. I had visited the area some years ago and marked out the sinking areas (above). WIth less rainfall in the past few years, the landslide and sinking zones had also diminished. This year with the intense rains that we have had, the hotspots have re-emerged and perhaps the most crucial one is the one in LAMA WARD which is located in the centre of Algarah town.

Coordinates: 27.1172° N, 88.5837° E
Landslide at HART spring, Dr Graham's Homes, Kalimpong

Coordinates: 27° 4'56.22"N, 88°29'48.48"E 

Photo credits: Ms Shreya Gurung

Praful Rao,
Kalimpong district
Darjeeling- Sikkim Himalaya

Rainfall data of some towns in the Darjeeling- Sikkim Himalaya - AUGUST 2020

 Surprisingly:

• Darjeeling town had less rain than Kalimpong town.
  
• Sikkim rainfall (all 4 districts) was much less than that of Kalimpong and Darjeeling.
  

The New Normal : Intense bursts of rain in overnight thundershowers

Graphs from AWS of SaveTheHills show the pattern of rainfall at Kalimpong on 05/06Aug2020 and 26/27Aug2020. In both cases, thundershowers commenced in the late evening or night and got over within a couple of hours with instantaneous rainfall intensities going upto 252mm/hr on 05Aug.

Did we have a cloud burst on 05Aug2020?
Even though we cannot prove it, I do believe we had one. Rainfall intensities reached never before levels of 252mm/hr and the event caused major damage to roads in Kalimpong and infrastructure in W Sikkim.

And it is not as if we have not had cloudbursts earlier

STH has already recorded the extreme rainfall events of AUGUST 2020 and their effects in earlier posts (see 1 and 2).

My thanks to Ms Shreya Gurung for compiling the rainfall data.

Praful Rao
Kalimpong district
Darjeeling-Sikkim HImalaya