THREAT OF LANDSLIDES AND SEISMICITY IN SIKKIM HIMALAYAS

THREAT OF LANDSLIDES AND SEISMICITY IN SIKKIM HIMALAYAS

T. Tashi, Department of Mines, Minerals & Geology

Government of Sikkim, Gangtok-737101, Sikkim

Abstract

With a total geographical area of 7096 sq. kms., Sikkim is the smallest amongst the North-eastern Council States. It lies between 27⁰00’46” – 28⁰07’48” North Latitude and 88⁰00’58” – 88⁰55’25” East Longitude and has elevation range of 250m to 8598m above main sea level. The State’s increasing population and developmental activities and depleting land and natural resources are in a collision course. Seismic and landslide vulnerability hazard compounds the evolving scenario. Government initiatives are in place to counter and mitigate the existing and perceived negative side effects. Their efficacy is yet to be proved.

INTRODUCTION

The common sight of high relief, swathes of verdant forest, raging fast flowing rivers and rivulets, steep slopes that are under failing and failed conditions, high seismicity and so on characterize the mountain ecosystem of the Sikkim Himalaya. Considering the fragility, diversity and complexity of the existing geoenvironmental settings and the ecosystem, manipulation of natural constants either by nature or man in an unsustainable manner can lead to irrepairable short as well as long term negative side effects and devastation.

The Sikkim Himalaya has never been and will never be free from ubiquity of weak geology, slope instability, frequent seismicity, soil erosion etc. mainly due to natural causes and partly as a result of accelerated degradation. These adverse conditions in tandem can exacerbate the existing fragile, vulnerable and multi-functional mountain ecosystem. So far disasters caused by landslides, earthquakes, floods etc. have not lead to large scale human tragedy in Sikkim in recent memory. However, there is ever increasing human demand of natural resources, especially land for urban development and mega dams in an apparently unsustainable manner, making some of the denizens to adapt and survive at dangerous margins. The emerging crisis can perhaps be minimized by indigenous knowledge based and modern technological interventions. To safeguard against accelerated degradation and improve the living standards of the hill people, the Governments (Centre and State) need to address hill specific issues through systematic and effective integration of the ecosystem services and development, highland and lowland linkages etc. Without a replicable

and hill specific developmental policy, the ever present threat from devastating landslides, earthquake, floods etc. remains and the options and the opportunities of the progeny in jeopardy. A beginning has been made by the State of Sikkim by asking the Department of Science & Technology (DST), Government of India to undertake systematic study of landslide problems in the State. The DST accordingly prepared a status report on landslides in Sikkim. Based on the report, the DST, Government of India, is considering establishment of a multi-disciplinary cell dedicated to landslide studies, not only in Sikkim but the entire Northeastern states. Such a initiative has become imperative because past experience shows that different agencies carry out landslide studies at will and without coordination with each other. Results of such exercises never actually got disseminated and proved futile. Whereas the seismicity monitoring is concerned, site response studies using digital accelrograms located at seven-station-strong motion network in Sikkim by year 2000 and twelve-station network by year 2006 has been done by IIT, Kharagpur and study results are widely published.

GEOLOGY AND TECTONICS

Mallet (1875) & Bose (1891) were the first explorers who gave an account of geology and mineral resources of Sikkim Himalaya. Subsequent explorations by Auden (1935), Heim and Gansser (1939), Ray (1947) Ghosh (1952), Raina & Bhattacharya (1975), Raina and Srivastava (1980), Thakur (1986), Ravikant (1993), Neogi et al (1989), Ray (2000) and others gave important and valuable contributions towards understanding of geology of Sikkim.

The current literature describes geology of Sikkim similar to that of the Eastern Himalaya where four distinct geomorphology based transverse zones or tectonostratigraphic domains, separated by major tectonic dislocations, are identifiable. Out of these four tectonostratigraphic units, namely; Sub-Himalaya, Lesser Himalaya, Higher Himalaya and the Tethys Himalaya, the Phanerozoic rocks of the Sub-Himalaya are not exposed in Sikkim. The Lesser, Higher and Tethys Himalaya of Sikkim are typically arranged in a domal shape or arch of thrust surfaces in the form of culmination across Teesta river, popularly known as Teesta culmination (Mcclay, 1992, Ray, 2000). The core of the Teesta culmination is occupied by Proterozoic Lesser Himalaya low grade metapelites of Daling Group of rocks. The distal part is made up of medium to high-grade Proterozoic Higher Himalaya crystalline complex, the Main Central Thrust (MCT) separates the Lesser and Higher Himalaya. Gondovana (Carboniferous to Permian) and Buxa Group of rocks are exposed in the Rangit window zone, small window near Rorathang, East Sikkim and as thrust/fault slices in South Sikkim. The Tethys Himalaya is represented by Cambrian to Eocene fossiliferous sediments of the North Sikkim Tethyan zone which tectonically overlie the Higher Crystalline Complex (see map).

REGIONAL SEISMICITY

The tectonic frame work and the seismicity of the northern eastern states including Sikkim are considered as a result of collision tectonics in the Himalayan arc and subduction tectonics below the Myanmarese arc. Studies have indicated a very complex tectonic setting of the region due to constant movement of the Indian plate from South to North & Myanmarese from East to West.

The two major structural elements in the Eastern Himalaya are the Main Central Thrust (MCT) and the Main Boundary Thrust (MBT). The Foot Hill Thrust (FHT)/Main Frontal Thrust (MFT) along the Southern edge of the Himalayan bring the Siwaliks in Juxta-position with the thick recent sediments of the Indo-gangetic plain. There are also a large number of prominent lineaments in this region, some of which are reported to extend for several kilometers beneath the Himalayan Foredeep. The Teesta lineaments which pass through Parbatipur area of Bangladesh to Bhadrapur area of Nepal, is considered to demarcate the Western limit of Eastern Himalayan seismicity.

The North Eastern India was subjected to severe shaking by a number of damaging earthquakes. The systematic account of which is available from the middle of nineteenth century only. Besides the Cachar earthquake of 10^th January 1869 (Magnitude 7.5), the twenty other severe earthquakes exceeding magnitude of seven and affecting the region during the past hundred years have been tabulated (Ramchandran et al, 1981). Among the recorded earthquakes, the most damaging ones and macroseismically studied are the great Assam Earthquake of 12^th June 1897 (M=8.7), Srimangal Earthquake of July 8, 1918 (M=7.1), Dhurbi Earthquake of July 3, 1930 (M=7.1), Assam Earthquake of August 15, 1950 (M=8.6), Assam Earthquake of July 8, 1975 (M=6.7), Cachar Earthquake of December 3, 1984 (M=5.4), Manipur-Burma Earthquake of August 6, 1988 (M=7.3), Assam-Tripura Earthquake of April 13, 1989 (M=5.7) and Manipur Earthquake of January 10, 1990 (M=5.4).

In the Eastern Himalayas, the seismicity is considered as a result of collision tectonics & correlated with the MBF and MCT (Gupta S.K. 2003). The MCT is shown passing through Gangtok to Mangan and then to lower Tolung to north of Sada from where it cuts through North

of Labdang-Tashiding to Gyalshing and then to Kaluk to Soreng before coming out of Sikkim border at an area where it meets the MBF (India-Nepal border).

The IIT, Kharagpur has carried out site response studies using strong motion network of accelerographs in Sikkim during the past ten years. The findings are available in the form of a paper with site response contour maps (Nath, et al 2000) and a paper with microzonation maps (Nath, et al 2006).

The existing record shows (Table 1) that the state has been subjected to local earthquakes of M=5.0 to M=6.5 and non-local high magnitude earthquakes of above M=8.0 (1897 and 1950 of Assam), (1934 of Bihar). The whole of the State is therefore, has been slotted in Seismic Zone IV of IS:1893-1984 and categorized as High Damage Risk Zone of MSK VIII.

Considering the seismically vulnerability of the State all new constructions are subjected to strict observance of BIS codes or seismic codes. The existing unsafe and non-engineered building stock still remains and is practically impossible to address the entire such building stock. The alternative left is to retrofit only the life line buildings such as hospitals, schools, cinema halls, multi-storied hostel/apartments etc.

LANDSLIDES

Mass wasting processes are a universal phenomina in mountain, hill and hilly areas of the world. Their magnitude, frequency and type differ from place to place and on the material that is undergoing displacement either through chemical or mechanical means. In the Himalayas, mass wasting process is dominated by landslides. The magnitude, intensity and frequency of Himalayan

landslides vary from East to West and from South to North. The variation is controlled, mainly by climate, neo-tectonism and seismicity. The eastern Himalaya including Sikkim is a hot-spot for natural hazards, particularly landslides and earthquakes.

Landslides of all types and size occur in almost all types of rocks and quaternary formations of Sikkim. The Daling Group of rocks, especially, Gorubathan Formation appears more prone to landslides than the inhomogeneous quaternary deposits and gneisses and schists of Higher Himalaya. The high landslide susceptibility of the Daling Group of rocks has been attributed to their severe shear distortion due to loading and unloading during orogenesis, higher rate of weathering and mineral composition. A cursory survey of frequency of occurrence of landslides in Sikkim was done in 1991 and the result clearly showed that the East and South Districts where Daling rocks dominate are affected by maximum number of landslides (Table below)

DISTRICT	VERY SEVERE	SEVERE	MODERATE	TOTAL
North	32	NA	NA	32
South	90	148	130	368
East	5*	9*	3*	153
West	40	16	33	89
	167	173	166	642

(* only prominent ones)

Almost all the landslides in Sikkim occur after prolonged exposure to monsoon rains and occasionally during or just after cloudbursts or precipitation intensity exceeding 135-145 mm in 24

hours. The red letter month of October 1968 was considered the most disastrous month in recent years of Sikkim history. On 5^th September 1995 heavy rain triggered off a mud avalanche near Gangtok killing 32 people. Similarly, non-stop heavy rain since early June 1997 damaged 300 houses completely, 1000 houses partially and caused death of 51 people in East and North districts of the State. Rain, therefore, has been one of the main triggers besides weak geology, steep slopes with thick overburden, frequent earthquakes etc., causing landslides.

There has never been a systematic study of landslide problems in Sikkim. Most of the existing literature on landslides of Sikkim are written by some fancy expert expatriate on a whirlwind visit to the State. Since no two landslides are identical in any given area, it is not always easy to know the ground realities of mechanism to trigger off landslides. The State Department of Mines, Minerals & Geology, took up a number of landslide prone and affected areas for systematic study and mitigation measures. Besides treating some chronic rotational type of landslides along State highways with slope dressing, benching, installation of effective drainage systems and so on, some planar type slides, controlled by joint, foliation and bedding planes were further subjected to grouting and rock bolting, both tensioned and untensioned (see pics). The notoriety of a landslide is known by its maximum capacity to cause damage to life and property. Some of the well known landslides falling in that category are as shown in Table 2. Sikkim being a land locked State, disruption of road communication by landslides is an annual affair. For every linear kilometer of Sikkimese road there are atleast 10 minor to major slips.

Tensioned Rock Bolting

Tensioned Rock Bolting

CONCLUSION

Natural hazardous events such as earthquakes, landslides, floods etc. in the Himalayas are a reality. Man and man-made structures stand no chance against the awesome power and fury of such events when they strike. Therefore, a mechanism is needed to safeguard against massive and unwarranted loss of life and property in the event of a calamity. In August 2004, the Government of India came out with a detailed status report on Disaster Management in India. The report specifies various programmes and strategies of the Nation to tackle and mitigate all forms of destructive natural events. Translation of some of the recommendations have already begun in Sikkim. The Department of Land Revenue & Disaster Management, Government of Sikkim and UNDP has undertaken various initiatives in this direction. The general public is sensitized through awareness training/talk shows, mock drills, banners and so on. The North eastern states including Sikkim being in high seismogenic domain, landslide and flood prone areas require special attention and constant vigilance. The on-going research by established institutions in various fields of adverse events needs up-gradation and monitoring by an apex authority for proper and effective coordination of long term research and dissemination of information to stake holders. The existing scenario of haphazard and secretive study of natural events by all sorts of agencies needs to be discouraged.

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About Mr Tshering Tashi :-

Mr Tshering Tashi is a 55 yr old geologist who is Director (Dept. Of Mines, Minerals & Geology) Govt. of Sikkim. After completing his school in Tashi Namgyal Academy, Gangtok, he went onto do his M.Sc,(Applied Geology)from IIT, Kharagpur and M.S. (Geology) from Univ. of Colorado(USA).

I know him personally and when he is not immersed in work he is a fun loving person who loves fishing or just relaxing with his family.

praful rao

A shameful saga (RTI ignored)

___________________________________

I had submitted an application to the State Public Information Officer, Office of the District Magistrate on 19Aug2008 (under the Right to Information Act 2005) seeking certain information as regards Disaster Management in the Darjeeling District. After taking up the issue with the State and National Information Commissions and after the State Commission served them a show cause notice (see blogs of 06Dec08 and 01Jan09), I was finally faxed a reply to my RTI application,almost 5 months after I filed my questionnaire (Copy of FAX is reproduced above as EXHIBIT 1)
I have reproduced the questions which I asked and the replies (in red Italics)recd below:-

The reply to my RTI application makes a mockery of both Disaster Management and the RTI Act2005. Undoubtedly we will be pursuing this issue further.
_____________________________________________________

To,
The SPIO,
Office of the District Magistrate,
Darjeeling Date : 19Aug2008

Application under Right to Information Act 2005

Kindly provide the following information with respect to landslide hazard prevention and mitigation in Darjeeling District:-

1) Was a survey carried out by the District Disaster Management Authority (DDMA) to determine the exact extent of damage due to landslides and identify high risk areas in Darjeeling district following the exceptionally heavy rainfall in the first week of Sep2007?
If “YES”, please furnish details and findings
If “No”, please give reasons.

No, DDMA was formed in this district till date. But survey on landslide areas in Kalimpong Sub-Division
was held several times.

2) Please furnish details of any landslide prevention work done in high risk populated areas (such as Alaichikhop, Dr Graham’s dispensary area in Kalimpong and Harsing, Lebong in Darjeeling and Baggaora in Kurseong)after Sep07 to mitigate/prevent any landslide that might occur ( this work would essentially have been short term fire-fighting measures such as jhora training / drainage repair etc).

Will be sent later on

3) Please furnish details of landslide prevention and mitigation work carried out in Darjeeling district in the last 5 years.

Will be sent later on

4) Please specify for the last 5 years:-
a) Total fund allocation for Disaster Management in West Bengal.
b) Fund allocation to Darjeeling district for this purpose.
c) Amount spent on landslide prevention and mitigation.
d) Areas where major landslide prevention work was carried along with expense details and year when the
work was carried out.

a), b), c), d) under process


e) Details of landslide awareness programs carried out in the district by the DDMA.

Awareness programme relating to landslide was scheduled to be held by State Disaster Management Authority on 27.11.08. But due to unavoidable circumstances the programme could not be held.

5) Please furnish details of your short/ mid/ and long term plans regarding landslide hazard prevention and mitigations in the district in the future.

Landslide prevention work will be done by the respective departments as per G.O. No 128 PR dated 16.1.08 (copy enclosed) and this has been informed to all concerned vide this office Memo No. 121/DMS dated 28.3.08

I am depositing Rs10/- as application fee.

________________________________

praful rao

The way forward - An update on planned STH activities

a) Dr RK Bhandari {former Chairman/ founder of Centre of Disaster Mitigation and Management (CDMM), Vellore Institute of Technology and perhaps the foremost expert on landslides in the country} who has been a strident supporter and also adviser of STH has been contacted. He has asked STH to get in touch with CSIR (Council of Scientific & Industrial Research) and Ministry of Earth Sciences and send them a letter of STH activities and ask for help (for awareness programs etc). He said he would also put in a word for STH with these agencies.

b) Shri KM Singh, Member NDMA who is in charge of the National Disaster Response Force (NDRF) in the NDMA has been contacted. He said he would help regarding, a) Printing publicity material as regards landslide hazards thru NDRF resources. b) Sending NDRF personnel to participate in awareness programs as regards medical first response in landslide disasters.

c) The Director of Cinchona plantations (Dr Gyan Subba) in this region has been contacted. When we talked to him, he was most aware and positive about STH activities and asked me to include the Cinchona plantations in the awareness workshops...he would extend whatever help was possible.

d) Mr Amit Khasnawi is the Officer in Charge Civil Defence, in Kalimpong, and he contacted us sometime ago regarding STH. As we all know the civil defence plays a major role in all rescue operations in a post disaster scenario. STH (Kalimpong) has a meeting with him today to find out how our activities can be integrated with those of the Civil Defence.

e) Dr Sanjay Rana (North Bengal Univ), Dr Subir Sarkar (Head of Dept, Geography - North Bengal Univ), Dr Varun Joshi (Head of Dept, Disaster Management- GB Pant Institute, Gangtok and Mr Manav Prasad, Commander, 764 BRTF, Mr Tsering Tashi, Director Mines, Sikkim have all been contacted in the last few days with a request for articles as well as advice, support, inputs for STH activities. All were very positive.
Besides this ,Mr Trilok Kr Dewan (IAS), former Chief Secretary Andhra Pradesh, now a resident of Darjeeling, has also talked to concerned officials in Delhi regarding the landslide problem in these hills.

f) Mr Suman Rai of ATREE (Eastern Himalayas) has always been an ardent supporter of STH activities. We have invited him over tomorrow for a meeting with STH (Kalimpong). He has kindly agreed.

praful rao

The light at the end of the Tunnel?

Further to the earlier post dated 06Dec2008 on the RTI application.
I had asked some questions way back in Aug2008 (SLIDE 1) regarding landslide prevention measures in the district....
questions to which I have yet to receive answers despite the West Bengal Information Commission having intervened in Oct2008 (SLIDE 2) and directed the State Public Information Officer (SPIO) at the District Magistrate's office in Darjeeling to answer the relevant queries "within 15 days".
Two days ago I received a copy of the show cause issued by the State Commission to the SPIO, Office of DM Darjeeling (SLIDE 3) on 18Dec2008... the deadline ie "within 7 days of receipt of this letter" is again long passed, nevertheless I see a light at the end of the tunnel.
The press coverage in the Telegraph is reproduced below :-
_____________________________________

Info glare on officer

RAJEEV RAVIDAS

Kalimpong, Dec. 31: The West Bengal Information Commission has showcaused a public information officer for failing to provide disaster management-related information to Save The Hills (STH), an NGO. In its notice dated December 18, the commission has asked the state public information officer of the disaster management authority, posted in Darjeeling, to explain within seven days from the receipt of the letter why he has failed to respond to the queries of Praful Rao, the president of STH. It has also threatened to impose penalty on the officer according to the provisions of the the Right to Information (RTI) Act. Under Section 20 of the act, the failure to comply with an RTI request can lead to a fine of Rs 25,000 as well as disciplinary action. The Kalimpong-based organisation, through an application under the RTI Act on August 19, had sought to know the long and short-term measures contemplated by the district disaster management authority to mitigate landslide hazards in the district. The NGO had also wanted to know whether or not most landslide-prone areas had been identified and the money allocated and spent on disaster management in the district. Rao said he was compelled to approach the state commission after the district authorities failed to respond within the stipulated one-month period. “Hopefully, something positive will emerge from the commission’s notice,” he said. Describing the RTI Act as an effective tool to extract information from the government, Rao said STH’s experience had shown that it was almost difficult to get it on time. “The RTI Act stipulates a time limit of 30 days for questions to be answered, but even after more than four months of submitting the application, we are yet to get any response,” Rao said. The NGO was formed after landslides caused severe damage in the hills in September last year. When contacted, the information officer, Biswanath Barik, said: “We have received the notice. We will respond to it in the next three-four days.” __________________ Comment by praful rao My thanks to Mr NP Dixit, President Citizen's Right Forum, Kalimpong for having written to the State Commission on behalf of STH

A letter from a Friend

I received this email today from Prof Leszek Starkel (above), of the Polish Academy of Sciences, Krakow, Poland - who was our Main Speaker and Resource person in the Landslide Hazard Workshop organized by STH in Southfield College, Darjeeling on the 21Nov2008.
STH is proud to be associated with the likes of Prof Starkel, who is one of the world's foremost scientists in Geomorphology.
_______________________________
Dear Mr Rao,

Ten days ago after coming back to Poland I returned to annual reports, editorial work etc and two events turned my mind again to last workshop in Darjeeling and to our Himalaya.On Monday I got your letter and at the Cracov University (one of the oldest in Central Europe), I attended the ceremony of awarding the Dalai Lama by the highest degree of Doctor Honoris Causa.
I like to thank you for invitation and excellent organisation of seminar on landslide. The initiative of Save the Hills is very important and should be extended. In my opinion most of presented papers should be published including also panel discussion. Parallel to that it would be useful to publish more popular book with many figures and photos showing causes and effects of extreme events, scale of damages and ways of protection. Such book should be delivered to all schools, tea
gardens etc.

I wish you and all members of Save the Hills
Merry Christmas and Happy New Year


Yours

Leszek Starkel

_____________________________

Comment by praful rao
My thanks again to all those who contributed their time and resources towards making the Landslide Hazard Workshop at Darjeeling "excellent".

How to corrupt a noble system..

The RTI Act 2005 is one of the most progressive pieces of legislation in our democracy because it empowers the ordinary citizen to question the Govt and the powers that be.
Unfortunately, even this Act which stipulates a time limit of 30 days for questions to be answered has been corrupted...
I had put an application under the RTI Act2005 on 19Aug2008 (SLIDE 1), asking for certain information regarding landslide prevention and fund utilization from the SPIO, Office of the District Magistrate, Darjeeling. Receiving no reply within the time frame assigned I sought the intervention of the West Bengal State Information commission - they did intervene sending this letter, dated 22 Oct2008 (SLIDE 2).
Since the district admin paid no heed to the State Information Commission, I have taken the matter up with Central Information Commission (Slide 3&4) on 05Dec2008... what ought to have taken one month has already taken the better part of three and a half months and I have still not received the answers to my questions!

praful rao

The ATREE workshop at Darjeeling

Two days workshop held

By DT Correspondent on November 28,2008

Darjeeling, Nov 26: A two day seminar held by ATREE ( Asoka Trust for Research and Ecology) brought a league of researchers, scientists, bio-conservationists and NGO workers under one roof to discuss a rather impending issue that seems to loom about the atmosphere. The conservation of bio-diversity and the sustainable usage of the forest was the sensitive issue being floored in the seminar. The group had representatives from South India ATREE Branch, representatives from the North East and Darjeeling Branch as well.

Detailed presentations were made on issues such as reconciling conservation with livelihood, monitoring the ecological conditions of the forest and drivers of ecosystem change, cultural ecology and link to conversation, livelihood strategies of forest dependent communities in Western Ghats, community ownership to sustain natural resource based enterprise, Conservation Education at ATREE on the first day by the team from South India.

On the second day the team from North East and Darjeeling made their presentations on the conservation of the flora and fauna in and around Darjeeling, how to encourage conservation of forest and also encourage people to tap into the resources of nature but in a sustainable way, so as to generate a source of income in these communities. Mr. Suman Rai ATREE Darjeeling talked about how to build working relations, networking and collaboration in such a way that it is beneficial to both parties involved through his personal experience.

Mr. Praful Rao made a rather startling presentation about landslides, which is a great danger to the hills. The presentation was really powerful as it showed real places we know and live in. DLR Prerna also presented it’s progress it is making in the communities it is working, in form of fair trade of tea, fruits. Management of the premium generated from the trade of these products. Also research it conducts to develop environmentally friendly agriculture practices. Mr. Amba Jamir from Nagaland gave an interesting presentation on shifting cultivation, also in a very positive light.

An environmentally charged seminar, where a lot of serious issues were discussed in a very interactive way. There was a constant dialog between the two teams who also sheared their personal experience, also suggesting solution for problems that seem to be persisting in an area though the way they have handled the problem. It was a forum where a lot of knowledge was exchanged from people who have had experience first hand in the field

Ava Rai, DT Correspondent, Darjeeling

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Comment by praful rao

As I have repeatedly emphasized in all the presentations I have made - it is good to have these workshops and awareness camps but ultimately they must translate into action on the ground ie our drainage systems will have to be revamped, an aggressive afforestation program must start and so on...

Objectives of SaveTheHills

Objectives of STH

1. To work towards prevention , mitigation and management of landslides hazards in the Darjeeling and Sikkim Himalayas.
   
   
2. To develop and enhance public and govt awareness of the causes, effects of landslides through all means possible and thereby reduce disaster risk through hazard awareness.
   
   
3. To conceive of and implement capacity building measures to the extent possible in order to make the community more resilient to landslide disasters.
   
   
4. To monitor/report and visit landslide areas so as to create a database on landslides in the Darjeeling and Sikkim Himalayas (with the possible causes of landslides).
   
   
5. To monitor rainfall through satellite based reports and other means so as to alert communities of the threat of possible landslides.
   
   
6. To liaise with GSI and other scientific agencies during surveys so as to provide assistance and accurate local knowledge inputs.
   
   
7. To network with other NGOs and govt agencies so as to increase knowledge about landslides and earthquakes.
   
   
8. To participate in and organize workshops with a view to enhance disaster education about landslides and earthquakes.
   
   
9. To participate in relief, rehabilitation and reconstruction work to the extent possible after landslides/earthquakes.
   
   
   praful rao
   

"Landslides for dummies" by Dr Malay Mukul

We all know that the Himalaya has been formed by the collision of the Indian and the Eurasian plates and this process has been going on for the last 50 million years. The process of mountain building on our planet is accompanied by earthquakes and building of “topography” or relief resulting in formation of slopes. Once the slopes are built beyond a certain critical angle (that largely depends on how weak or strong the material or rocks/soils that make up the slope are) they strive to reach equilibrium by collapsing under the forces of gravity. This is essentially the landslide process that we encounter. Slopes can fail and slide at lower angles if the binding vegetation is removed or fluids get into the system. In an active mountain belt like the Himalaya, landslides are, therefore, an inherent product of mountain building where slopes are built to the point where they are no longer stable and then collapse to reach an equilibrium state. Landslides are, therefore, part of a natural process and we cannot stop or arrest this process no matter how hard we try. Our only option to avoid landslides completely is to move out of the hills and go to the plains. However, that is not a solution we seek at this juncture. So the next option we have is to try and understand the natural processes that lead to landslides so that we don’t facilitate them and develop an understanding of the risks involved in living on hill-slopes. To understand landslides an understanding of the geology of the region (preferably at the scale of our towns, villages etc.) should be the first order of business. While the detailed geology of the Darjeeling-Sikkim Himalaya is still in the process of being worked out, first-order features are more-or-less understood. First, there is almost a cake-like layering of rocks in Darjeeling-Sikkim Himalaya; the rocks are mechanically stronger as you climb up to the top of the cake. For example, rocks in the Teesta valley are weaker near the river than rocks higher up on mountain tops like Ghoom, Darjiling or even Delo. The Teesta has simply cut through this layering like a knife. Also, the layers in this cake are separated by particularly “weak” zones termed as faults which are basically large fractures which can be seen exposed on the surface but run deep underground. In these zones, the rocks have been crushed and powdered by natural processes and consequently they typically end up forming thick soils over the years. You cannot blast your way to solid rocks in fault zones. Needless to say, these are also zones that will slide easily and are difficult to stabilize. A typical example of this is the Birrik slide zone on NH-31A which has been active for decades now. A landslide in a fault zone is something which you cannot do much and the best strategy is to get the hell-out-of-the-way. Such zones have to be carefully identified and mapped at a scale of the habitat being planned. For example, in the Kalimpong area we have weaker rocks in the southern part of town and stronger rocks in the northern part of town (e. g. at Delo). So the fault zone separating the two layers of rocks must pass somewhere in between. This zone needs to be clearly identified and mapped in detail because this zone might hold the key to landslides around the Kalimpong area. This study is lacking at present. I fear that this zone might be heavily urbanized. While we cannot really do much to correct the presence of this geological zone, we can at least be careful to secure and stabilize it and keep out of this zone to the extent possible. Similar studies need to be carried out in the towns of Kurseong and Darjeeling and urban centres of Sikkim.

The bottom line is that as long as we live in the Himalaya, landslides will be part of our lives. We need to accept this and plan for it to the extent possible. Identification of geologically weak zones as well us having mitigation strategies in place would be the way to go. We cannot be thinking that all is well and adopt an ostrich mentality. We are not only vulnerable to landslides but also to large earthquakes and the worst case scenario would be a double whammy of both these hazards hitting us together. Great earthquakes cause multiple landslides as was evident in Kashmir during the recent earthquake. Unfortunately, we have chosen to ignore traditional wisdom and take backward steps in rapidly urbanizing our hills with concrete multi-storied dwellings. There will be a price to pay when the next big earthquake coupled with seismically induced landslides strikes the hills of Darjeeling and Sikkim. We know that for a fact from the Kashmir earthquake. The best we can do now is to minimize that price by acknowledging that we have a problem and taking remedial steps to the best of our ability.

Yes! We are living in a geologically precarious zone. We need to really map this zone in detail to begin with. Map the old and existing landslides closely next. Correlate the two and see what we get and have our mitigation strategies in place accordingly. That would be the strategy I would recommend. There are studies and reports on the entire Darjeeling-Sikkim area but that will not serve this purpose. We need very detailed work here specific to the urban area under consideration. It would also need to be done by a team of geologists, geographers and engineers who should be able to slant their specializations towards landslide hazard determination and mitigation. The work should be carried out in close consultation by social activists like you so that the deliverables can be directly used for policy making.

Personally, I think the best way to go about it would be to approach some Govt agency (like NDMA) for funding, get a team of motivated and qualified people together and start working on it ourselves rather than waiting for people to help us.

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About Dr Malay Mukul

Dr Malay Mukul is perhaps the only scientist and geologist in CSIR Centre for Mathematical Modeling and Computer Simulation, at Bangalore who is fond of quoting John Lennon!
He did his Ph.D from Rochester University (USA) but much before that he did his schooling from Dr Graham’s Homes, Kalimpong, hence his intimate knowledge of this area. Malay who is the recipient of numerous awards and has published many papers and books, is still a frequent visitor to Kalimpong where his parents are settled.
For more on Dr Mukul please visit this link (http://www.cmmacs.ernet.in/~mlym/index.html)

In the above letter sent to me by Malay, the title and italics are mine

praful rao

Images from the Landslide Hazard Workshop at Darjeeling on 21Nov2008

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Comment by praful rao

My thanks to Anubhav Sood of St Joseph's College, North Point, Darjeeling and Hemkar Rana (ex - member STH, Kalimpong) for the photographs.