Yes, agricultural terrace induced landslide is what is meant by ATIL and you have heard it right.
Idea might sound insane but then, backed by experience, common sense, insight and intuition, it shouldn’t be way far off the bullseye.
Having witnessed ATIL caused devastation way back in 1998, it was hard to believe then that it would take disastrous proportions in just a few decades.
It was ATIL that caused large scale devastation in the Mandakini valley in August 1998, and with changed ground realities the risk has increased by manifold, and at present it poses major threat to most hilly terrain of the province.
With footfall in Mandakini valley increased by manifold, is it not time to evaluate the risk and do something to mitigate it?
Mandakini valley
Contrary to literal meaning of its name – one that flows calmly – the water of Mandakini river is highly turbulent particularly in the upper reaches, and one can only speculate if it ever flows calmly.
Close to its origin at Chorabari glacier is located Kedarnath shrine that is highly revered by Hindus, and the valley is studded with a number of other attractions that include shrines of Kartik Swami, Kalimath, Basu Kedar, Trijuginarayan, Onkareshwar, Madhyamaheshwar, and Vishwanath, as also Deoria Tal and Vasuki Tal.
Mandakini valley is therefore visited by tourists and pilgrims in large numbers, and the trend of the present year clearly shows that the footfall in the valley, unlike previous years, has exceeded that of Badrinath.
Credit of this should certainly be shared with Prime Minister Narendra Modi ji who took keen interest in Kedarnath re-development, and actually acted as brand ambassador not only of the shrine but also of the province.
Turning from tourism to disaster risk – human congregation in the geologically fragile valley housing a mountain torrent is sure to enhance risks of various kind, and many of you would attribute this to be the main cause of June 2013 disaster in the Mandakini valley.
Database and assessment
But then, 1998 tragedy and causes thereof – AITL or anything else – shouldn’t be secret. These would have been studied, analysed and debated in various forums. Moreover, we are expected to learn lessons from previous disasters, and take appropriate actions to bring forth resilience, aren’t we?
Assessing risk and acting to reduce it thus hold the key to building resilience.
Out here, it is important to note that our behaviour or actions are a function of our risk perception – assessed individually and often instantaneously based on memory, accumulated knowledge and experience, or institutionally using databases, complex algorithms and data crunching devices.
To be accurate, this requires us to remember or have record of previous disasters with exact details of the vulnerability functions. We do many a times claim to remember or have record of all previous disaster incidences, and the same is the basis of all hazard and risk assessments done by us.
One needs to understand and accept that we don’t generally remember finer details of incidences unless exposed personally to these. It is particularly so with regard to mishaps and disasters – thanks to fading affect bias.
Moreover we have no institutional mechanism for objectively recording disaster losses with associated vulnerability functions. So the disaster induced loss data you are exposed to frequently could be way off the bullseye, and both our risk perception and risk assessment outcomes could thus be distorted.
Having said so, does anyone remember details of the tragedy that took place in the Mandakini valley, not in 2013 but in 1998?
Mandakini valley disaster of 1998
In the year 1998, two main tributaries of Mandakini – Kaliganga and Madhyamaheshwar were devastated by landslides, and the human death toll in these incidences stood at 101.
Most devastation in these valleys took place on 11-12 August, 1998 with the area receiving around 300 mm rainfall in the first 10 days of August. The lush green valley was thus scarred deeply by the slides, and significant proportion of the agricultural land was lost together with 62 human lives. Most of these slides initiated from agricultural terraces on steeper slopes of the valley, and the rolling down debris took devastating proportions.
This was a clear case of ATIL.
As if devastation of the valley by ATIL was not enough, a massive landslide near Bheti village on 18-19 August, 1998 blocked the course of Madhyamaheshwar river forming a lake, and there was panic in the downstream areas along Alaknanda river that had suffered previously in 1970 due to landslide lake outburst floods.
Fortunately, the lake breached naturally after 24 hours and the threat was diffused.
Bheti landslide
Large portion of the hill slope with moderately good forest cover around Bheti village slipped down on 18-19 August, 1998 ravaging three habitations – Bheti, Pondar and Sem.
According to the locals a major ground fissure running parallel to the valley had come into existence in the forest area above Bheti village after 1991 Uttarkashi Earthquake, and the same registered significant widening some days prior to the landslide.
Geomorphic changes: It was interesting to note that the debris generated in the Bheti landslide on the left bank of Madhyamaheshwar river glided upslope on the opposite bank overrunning Pondar and Sem villages.
Bheti landslide pushed the death toll to 101 as also changed geomorphic setup of the surrounding area; the agricultural lands and habitations were replaced with heaps of boulders and debris, and two streams that once fed Madhyamaheshwar disappeared amid the landslide debris.
Geological observations: Three prominent joint sets were observed in the rocks hosting the Bheti landslide, and water percolating through these provided favourable conditions for movement along the dominant and pre-existing weak plane whose trace was observed as ground fissure in the forest above the Bheti village.
There were incessant rains for weeks before the incidence, and the pore water pressure crossed the threshold. Water gushing out in the middle and lower slopes at many places together with the seepages in the scrap of the Bheti slide testify this fact.
Water thus lubricated the weak planes, while saturation of soil and other unconsolidated material resting on the hill slope increased the magnitude of the forces trying to destabilise and bring down the material.
Toe erosion by Madhyamaheshwar river on the fateful day only destabilised the slope, and triggered movement along the pre-existing weak plane.
ATIL in Mandakini valley
Spatial distribution of August 1998 landslides in the Mandakini valley correlated positively with the agricultural terraces, particularly those falling under high slope category.
Population pressure had perhaps compelled masses to undertake cultivation on slopes that were traditionally considered unfit for agriculture. Compulsion of bringing more land under cultivation at the same time forced people to increase the height of the retaining walls of these agricultural terraces.
Combined together – terraces with high retaining walls on steep slope – it was a perfect recipe for slope instability. Water impounded in these terraces due to prolonged rains further added to this instability.
Moreover, water getting accumulated in the agricultural terraces soon started to flow downslope. This flow of water laden with soil of the agricultural terraces rapidly eroded the downslope areas and soon transformed into major slides.
This type of slope instability arising from the agricultural terraces or ATIL, and resulting gully erosion and landslides were prominently observed between Bedula and Rau-Lek in Madhyamaheshwar valley and between Bedula and Kalimath in Kaliganga valley.
Destabilised terraces and landslides
Both erosion potential and transportation capacity of the flowing water are a function of its density and velocity.
During heavy rainfall incidences that are not uncommon in the region, damaged retaining walls of the agricultural terraces yield to the force of water accumulating in the terraces and flowing downhill. This water assimilates the soil of the agricultural terraces and moves downslope as a soil laden high density flow.
This high density flow moves downhill at a high speed, and carries along everything that comes in its way – vegetation, boulders and rock mass – and soon creates deep gullies and turns into a massive landslide.
This is what happened in August 1998 between Bedula and Rau-Lek in Madhyamaheshwar valley and between Bedula and Kalimath in Kaliganga valley. These are however not the sole examples and at present significant area in the hill districts of the province faces the threat of AITL.
Changed ground realities
Except for Bheti most landslides in both Madhyamaheshwar and Kaliganga valleys in August 1998 initiated from the agricultural terraces. It can thus be safety concluded that ATIL was the main cause of 1998 Mandakini valley disaster.
It is however important to note that way back in 1998 agriculture was the mainstay of the economy of the region, and migration was not that rampant. Agricultural terraces were therefore regularly and keenly maintained and repaired at that time.
Under changed ground realities wherein large number of people have migrated from the villages, appreciable proportion of hitherto cultivated agricultural terraces lay barren.
Most people of the Mandakini valley no doubt return home regularly, particularly during the Kedarnath Yatra period. Rather than indulging in agricultural pursuits, most returnees however engage in more lucrative and rewarding Yatra related affairs.
So at present, with mountain agriculture pushed to the corner due to various reasons including migration, there is literally no one around even to cultivate these agricultural terraces leave apart regularly mending and maintaining them. Large proportion of agricultural terraces thus lay barren with their retaining walls weakened and damaged by natural denudational forces with the passage of time.
Soil and other unconsolidated materials thus rest behind the damaged retaining walls of these terraces in a precarious condition. It is therefore no surprise that this material often starts to flow under the impact of heavy rainfall incidences resulting in ATIL.
This problem is not restricted to Mandakini valley alone and migration that is rampant in all the hill districts of the province has transformed large proportion of agricultural terraces into barren tracts that are vulnerable to ATIL.
Increased ATIL risk
Even though we started with Mandakini valley, entire Uttarakhand is faced with similar situation and the problem is sure to take gigantic proportions, if not tackled effectively and timely.
Most agricultural terraces, particularly on the middle slopes of the hill, are located at the site of previously active landslides that provide suitable conditions for soil formation. Though stabilised with the passage of time, geomorphic conditions making these sites vulnerable to slope instability have not changed much, and if exposed to external forces these could get reactivated.
This type of landslides initiating from the agricultural terraces or ATIL could result in large scale destabilisation of the hill slopes and make the region chronically prone to landslides.
Moreover, climate scientists have long been putting forth warnings of increased frequency and intensity of extreme climate incidences. To us it means more frequent spells of intense rainfall or cloudburst, and prolonged dry spells. These would further enhance the risk of ATIL by manifold.
Moreover once the long dormant slide zones housing agricultural terraces are reactivated, undertaking stabilisation and treatment works is going to be challenging, both financially and technically. We are all aware of the progress made in the treatment of Balia Nala landslide that threatens the lake city and is being monitored by the High Court.
ATIL is thus to aggravate the problem of landslides in the region by manifold and pose a serious threat to the viability of various ongoing infrastructure projects in the region.
AITL would thus initiate a vicious cycle wherein both people and investment would move out of landslide infested hills of the province, and this in turn would leave little incentive for either state or individuals to invest in mitigation and prevention, implying more AITL incidences which would further enhance pace of withdrawal of people and investment – hence poor, deserted and undeveloped hills.
I am sure no one really wants this grim scenario.
Mitigation strategy for ATIL
In order to tackle ATIL effectively, it is primarily required to recognise and better understand this slope destabilising process through in depth research and studies. This is however a long term proposition, and mitigation works cannot be delayed for want of that.
The problem having been identified and seriousness of the issue understood, it is necessary that timely action be initiated to ensure stability of the hill slopes.
Since the root cause of the problem lies in weakened retaining walls of the agricultural terraces, logical and simple solution of ATIL lies in ensuring regular and timely maintenance and repair.
To begin with, areas that have habitation, infrastructure and others in the downslope side of the agricultural terraces can be taken up for maintenance.
We started with Mandakini valley that has a number of trekking routes, and very high footfall. The valley could therefore be the right candidate to pilot this project. Barren agricultural terraces upslope of trekking routes and en route halts should therefore be identified, and taken up for maintenance and repair.
Moreover, there is no dearth of finances for undertaking this task as the state at present has State Disaster Mitigation Fund (SDMF) at its disposal.
Community involvement for sustainability and development
Community involvement and participation is key to the success of most projects and programs. Moreover, the target being gigantic and time lapsing fast, success is likely to be illusive without involvement and participation of the masses.
Awareness has been known to be the key to mass mobilisation and therefore – seriousness and implications of the problem, together with suggested solutions and schemes formulated for implementation have to be communicated aggressively to the masses in bold and capital but in simple language – not lacing it with unnecessary data and scientific jargons.
Moreover, designing the awareness drive with an appeal to the little tradition and ancestral heritage of the masses could really do wonders.
Though depopulating fast, large number of people still live in the villages in the hills and carry out limited agricultural operations in their fields. Due to low returns from farm output in the hills and nonavailability of resources they however have little incentive to invest on the regular maintenance and upkeep of their agricultural terraces.
Soft loan and subsidy, together with support for crop diversification and marketing could be an incentive for these people to take better care of their agricultural terraces. This could easily be done through various ongoing schemes of agriculture and horticulture departments.
The provision of repair and restoration of damaged retaining walls of the agricultural terraces can also be done through Mahatma Gandhi NREGA.
At the same time an effective appeal to little tradition and ancestral heritage of the people could motivate some migrants to make an effort to rejuvenate and maintain their ancestral house as also agricultural terraces. This group could even be ready to share the cost of regular maintenance and upkeep.
Providing custody of these maintained fields to ones still undertaking agricultural activities would add to their prosperity, while entrepreneurs can be roped in for organising homestay ventures in the houses of migrants, on profit sharing basis through related schemes of tourism department.
These measures would ensure community involvement in this innovative scheme, and at the same time give boost to the economy of the region, provide much needed gainful employment opportunities and check the pace of migration besides reducing the burden of state exchequer and keeping the region safe from the wrath of recurring landslides.
Moreover this would save the soil that is a major resource, and takes long time to get replenished.
Other returns apart, 10 paisa spent on this is sure to save resources worth many rupees in times to come. So the investment is worth making as the dividends are real high.
Dear Piyoosh,
I could sense a little confusion regarding the agricultural terraces and the landslides from your write-up and therefore wish to make some points those might clear this doubt.
1. We all know that in the mountainous areas the exposed rockface gets degraded / decomposed constantly under the prevailing climatic and environmental conditions at the given place those help in loosening the constituents of the mass and consequently keeps it failing/ moving down the slope in the form of colluvial debris (slope wash + lithic fragments). On availability of gentler, flat or trough like topography on the mountain slope between the top and the valley floor (dictated largely by bedrock underneath) such debris deposits may form periodic solifluction lobes stacking over the slopes. The spread and thickness of these solifluction lobes depend on the loose mass generated in the upslope area and precipitation period cum intensity that would flush that down.
2. The large agricultural terraces those we witness on the mountain slopes are transformed from these failed slope debris deposits and therefore the agricultural terraces are not inducing landslides (ATIL) but are products of landslide itself. The shallow non-engineered retaining walls/raisers around the different lobes or terraces are constructed just to retain the top soil. Because the debris deposit/ material makes a highly assorted and unconsolidated mass with large cavities/ voids within, a differential settlement forces the terraces to undergo subsidence and retaining wall collapse.
3. The debris resting on the mountain slopes as mentioned above, normally remain unstable except for some places where subsurface rock structure or topography provides trough like form, and therefore subjected to further slope failure depending on two important engineering properties like cohesion and angle of internal friction at a given point. Therefore, any major infrastructure project through these deposits should be avoided. One must understand that any deadload or extra load on the slope would worsen the slope instability and therefore to counter that de-loading is advised. Also, afforestation over such slopes should be avoided because it would facilitate large infiltration of surface water. Plz. remember, more than 90% landslides in the Himalayas are in debris/ soil slopes and failures in such slopes are saturation related. Therefore, checking surface water to infiltrate ground would prevent or reduce the chances of failure. The unused/ barren terraces considerably seal the surface and prevent the rainwater to infiltrate and thereby reduces the landsliding.
Most of the staircase agri-terraces are non-rbm terraces – the palaeo-debris aprons and highly permeable hence, comparitively unstable and prone to movements. With scaricity of arable agri lands in mountainous tracts, anthropogenic stress on such “vulnerable debris aprons” has increased adding accentuating the risk of movement. I beleive the watershed management deptts. may have developed some solutions on this high priority societal-need and if not, it’s not late enough to start doing it.
Good one. Yes terrace cultivation on steep slopes cause immense damage during sudden heavy downpours and I have experienced it in Himachal too
Very easy to understand explanation of ATIL . Thanks sir for sharing this information.
It was joy reading this article. The concept of ATIL has nicely and timely been addressed. I don’t see anybody giving this much of detail. You have gone to the root of the problem.
Superbly compiled document…. full of insight.
🙏
Is it not possible that terraces used for farming are very porous in nature, therefore, naturally the rain water would all be retained in the terraces and would easily penetrate down, making it heavier and a slip surface would become venerable to trigger a landslide.
Am I correct?
Right you are sir. The terraces do retain water and the people of the region understand that this could initiate slope instability – bunds are therefore not provided in far flung hard to manage terraces and these often kept outward sloping.
But then, out here the point of discussion is to highlight the fact that damaged terraces promote high density flow during intense rainfall resulting in gully erosion and landslides. These initiate from the terraces and so ATIL.
Facts very well written. Many times we just study a landslide from its toe (river bank/road cutting) to its head/crown but if we take pain and traverse in upslope and take geological and other information many a times we came to know that there’s another factor as you have rightly described as ATIL which works silently and we just see toe erosion by river or anthropogenic activities (road cutting etc) or heavy rainfall as being the main triggering factor for overburden mass movement along rock- overburden contact plane.
Once when I went for some landslide investigations along Pinder valley, say for famous Narainbagarh slide I went beyond the crown of slide and after discussions with locals took traverses in up hill and found these agriculture terraces to be irrigated regularly and found another (hidden) reason/factor for its recurrence.
Thanks for sharing valuable information on the subject 🙏🙏
This is an excellent Report. A suitable action is required after getting all these data.