Non-monsoonal landslide in Rudraprayag, Uttarakhand

Most landslides occur during the monsoon season, but the one around Sari in Rudraprayag district of Uttrakhand occurred during the winter season on February 28, 2022. Despite there being no causalities, occurrence of landslide during the winter season is certainly unusual. After winter season flood in Dhauliganga in February 2021 and post-monsoon rainfall induced landslides in Nainital in October 2021, this incidence highlights the surprises and challenges in store for disaster managers, and they are accordingly required to gear up their preparedness.

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अब ऐसा भी नहीं है कि आज से पहले मानसून अवधि से इतर भू-स्खलन हुवे ही न हो – सितम्बर 23, 2003 को वरुणावृत व मार्च 30, 2005 को रमोलसारी में क्रमशः मानसून के बाद व पहले भू-स्खलन हुवे है। पर ज्यादातर भू-स्खलन मानसून में भारी बारिश के दिनों में ही होते है और ऐसा होने का वैज्ञानिक औचित्य भी है।

एक ओर जहाँ मानसून अवधि से इतर हुवे भू-स्खलन विशेष रूप से भू-वैज्ञानिको के लिये कारणों की विवेचना को कठिन बना देते है, वही दूसरी ओर यह आपदा प्रबन्धको के लिये भी अनेको चुनौतियाँ प्रस्तुत करते है।

फिर पिछले साल धौलीगंगा में जाड़ों में आयी बाढ़ के बाद मानसून उपरान्त विशेष रूप से नैनीताल के मुक्तेश्वर क्षेत्र में मानसून उपरान्त हुयी बेमौसमी बारिश के कारण हुवे भू-स्खलनों के बाद इस साल फिर से जाड़ों में हुवा रुद्रप्रयाग का यह भू-स्खलन कहीं प्रकृति की चेतावनी तो नहीं ?              

External trigger a must

Not that landslides do not occur during dry season; Varunavat landslide in Uttarkashi district initiated on Sepetember 23, 2003 and Ramolsari landslide in Tehri Garhwal initiated on March 30, 2005 – post and pre monsoon season respectively. The Law of Inertia or Newton’s First Law of Motion however makes putting forth a logical explanation of these landslides difficult.

The Law of Inertia does not allow even the most unstable rock mass present on upper reaches of the hill to move downslope on its own, and asserts that it should remain indefinitely at that very place until an external force is applied to set it into motion. An external trigger is therefore invariably required for initiating a landslide and in case of landslides accompanying an earthquake this trigger is provided by ground shaking.

Ground shaking is however not as common as landsliding and most slope instability related incidences take place during the rainy season wherein presence of water changes the dynamics of forces acting on the debris and rock mass resting on the hill slope; increased weight and enhanced pore water pressure together with reduced frictional forces tilt the balance in favour of forces acting in the downslope direction. Presence of water thus provides the trigger for landslides to initiate.

Landslide of February, 2022

Like Varunavat and Ramolsari landslides a massive mass movement took place in Jhali Math village of Sari Gram Panchayat of Rudraprayag exactly one year and 03 weeks after devastating Dhauliganga flood in the morning hours (around 0800 hrs) of February 28, 2022.

Though there was no loss of human lives or cattle, a  number of cowsheds were destroyed by the mass movement, and safety of a number of residential houses in the affected area was compromised. 11 families were accordingly  evacuated from the affected area and shifted to relief camps set up in the proximity.

The incidence site is located NNW of Gauchar in Chamoli district on the right bank of Alaknanda river. No geological investigations have so far been undertaken in the area and therefore no one really has any clue regarding the trigger that initiated this slide. The affected area however falls in the proximity of Alaknanda Fault and thus the rock mass is expected to be sheared and weak.

Varunavat and Ramolsari landslides indicate that slowly and continuously operating physio-chemical and mechanical weathering processes have the potential of initiating landslides at locations that satisfy other geological conditions for downslope mass movement even in the absence of rainfall. Moreover, geotectonic evolutionary history of the terrain makes the rocks of the terrain highly fractured and jointed and many a slopes in the region show high landslide hazard potential.

The challenges

Except for earthquake most other disasters including landslide that are prevalent in the region are generally perceived to accompany monsoonal rains and, therefore, it is no surprise that monsoon period is considered as being disaster season for which the state routinely undertakes special preparations – from prepositioning equipment, machinery and manpower for prompt and effective response to stock piling of essential items and food grain to tackle exigencies arising out of areas being cut off due to disaster incidences.

Non-monsoon period is considered to be relatively safe from disasters  and disaster managers generally tend to utilise this period for undertaking various  other disaster management-related activities – updation of databases, plans and SOPs to risk assessment, mitigation, capacity building and awareness.

During the previous year Dhauliganga valley of Chamoli district was devastated by floods during the winter season that is lean flow season for glacier fed Himalayan river. Then there were heavy rains in post-monsoon period in October and ensuing landslides caused widespread losses, particularly in Nainital district. Yet again there has been a major landslide incidence in Rudraprayag district during the winter season.

These incidences warrant that the disaster managers get rid of conventional disaster-season mentality and devise ways of ensuring prompt and effective response all through the year.

This would no doubt require additional resources – particularly manpower, as the personnel spared during the monsoon period by various line departments are not likely to be available all through the year.

Moreover, all the manpower cannot also be dedicated for response as various important pre-disaster activities have also to be carried out for ensuring disaster resilience.

Capacity building of the local volunteers could be a great help in this regard. In the rugged and inaccessible mountainous terrain of the region, induction of formal responders is often constrained by weather conditions and restricted access and response is carried out by the locals alone. If trained in search and rescue and first aid local volunteers could promptly and efficiently discharge preliminary response functions and save precious human lives.

Creating stores of search, rescue and lifesaving equipment together with relief supplies at strategic locations across the state would further strengthen local level response capabilities.

More than anything else this would greatly help on the aftermath of a big earthquake that is the major concern for the region.

Planned and phased escalation of the capabilities of State Disaster Management Authority is therefore a must to effectively addressing the challenges put forth by Mother Nature.