Our casual attitude towards safety measures can be easily noticed in our routine dealings, and disaster safety is really no exception.
Despite easy access to state of art surveying and communication tools concerned authorities have not cared to monitor either treated slopes of Varunavat Parvat in Uttarkashi or destabilised slopes of Balia Nala in Nainital. Both these are located in the district headquarter and have potential of posing grave threat to significant population of these tourist destinations of Uttarakhand.
In this context it is interesting to note that the British Raj authorities were not satisfied merely with treatment works carried out meticulously in accordance with the recommendations of the Ramsay Committee that was constituted after September 18, 1880 Sher-ka-Danda landslide, and to ensure safety of life and property in the lake city they resorted to regular monitoring of the slopes around the Naini lake in order to be doubly sure of the efficacy of the treatment works, and to assess landslide threat in future. Before being discontinued unceremoniously this practice of slope monitoring continued till 1997.
Successful monitoring of the hill slope around Naini lake highlights the importance of vision, resolve and will power over technology and resources.
वर्ष 1980 में नैनीताल के भीषण भू-स्खलन से प्रभावित होने के उपरान्त सीमित संसाधनों के बावज़ूद अंग्रजो के द्वारा न केवल इस भू-स्खलन के कारणों का गहन अध्ययन किया गया, बल्कि विशेषज्ञों की संस्तुतियों के अनुरूप इसका उपचार भी किया गया।
उपचार के उपरान्त भी वो लोग सुरक्षा के प्रति लापरवाह नहीं हुवे और किये गए सुरक्षा कार्यो की प्रभाविकता के प्रति आश्वस्त होने के साथ ही भविष्य में सम्भावित भू-स्खलन के खतरे के आंकलन के उद्देश्य से उनके द्वारा विशेष रूप से भू-वैज्ञानिकों द्वारा दिए गये सुझावों के अनुसार नैनी झील के चारो ओर की पहाड़ियों की निरन्तरता में निगरानी की गयी।
आप विश्वास करे या न करे, पर नैनीताल में पहाड़ी ढालो की निगरानी का यह कार्य आज़ादी के बाद वर्ष 1997 तक जारी रहा।
आज से 100 से भी अधिक वर्षो पूर्व की गयी संवेदनशील ढालो की निरन्तर निगरानी से सबक़ लेते हुवे आज के आपदा प्रबन्धको को संवेदनशील व भू-स्खलनग्रस्त ढालो के साथ ही भू-स्खलन के उपरान्त उपचार किये गये स्थानों की निगरानी के साथ ही उपचार कार्यो के नियमित रख – रखाव के लिये बजट की व्यवस्था करनी चाहिये और साथ ही निरन्तरता में की जा रही निगरानी से प्राप्त आंकड़ों का उपयोग प्रभावी भू-स्खलन चेतावनी के लिये करना चाहिये।
The ground fissures
A number of prominent ground fissures were observed on the hill slopes around the Naini lake after Sher-ka-Danda landslide of September 18, 1880; one extended from Mayo Hotel to St. Loo Cottage through the Government House, other one further east split into a rock on the summit of the little ridge above Fairlight, while the third proceeded from the Club to the end of the Cheena ridge through the road west of Fairlight.
Differential movement across these ground fissures as reflected in the form of cracks in neighbouring structures was a cause of grave concern for the British Raj. A Committee was therefore constituted on April 22, 1895 to consider the safety of the old Government House.
The recommendations
After careful examination of the area the Committee deemed it necessary to carry out regular monitoring of the hill slope and recommended:
(i) Establishing two observation points for assessing ground movement of the Government House hill, of which one be on the Cheena slope
(ii) Observation points on the Cheena slope be selected at convenient points such as Fairlight Hall (Tonnochy), Jemsond Villa and the Upper Mall.
(iii) For the purpose of continuous observation, a point be selected on the Government House hill together with one or more points on the adjacent hills in the same vertical line.
(iv) The Committee suggested the Club, west of Edgehill, and main building of Oak Openings as being appropriate points as these were all in the same vertical plane as the theodolite station at Jesmond Villa.
(v) At least two such theodolite observation stations be immediately established and exact position of the instrument be fixed by a mark cut on a block of Nalena stone built into a masonry base.
(vi) Masonry pillars be constructed on selected points on each side of the crack along the Government House ridge for observing any movement which might take place along the crack during and after the rains.
Monitoring of Kailakhan hill
On August 10, 1898 cut away cliff overhanging the Balia suspension bridge below the Brewery gave way destroying the bridge. Two small slips, on the face of the hill occurred on August 15, 1898 and a line of springs showed up prominently across the middle of the hill face, and water gushed out from these as if the whole hill side was filled with water.
These were all precursors of a major landslide that occurred in the afternoon of August 17, 1898 and brought down a large slice of the Kailakhan hill into the Balia ravine above the Brewery. The debris of this landslide blocked Balia Nala together with Durgapur and Motapani streams forming three lakes that drained out in a day.
The landslide obliterated part of the bridle road to Nainital between Durgapur and the Brewery, buried a shop and the toll house near the Brewery, and overwhelmed certain buildings of the Brewery. 28 persons were killed in this incidence.
The area of the slipped portion, triangular in shape, and the debris below was estimated to be 0.29 sq km, and the landslide was described as being a larger edition of Sher-ka-Danda landslide of 1880.
Charles Stewart Middlemiss described this as being another instance of superficial layer of the disintegrated surface rock getting detached from the more solid material below, and flowing down the hill side in a semi fluid condition.
After detailed geological investigation of the area Middlemiss recommended that the hillside be watched with theodolite in the same manner as the Sher–ka–Danda. This led to the monitoring of the Kailakhan hill from Bleak House observatory.
The Committee of 1907
The Committee of 1907 recommended adoption of special measures for better observation of the settlement on the eastern bank of Edgehill ravine. For this the Committee suggested:
(i) Supplementing the existing pillars so as to form three lines crossing the Edgehill depression and extending well beyond its influence on either side.
(ii) Carefully observing and recording the level of these pillars every year after the rains, with reference to a fixed benchmark on the north side of the hill at St. Loe gorge.
(iii) The observations be taken by the District Engineer himself, and the results be embodied in his annual report.
(iv) All the tell tales put up for crack measurements on various walls be invariably dated.
Precautionary evacuation
Proper observation of Charta Hill started in 1912 when six pillars were erected with horizontal and vertical readings of these taken.
In 1915 the maximum total subsidence of this hill was observed to be more than 5.5 m and the stability of the hill was assessed as being so doubtful that by the orders of the Chief Engineer potentially dangerous areas at the toe of the hill were demarcated, and the inhabitants thereof were evacuated during the rainy season.
Four additional pillars on the centre line of the probable slip were thereafter erected, and a special observation hut was constructed and provided telephone connectivity.
Charta hill landslip of 1924
04 persons were killed in this landslide that took place around the Brewery.
After this landslide cracks were observed in the lower Charta Hill as well.
11 new pillars were therefore erected in 1926 and reference mark was changed, as the house to which the original reference mark was affixed had been damaged by the landslide. The new reference mark was painted on a block of rock on Beluakhan hill.
The Committee of 1927
After detailed study of the hill slopes around the Naini lake and analysis of the records of the theodolite stations, the Committee appointed on September 6, 1927 recommended erection of 15 additional pillars; 4 on Manora spur, 3 on Kalmukhet spur, 2 on Old Reserve Police Lines spur, 2 on Charta Hill observatory spur, and 1 each on Bellavue spur, Gangipur spur, Galloway House spur and Glenlee spur. Apart from these one mark was also made on the central gable of Endcliffe.
Coulson Committee – 1937
Based on slope monitoring data of previous years Coulson Committee constituted in 1937 concluded that the old main fissure of Sher–ka–Danda was healing gradually due to the mitigation measures adopted in the past – all mainly directed at preventing seepage of excess water along the main fissure and the cleavage and stratification planes of the shales and slates constituting the hill.
The Committee however admitted that the movement has not seized totally.
Report of the Committee at the same time expressed concern over worsening state of affairs in Sher–ka–Danda hill to the southeast of St. Loo Gorge, and documented appearance of fresh ground fissures in that area.
The Committee at the same time warned of a major landslip if adequate measures were not taken to rectify the existing state of drainage. The Committee also stressed upon need of afforesting the denuded areas of the Sher–ka–Danda hill.
Monitoring discontinued
The story of discontinuing the monitoring of hill slopes around the Naini lake is equally interesting – vegetation growth around the theodolite observation stations obstructed smooth monitoring, and therefore Forest Department was requested for permitting lopping of trees.
Not appreciating the importance of monitoring the hill slope, and having gained environmental consciousness the Forest Department however did not respond, and the practice was discontinued in 1997 without any formal order for doing so.
Present scenario
Despite real time and detailed monitoring of hill slopes having become simple and cost effective due to technological advancements in surveying and communication no hill slope in the country, including Nainital, is being monitored comprehensively on real time basis for risk assessment and warning generation.
It is important to note that the treated slopes are presently being taken for granted, and there exists no strategy for post treatment monitoring and follow up maintenance. This is evident from the neglect of the slopes of the Varunavat Parvat that were treated after the landslide of September 23, 2003. Despite district headquarter of Uttarkashi being located at the base of the Varunavat Parvat monitoring and maintenance of the treated slopes is not being resorted to. To add to it no agency has been formally entrusted the responsibility of maintaining the treatment works and there exist no budgetary allocation for doing so. The treated slopes have thus started to show signs of distress.
Despite geologists and geotechnical engineers acknowledging the importance of monitoring the destabilised slopes for preparing a comprehensive restoration and treatment strategy, no destabilised slope including Balia Nala in Nainital is being monitored on real time basis.
Apart from a few stray experiments, there at present exists no operational landslide early warning system in the country.
Key lessons
After the devastating Sher-ka-Danda landslide of September 18, 1880 the British Raj authorities treated the destabilised slopes meticulously in accordance with the recommendations of the Ramsay Committee. They were however not satisfied with that alone, and did not ignore possibility of future threat.
The British Raj authorities therefore invested on regular monitoring of the slopes around the Naini lake in order to detect slightest signs of instability or distress and undertake appropriate measures to ward off threat to human lives and property.
The British Raj authorities at the same time resorted to regular geological investigations of the vulnerable slopes. They at the same time created a system with adequate budgetary allocation to ensure routine maintenance of structures created for stabilising the hill slope.
Monitoring of the hill slopes around Nainital has an important lesson for all disaster managers – Mitigation or treatment measures, howsoever robust do not rule out possibility of hazard occurrence in future, and thus there exists no scope for disaster managers to completely ignore the treated slopes.
Masses are sure to forget the previous incidences and become careless with passage of time – may be because of the fading affect bias. It is however the duty of the disaster managers to not let their guards down and continue with measures for early detection of hazard and timely implement measures for ruling out possibility of any disaster.
Way forward
Regular monitoring of identified vulnerable slopes is the first step in realistic assessment of the risk posed by these, and accordingly preparing a suitable risk reduction strategy.
Taking clue from the British Raj authorities the disaster managers need to undertake systematic monitoring of all destabilised slopes where these have potential of threatening human interests, and put in place a reliable and robust warning system for ensuring timely evacuation of the population likely to be affected in case the monitored slope exhibits signs of distress.
Apart from vulnerable slopes, monitoring is a must for treated slopes that generally infuse an illusion of safety amongst the masses. It needs to be clearly understood that without monitoring one can only guess about the efficacy of the treatment measures.
All treated landslides, particularly in the proximity of habitations should therefore be regularly monitored and the responsibility of their routine maintenance should be entrusted to an identified agency with appropriate budgetary allocation. Monitoring and maintenance of Varunavat Parvat in Uttarkashi could be an ideal starting point for this. Moreover, this is particularly pertinent as a number of vulnerable slopes along the National Highways are presently being treated by National Highways Authority of India (NHAI).
Monitoring of the destabilised slopes could provide exact details of the degradation processes operating in the area. This data could be highly useful for preparing detailed plan for holistic restoration of the landslide affected areas.
For effective restoration of the destabilised slopes it is required that active slides in the proximity of major habitations be monitored and this can be initiated with the monitoring of the landslide along Balia Nala in Nainital.
Even though most regional landslide warning systems are based on finely calibrated rainfall threshold real time monitoring is a must for site specific warnings. Two pronged strategy is therefore suggested – (i) rainfall threshold based regional landslide warning system be setup on the basis of closely spaced network of meteorological observation stations with real time data transmission capability, and (ii) real time monitoring of the critical sites be resorted to for site specific landslide warning.
Lastly local community should invariably be involved in monitoring, warning generation and dissemination as also maintenance of the treated slopes, and reporting signs of distress on the slopes around their habitations.
आपके द्वारा इस लेख का सार हिन्दी में भी दिया गया है जिसका आभार. भविष्य में भी इसी प्रकार हिन्दी में जानकारियां दिया करे.
लेख से कई बाते पता लगी – उस समाय के लोग शायद सुरक्षा को ले कर हमसे कहीं ज्यादा संवेदनशील थे और उनके प्रयासों में पारदर्शिता व ईमानदारी थी जो आज के समय में कही दिखाई नहीं देती.
बहुत काम की जानकारियां देने के लिए आभार।