CMD, APS group
The sudden flood on 07 Feb 2021 (Sunday morning) in the Dhauli Ganga, Rishi Ganga and Alaknanda rivers triggered widespread panic and large-scale devastation in the high mountain areas. At least 76 persons have been killed and over 150 are still missing after a portion of the Nanda Devi glacier broke off in Uttarakhand’s Chamoli district, triggering an avalanche and a deluge in the Alaknanda river system. The sudden flood in the middle of the day in the Dhauli Ganga, Rishi Ganga and Alaknanda rivers – all intricately linked tributaries of the Ganga – triggered widespread panic and large-scale devastation in the high mountain areas. Two power projects – NTPC’s Tapovan Vishnugad Hydel Project and the Rishi Ganga Hydel Project – were extensively damaged with scores of laborers trapped in tunnels as the waters came rushing in. The glacial outburst has raised many eyebrows and fingers about early warning, preparedness and rescue operations and overall handling of such disasters. This sent alarm bells ringing which set in motion my inclination to study the NDMA Guidelines on the subject.
Mountain regions are characterized by sensitive ecosystems, enhanced occurrences of extreme weather events and natural hazards. They also symbolize the conflicting interests between economic development and environmental conservation. With rapid global warming, fragile-mountain cryosphere and landscapes are evolving and new threats of landslides, glacial lake outburst floods (GLOFs), avalanches, cloud burst, drought and flash floods are posing grave risks to the vulnerable mountain communities. The Indian Himalayan region (IHR) is facing critical challenges while coping with the adverse effects of climate change. The disappearance of mountain glaciers, expansion of large glacial lakes and the formation of new glacial lakes are amongst the most recognizable impacts of global warming in this environment. IHR lies in Seismic Zones IV and V making the region highly prone to earthquakes. Flash floods and GLOFs have killed thousands in many parts of the world. Some of the largest events have occurred in the Indian Himalayas such as the Kedarnath disaster in Uttarakhand (2013) and Parechu river flash floods in Himachal Pradesh (2005). Despite these losses, disaster risk management related to GLOFs has not been mainstreamed into development policies and programs.
Objectives of the NDMA Guidelines
The National Disaster Management Agency (NDMA) has partnered with the Swiss Agency for Development and Cooperation (SDC) along with national experts from concerned Indian institutions for the development of the National Guidelines on Management of Glacial Lake Outburst Floods (GLOFs). The main objective of the NDMA Guidelines is to generate awareness of various aspects of dam failure hazards in India and to implement suitable actions to reduce both the risk and costs associated with these hazards. The Guidelines envision to improve administrative response, bringing together the relevant scientific capabilities of the nation to eliminate the losses from glacial and landslide hazards. The primary aim of these guidelines is to develop a strategy that encourages the use of scientific information, maps, methodology, guidance for early warning system, response management, development and implementation of initiatives to reduce losses from glacial hazards. These Guidelines also describe the awareness, preparedness, capacity development, research and development, regulations and enforcements and roles and responsibilities of the local, state and national ministries/ departments along with the various scientific organizations and institutions to reduce the potential risks. These guidelines aim to enable concerned ministries or departments of state/ UT, central governments and other stakeholders to take concerted action for preparedness, prevention, mitigation, and response to GLOFs. These guidelines also emphasize awareness and capacity building of the relevant stakeholders. The possibility of GLOF and LLOF in the Indian Himalayan region (IHR) are escalating very rapidly and pose a threat to the lives of millions of people living in this region. NDMA Guidelines lays down the roadmap to mitigate the impacts of glacial hazards and risks, to develop disaster resilient communities and significantly reduce the loss of lives and assets. These guidelines meant to assist the central ministries, departments and states to formulate their respective DM plans and extend necessary cooperation/ assistance to NDMA for carrying out its mandate.
What is GLOFs
The melting of the glaciers leads to the accumulation of water in the glacial lakes behind the natural dams made of pebbles, sands, ice and ice residue. These dams are called glacial or moraine dams. When such dammed water suddenly gets released, it results in floods known as GLOFs. The moraine dam is a weak structure and this can give way to an abrupt failure of the dam atop the glacial lake. The glacial lake holds a large amount of water, and a dam failure can possibly release millions of cubic meters of water in a very short time, leading to a disastrous flooding downstream. Among other such events that have been recorded, peak flows have gone up to a whopping 15,000 cubic meter per second. Due to the climate change, glaciers in the Himalayas are retreating, leading to an increase in glacial lakes. This has become a potential risk for the infrastructure and life downstream. An inventory of water bodies and glacial lakes was carried out by the National Remote Sensing Centre in the Himalayan region of Indian river basins between 2011 and 2015. This study found that as many as 352 water bodies and glacial lakes were present in the Indus basin, while this figure was 283 for the Ganga river basin and 1,393 for the Brahmaputra.
What Factors contribute to Glacial Hazards (GLOF & LLOF)
Factors contributing to the hazards/ risks of moraine-dammed glacial lakes include: (a) large lake volume; (b) narrow and high moraine dam; (c) stagnant glacier ice within the dam; and (d) limited freeboard between the lake level and the crest of the moraine ridge. Potential outburst flood triggers include avalanche displacement waves from (i) calving glaciers, (ii) hanging glaciers, (iii) rock falls, (iv) settlement and/ or piping within the dam, (v) melting icecore; and (vi) catastrophic glacial drainage into the lake from sub-glacial or en-glacial channels or supra-glacial lakes.
Monitoring Glacial Lakes
Between early warning (hours to minutes), and longterm monitoring of dangerous lakes (annual to biannual), there is a challenge to detect new threats that may emerge over the course of days, weeks, and months. This can include rapidly expanding glacial lakes in response to prolonged heavy rainfall, new glacial lakes as a result of blockages in the glacial hydrological system or associated with surging glaciers, and newly formed landslide lakes. As many of these processes are more likely to occur during the monsoon months, cloud cover can prevent the use of optical remote sensing. There are therefore opportunities to exploit Synthetic-Aperture Radar (SAR) imagery to automatically detect changes in water bodies including new lake formations during the monsoon months. Methods and protocols could be developed to allow year-round remote monitoring of lake bodies from space, as a compliment and precursor to ground-based early warning systems at critical lakes are unpredictable. Thus, more time is available to plan and implement measures to reduce the likelihood of GLOF. This can be ensured through continuous monitoring. The various means and methods which can be adopted for monitoring are done under arrangements of National Remote Sensing Centre (NRSC) sponsored by Climate Change Directorate, Central Water Commission (CWC), New Delhi, Govt. of India using IRS-AWiFS sensor data of 56m spatial resolution. The continuation of glacial lake monitoring is being carried out by CWC (every year) on monthly basis during monsoon months using IRS-AWiFS satellite data. The entire GIS database on glacial lakes and water bodies over Himalayas mentioned above is available with CWC. In addition to or instead of remote sensing approaches, a combination of precipitation thresholds and river stage monitoring can be considered for the monitoring of landslide dammed lakes, as described:- Object-Based Image Analysis (OBIA) technique, field investigation of critical lakes, monitoring by trekking guides, precipitation threshold for landslides, measurement of river and lake water level.
Early Warning Systems
EWS is generally planned on short term, medium term and long term. Short term systems include automated alert service, toll free number, smart phone based app, creation of common signage for GLOFs and LLOFs, use of local mass media and use of posters, wall paintings and hoardings. Medium term systems include awareness through documentaries, creation of village task force and creation of citizen science approach, and long term awareness program on GLOFs & LLOFs, use of traditional art form, awareness through participation approach, involvement of not for profit organization, awareness among local youth and national data center on GLOFs/ LLOFs.
Present Mechanism for Early Warning System
The early warning system (EWS) is an integral component of risk management for natural disaster. It has been listed as one of the five priorities under Hyogo Framework for Action (HFA) for building disaster resilient nations and communities, and is one of the seven global targets of its succeeding document, the Sendai Framework for Disaster Risk Reduction (SFDRR), 2007 with clear messages, dissemination systems that reach those at risk, and practiced and knowledgeable responses by risk managers and the public. A detailed discussion on early warning systems is covered in section 4.6 of these guidelines. The traditional framework of early warning systems is composed of three phases: (i) monitoring of precursors, (ii) forecasting of a probable event and (iii) the notification of a warning or an alert before an event take place. Thereafter, the emergency response system becomes active. The purpose is to recognize the fact that there needs to be a response to the warning, where the initial responsibility relies on emergency response agencies. International standards were set by the United Nations office for Disaster Risk Reduction (UNDRR).
Risk reduction: What needs to be done
According to the guidelines issued by NDMA, the first step is to identify and map such lakes, and then take measures to make structural improvements (artificial drainage system i.e., siphoning techniques, control blasting etc.) that would prevent these dams from sudden breaches. Moreover, for events where such a breach occurs, a mechanism would need to be put in place to save lives as well as property. Field observations, the lakes’ and dams’ geomorphologic and geotechnical characteristics, and records of past events can help in identifying lakes that are potentially dangerous. Meanwhile, the NDMA has also suggested that changes in water bodies like formation of new lakes can be automatically detected with the help of Synthetic-Aperture Radar (SAR) imagery. Experts say a warning system for flash floods in states like Uttarakhand is far less complicated, and in most instances, an impending disaster can be detected several hours, even days in advance. A lake burst, for example, does not happen all of a sudden. There are ample indications that can be monitored. Changes in water level, discharge in the rivers, excessive rainfall in the catchment areas etc., are all things that can be measured. Regular monitoring can sometimes tell us weeks in advance about the danger, and in many cases, it could even be possible to avert the tragedy. For instance, a lake burst can be prevented in some cases if a drainage is constructed that lets out water at regulated levels.
There are some works that have been carried out to identify such lakes. However, other aspects like establishment of a robust early warning system, as well as the framework for development of infrastructure and construction and excavation in vulnerable areas are still a work in progress. In the guidelines, the NDMA mentions that India does not have uniform codes for construction, excavation or grading, as against other countries. It has added that an effective way to reduce risk from GLOF, a no-cost method is to restrict construction and development in vulnerable areas. Moreover, habitation in prone areas should also be prohibited.
On the other hand, even globally the number of implemented and operation early warning systems for GLOFs is very small, and in the Himalayan region, there are only three reported instances of the implementation of monitoring and sensor-based technical systems for GLOF early warning, and of these, one is in China and two are in Nepal. Meanwhile, India has a great history of successful warnings regarding Landslide Lake Outburst Floods (LLOFs), and this dates back to the 19th century.
Disaster preparedness refers to measures taken to reduce and mitigate the effects of a disaster, and forms a core component of the proactive stage of disaster risk management. Preparedness can considerably relieve the severity of impact during the scenario of a disaster. Given the rarity of GLOF and LLOF events in the IHR, not much is known to the community. While structural support (embankments, artificial drainages etc.) may be feasible to some extent, however, it cannot be widely replicated because of inadequate technology, financial and logistic constraints (in-accessibility to mountain reaches). Non-structural/ institutional support is therefore, one of the key mechanisms to be strengthened in such contexts. For this Central and State Governments, in collaboration with various stakeholders and NGOs, need to work closely to implement measures of preparedness on the ground.
I ndia has already seen the benefits of an effective early warning system for other natural disasters, most noticeably for cyclones. Every year, potentially thousands of lives are being saved because of accurate cyclone prediction, the availability of shelters, and timely evacuation of people from danger zones. India also has a working early warning system for tsunami, which offers barely half an hour of lead time. Though there has been no opportunity, thankfully, to test this in a real-life situation, mock drills and simulations have shown that it would be possible to shift the vulnerable populations even in this small time period. In recent years, early warning systems have been developed for heat waves and flooding as well, and these too have helped in saving human lives.
The survey and monitoring of glaciers are done by the Geological Survey of India (GSI), which is under the Ministry of Mines; Scientific research is coordinated by the Department of Science and Technology; Climate change studies and impacts are the domain of the Environment Ministry; while rainfall and precipitation are monitored by the India Meteorological Department (IMD), which functions under the Earth Sciences Ministry. The Central Water Commission works on the hydrology aspects; avalanches are monitored by an agency that is part of Defense Research and Development Organization (DRDO); while remote sensing is being done by the National Remote Sensing Agency (NRSA), which is a part of ISRO. In addition, State Electricity Boards and Irrigation Departments are also stakeholders in the glaciers. They are all doing legitimate and important works. They are there because glaciers overlap with their mandate. But it is not the main job of any of these. There has to be one agency that coordinates all the activities and is focused only on glaciers. The creation of National Centre for Glaciology could possibly be the answer for single nodal agency to coordinate the cumulative effort to reduce such disaster in IHR.