MANY GLOFS ARE WAITING TO BURST
This is the state of Himalayas. A fresh red alert of snowfall, a fresh new brewing danger of avalanche…a fresh spell of dry weather another danger of glaciers breaking up to create another avalanche and flood, a fresh spell of warm weather a new danger of flash floods. Come what may, there is one or another danger that is lurking. Waiting to explode the Himalayas and its environs are always in constant danger, in constant threat, in a constant disaster mode…
At one time it was Sikkim, another Himachal still another Uttarakhand. Arunachal will join soon. Just sometime back, the Lhonak Lake burst, unleashing a flood of water that eventually raised the water levels of the Teesta River to alarming levels and its associated destruction downstream as it led to a series of cascading effects including the washing away of Chungthang dam even before the gates could be opened.
Occurrences of glacial lake outburst floods (GLOFs) have become increasingly frequent.
Most of these lakes are located in remote and unpopulated mountain valleys. A GLOF event can cause fatalities and damage assets far downstream, sometimes spanning tens of kilometres.
What happened in Sikkim was that GLOF covered everything, and the accumulated silt cannot be excavated due to the possibility of army explosives buried in the sand and the flood has destabilized the river’s slopes through toe erosion, which will cause long-term concerns..
It was GLOF that caused the Kedarnath floods. The burst of Chorabari Lake or Gandhi Sarovar caused the Kedarnath floods in 2013. The lake is bounded on one side by hard rock and on the other by a lateral moraine. The lake was fed by snow rather than the waters of the Chorabari glacier, which has receded over time. Because there was no natural drainage, the lake was packed to the max and burst its moraine barrier.
There was no mechanism to have known such a risky devastation that was brewing.
A heavy rain accelerated the snow melt into the lake causing this extreme event. Had there been a mechanism to forecast these rains, the picture would have been different.
Of course, the disaster was aided by other causes too like deforestation, large scale conversion of Pine to Oak Plantation, large-scale dam building, the illegal sand mining that removed the protective cover at the base of the slope increased its vulnerability to various types of mass movements, landslides, and slippages.
WARNINGS IGNORED
Both of these disasters Uttarakhand and Sikkim were, by and large, preventable, and varied ameliorative measures could have been taken as preventive steps.
None of the early warning sensors installed for the critical glacial lakes in Sikkim in 2013, 2016 and even a month before and it survived long enough to forewarn residents downstream.
GLOF was a significant risk to Teesta III. In 2005, the carrying capacity study of the Teesta basin – based on which the environment ministry cleared Teesta III – had noted that the region was “quite susceptible to disastrous hazards due to Glacial Lake Outburst Floods”.
A study by the National Remote Sensing Centre and the Indian Space Research Organisation (ISRO) in 2012-2013 highlighted the associated risks of the lake, estimating a high outburst probability of 42 per cent.
In 2016, an expedition led by Sonam Wangchuk of the Students’ Educational and Cultural Movement of Ladakh warned about the potential of a GLOF event.
A LURKING DANGER
If the lessons are not learned, there will be another GLOF waiting to happen in the Geepang Gath lake in Himachal Pradesh. The lake is at high risk of breaking its banks and causing a flash flood because of its increasing size, local topography and melting permafrost, a situation similar to the glacial lake outburst flood downstream of the Lhonak Lake in Sikkim. Geepang Gath has grown over the years to become the largest lake in the state.
Geepang is in a situation very similar to Lhonak’s. It is a high risk. Himachal Pradesh and Uttarakhand in the western Himalayas and Sikkim in the eastern Himalayas have glacial lakes at high risk of GLOFs given temperature increase change, so careful monitoring and timely mitigation efforts are needed.
The lake may grow more than double its size, and warming permafrost in the surrounding steep slopes makes it susceptible to failure.
The highest risk is to infrastructure downstream, which includes the Sissu helipad, with severe implications for evacuations and other emergency response action.
PREVENTION OF ANY DAMAGE IN FUTURE
If the water level in Gepang Gath can be brought down artificially, it would significantly reduce the risk of an outburst flood.
There are many ways to reduce volumes in glacial lakes, which include controlled breaching, construction of an outlet control structure, pumping or siphoning out the water, and making a tunnel through the moraine barrier or under an ice dam, lowering the lake level by 10 and 30 m to evaluate the changes in the GLOF intensities downstream of the lake.
CAN GLACIAL HAZARDS SUCH AS GLOF BE FORECASTED?
It is not possible to completely prevent GLOF and other glacial hazards. Nevertheless, their potential to cause destruction can certainly be minimized. There are examples. Of late, scientists have been working on a project to reduce the water level of the lake to prevent potential GLOFs.
MONITORING
The first step in tackling the threat from these glacial lakes is to start monitoring the glaciers more actively and regularly. Of course, there is no need to watch every glacier. Glaciers in one basin do not have remarkably different properties from another bay. Thus, if one or two benchmark glaciers in each basin, preferably those that are more easily accessible, are chosen, and extensive investigations are conducted, the results can be extrapolated to the remainder of the glaciers in the basin or state.
It is essential to get people and measuring instruments on the ground to monitor the situation. That is why accessibility becomes a vital factor. Monitoring glaciers means measuring the bathymetric changes, the mechanisms of expansion of the glaciers, changes in water levels, discharge balance, mass balance, and other attributes. It requires a lot of workforce and money.
There are few parameters for forecasting if taken care of can prevent such events.
- Surveillance through Satellite forecasting humidity sensors, wind sensors and snow depth sensors can be done by setting sensitivity zones. However, relying only on satellites and remote sensing will not be enough.
- Synthetic aperture radar imagery can automatically detect changes in water bodies, including new lake formations.
- A dataset that tracks the progressive changes is crucial for any decision-making.
There are other indices as well, such as: –
- Changes in the water level of the lakes
- Monitoring discharge of rivers, controlled discharge and breaching, pumping and siphoning out water and making a tunnel through the morainic barrier or under an ice dam
- Structural geotechnical measures include the construction of channels for gradual and regular discharge.
Constructing channels for gradual and regulated water discharge from these lakes can help to reduce the pressure on them and minimize the chances of a breach. Additionally, it also reduces the volume of water that flows into the flash flood. Alarm systems can also be established at the lakes to alert the community downstream whenever an overflow is likely.
OTHER SUGGESTIONS
High-resolution remote-sensing satellite systems, drones, ground-based monitoring stations, and ground observations are necessary to acquire an accurate and comprehensive perspective on Himalayan snow coverage, glaciers, and glacial lakes. INSAT-3DS will add significantly now.
The setting of a comprehensive alarm system. Besides classical alarming infrastructure consisting of acoustic alarms by sirens, modern communication technology using cells and smartphones can complement or even replace traditional dire infrastructure. A preparatory response drill will also have to be worked out, like what India has done for cyclones and tsunamis. Moreover, glaciology needs to be taken instead as a part of policy intervention. The behaviour of fish needs to be studied in detail as their movement and concentration can give a natural indication of such an event.
Disclaimer : The above is a sponsored article and the views expressed are those of the sponsor/author and do not represent the stand and views of The Tribune editorial in any manner.
