In the present glacier burst in Uttarakhand, I think the reduced downstream flow warning was not heeded. The labourers working in tunnels should not have been allowed in as a flash flood was to be expected with the impending glacier burst.
Ganga glacier burst, some overlooked facts.
Glacier bursts don't happen as suddenly as cloudbursts do. They give sufficient time for timely action to avoid or at least minimise the consequent losses.
Glaciers continue to melt to feed the perennial rivers. At times, small parts of glaciers break and flow down with river stream. They further break and also melt as they reach lower areas with warm temperatures. The problem arises when a glacier part big enough to block the river flow completely or substantially breaks from the main glacier. With the river blockade, a lake starts forming in the upstream area of the point of the blockade. Simultaneously, the water flow downstream is reduced considerably and this is the sure sign that some glacier had blocked the flow in the upstream region. This is usually noticed by villagers living along the banks of the river. They on their own or on the persuasion of authorities move to higher locations.
They know that the glacier caused blockade would break anytime under pressure from impounded water and cause huge damages. The longer the blockade stays, bigger would be the chances of it causing damages. We at Radio Kashmir Jammu used to broadcast repeated warnings in news bulletins and otherwise advising people to move to higher locations whenever glaciers blocked the Chenab river beyond Kishtwar town. It continued sometimes for days. Authorities watched the situation through helicopters over the glacier blocked location. I remember, at one time there was a proposal to blast the glacier using artillery guns.
In the present glacier burst in Uttarakhand, I think the reduced downstream flow warning was not heeded. The labourers working in tunnels should not have been allowed in as a flash flood was to be expected with the impending glacier burst. The huge torrent that washed away two of under construction hydel projects, must have been caused by massive water column created behind the blockade not in a day but over days.
This was the time to evacuate people and machinery from areas downstream. This was also the time when sluice gates of Srinagar dam and other dams downstream should have been opened to drain out water so that huge water column due to flash flood could be accommodated to moderate its impact.
While blaming massive damage to the construction of hydroelectric dams in the fragile Himalayas, a point must be noticed that it was ultimately the Srinagar Dam that absorbed the impact of flash floods saving any loss to Haridwar and other towns downstream.
Ajeet Singh, From Hisar.