An Advanced Warning System (AWS) installed almost a month before the disaster at Lhonak Lake in north Sikkim, failed to send any alert before the lake burst triggering a flash flood in river Teesta, official said.
“Two AWS were installed at Lhonak Lake and Shako Cho Lake between September 9 and September 19 this year. Unfortunately, the system didn’t send any early warning. Most probably it wasn’t working when the incident took place,” said VB Pathak, chief secretary of Sikkim.
On the night of October 3, the Lhonak lake burst triggered a flash flood that killed at least 92 people.
It is one of the largest and fastest growing proglacial lakes in Sikkim and is among the 11 large glacial lakes monitored by the Central Water Commission.
Officials said that an early warning about a possible Glacial Lake Outburst Flood (GLOF) could have given authorities more time to evacuate people living in houses along the river.
Two expedition teams including Swiss scientists and comprising 14 persons each, were sent to the lakes in September to install the AWS.
It was a joint operation, which was conceived by the National Disaster Management Authority (NDMA) in collaboration with Sikkim state disaster management authority and Swiss Agency for Development and Cooperation.
“It was a pilot-project, which was supposed to generate data on the lakes based on which an Early Warning System (EWS) was to be developed. The data was to be monitored by the Swiss agency. Even though the one installed in Shako Cho was sending data, the one in Lhonak didn’t generate any data,” said another senior official.
With the Swiss-system failing to generate any kind of alert before the flood, the Sikkim government has now sought the help of ISRO.
“I have written to the chairman of ISRO and director of North Eastern Space Application Centre in Shillong to keep a watch on Lhonak, Shako Chu and other glacial lakes in Sikkim. I have requested them to analyze satellite images and data and let us know if any immediate steps need to be taken. We are receiving regular updates from them,” said Mathur.
Even though the machines failed to generate an early alert, a robust response and evacuation model developed by the Sikkim government for such events, including GLOF, dam burst and cloud burst, helped in the evacuation process.
“Around 2am on Wednesday, I heard frantic whistles and people shouting. Then somebody banged on my door. As soon as I got out from the bed, there was ankle-deep water in my room. My roommate and myself rushed out to reach higher ground. Within minutes, the floodwaters covered everything,” said Sidhant Chetri, a resident of Rangpo in east Sikkim.
Several tourists who were stranded in Lachen and Lachung towns of north Sikkim recalled how they were alerted by the hotel staff of an impending flood. They could also hear the constant sound of whistles that were sent out as warnings.
“The hotel employee who alerted us told us to grab only important documents, cash and medicines before evacuating. By the time we reached out scores of people including tourists and locals were scrambling uphill. We could hear the river down below fuming,” said Malay Kumar Saha, a tourist who was stranded in Lachen before the army rescued him.
Senior officials of the Sikkim’s land revenue and disaster management department said that residents living in Chunthang and other north Sikkim towns and villages, that are vulnerable to flooding events, were made to undergo mock-drills at least once a year based on special response and evacuation models. They were also shown computer simulations of such extreme events and when to respond.
“Special response and evacuation models have been developed for such vulnerable towns and the people were made aware of the plan through computer simulations, mock drills and regular campaigns. When an alert came, they knew what to do and where exactly to go,” said Anil Raj Rai, relief commissioner of Sikkim.
The first alert reached the director of the state’s disaster management authority at around 10:42pm on Tuesday night that water level was rising in river Teesta. The alert had come from ITBP personnel posted close to Lake Lhonak.
The alert was soon passed on to the 24X7 control room at the secretariat which is always manned by three officials. Warnings were issued to the districts after which police personnel on duty began whistling to wake up people. Hooters were sounded and by 5am, the control centre was bustling.
“It could have been worse. The flood hit around 80 towns and villages. It struck at the dead of the night when everyone was fast asleep. The casualty and missing figures could have been much higher had it not been for the evacuation,” said a senior official.
Source: Hindustan Times