Garhwal Post Bureau
Dehradun, 22 Aug: Doon Library and Research Centre (DLRC) and SPECS jointly organised a lecture on “Dharali Flash Flood – Just Another Disaster in the Timeline!” at the Doon Library and Research Centre Auditorium, here, today.
The lecture was delivered under ‘The Dehradoon Dialogue (TDD) Series’, as a maiden effort, with organisational support from Doon Library and Research Centre (DLRC) and SPECS. The Dehradoon Dialogue has been formed with an objective of sharing and discussing various science, society, policy and development issue pertaining to the current overall development framework of the state. The output of such dialogues will be extensively shared with the concerned sectoral development planners to augment and support the rightful planning and execution of such activities.
The day’s session started by a welcome address by Chandrashekhar Tiwari of Doon Library and Research Centre (DLRC), wherein he also thanked Dr Dinesh Sati for providing timely technical analysis and presentation on the recent Dharali Flash Flood.
Hari Raj Singh, on behalf of TDD, introduced Dr Sati, who brings with him 43 years of rich experience in Field Geology. He has worked with prestigious institutions such as WIHG, Sagar University, KDMIPE-ONGC, and CRRI-New Delhi. His expertise spans structure and tectonics, landslides, hydrogeology, and engineering geology. Dr Sati has conducted extensive on-groundwork across the Himalayan ranges, including Nepal and Bhutan.
Even today, his sharp insight in on-site planning and troubleshooting remains unparalleled.
Dr Dinesh Sati said, “While we mourn the innocent lives lost and the colossal property damage in the Dharali flash flood, it must be acknowledged that the hazard was not unprecedented. Almost every year during monsoons, such disasters inundate habitations and infrastructure across the Himalayan extent.”
The instability of landforms in such drainage basins can be mapped and quantified through satellite imagery. With different precipitation datasets, hazard modelling can be conducted, and based on such outputs, infrastructure development projects in vulnerable regions can be planned with greater safety assurance.
Dr Dinesh Sati shared the timeline of various small geological and climatic events in the Dharali area over the years as follows:
Inundation history of Dharali
An August 2018 Flash flood triggered by cloud burst, buried two dozen homes /hotels and destroyed two hectares of orchards and farmland.
A 20 July 2015 surge pushed lots of rubble and debris into homes and damaged infrastructures.
A June 2013 flood caused significant damage to the market area, 5-10 feet of sediment entered the homes and hotels located alongside the drain.
On 3 August 2012, a cloudburst in upper catchments caused flash flood and debris to flow through village lanes and market area, damaging homes and shops.
In August 2010, heavy rain led the stream breach that flooded school ground and houses, leaving the village waterlogged for several weeks.
In August 1978, the entire valley was heavily damaged due to extensive rainfall leading to Kanodia gad incident near Dabrani; at that time possibly a major wedge cum planar failure would have temporarily blocked the Kheer Ganga and its breaching resulted in a flash flood.
In 1835, presumably Kheer Ganga witnessed a major flash flood that formed an alluvial fan at its mouth near Dharali by pushing the river course of Bhagirathi away towards Mukhba. This alluvial fan later housed farmlands and orchards.
Understanding and analysing the flash flood in the Kheer Ganga Basin
To identify the root cause of the flash flood in Kheer Ganga basin, one first needs to know the site and try to understand the interplay of agencies in the offered physiographic and geologic conditions, especially the materials that are precariously or unstably resting in that basin and prone to move. Preliminary estimates of all these can be made using satellite data.
- Elevation range – 2511m – 6062m from MSL
- Total length of the basin ≈ 10Km and maximum width ≈ 3Km
- Catchment area – 17.70 sq km (17,724,434 sq.m.)
- Area under glaciers – ≈6,000,000 sq.m.
- Total area – glacier = 11,724,434 sq.m.
- Excluding area under rocky faces and forest make approximately half of the basin. This part should have weathered mass+ colluvium +ancient moraine = 5,862,217 sq.m.
- Riverbed material -7000×15 = 105,000 sq.m.
A shallow glacial lake – at EL. 5200m has an area – 0.8156m over the basin boundary
Dr Sati further shared an analysis leading to the current situation as follows:
The susceptibility of the debris fan to flooding was not a new phenomenon, yet the villagers and hoteliers were allowed to construct their buildings. The infrastructures like highway, bridges, telephone/ internet, electricity and drinking water supply lines greatly helped in managing the disaster but if the same have been compromised, relief and rehabilitation works would naturally become difficult.
Uttarakhand for the first time instituted a separate ministry to manage and look into the disasters, because being located in the Himalaya, the State is prone to many such natural disasters. The USDMA, with which the erstwhile DMMC was merged, should have been in the forefront of locating probable zones of hazards in coordination with Uttarakhand Space Application Centre (USAC), and issue early warnings about them but these departments are themselves visible only after some hazard struck. “I have no idea if these departments are working on those lines or was there any forewarning of Dharali disaster, but if not earlier, they should proactively work for preventive measures rather than sticking to relief and rehabilitation or preparing autopsy reports on the disasters,” stated Dr Sati.
Way forward to have a safer Uttarakhand:
- While the state mourns the death of innocent lives and the colossal loss of properties in the Dharali flash flood, the hazard was not unprecedented.
- Marginalisation of human habitation due to disasters is bound to increase basically due to population explosion against limited natural resources; as a result even the most vulnerable areas are being occupied by the communities. Over time unpredictable global climate changes have also increased the risks.
- Landslides and flash floods are inundating habitations and infrastructures here and there across the Himalayas almost every year during wet periods.
- Except for the areas covered under the ice sheets, the instability of landforms in drainage basins can be mapped and approximately quantified using satellite data.
- The time has come that people should be ready with different plans for the vulnerable areas, duly tested with variability of risk factors. e.g., with different precipitation data, modelling of hazard potential can be done, and based on those outputs, infrastructure development projects in the vicinity can be planned, which would assure safety.
Dr YP Singh and Dr Brij Mohan Sharma felicitated Dr Dinesh Sati for his enlightening talk and especially the technological way forward for planning and execution of various development projects in the state of Uttarakhand.
The lecture was attended by students of Sunrise Academy, Uttaranchal University, DBS College, researchers of Wadia Institute of Himalayan Geology of Dehradun, and Sanyukt Nagrik Sangathan, Civil Defence. A total of 123 participants attended this insightful presentation.
Those who attended the Dialogue and the deliberations thereafter included Balendu Joshi, Vibha Puri Das, RK Mukerji, Jairaj, Sushil Tyagi, Ranu Bisht, Rajeev Oberoi, Dr DP Dobhal, Dr Deepak Bhatt, Kusum Rawat, Jairaj, Atul Sharma, Devender Budakoti, Col Amit Agarwal, Dr Anil Jaggi, Bhumesh Bharti, Neeraj Uniyal, Chandra Swami and many other members of civil society.
