Flood in Assam could be minimised with the help and application of early warning system, says Chandan Kumar Duarah, a science journalist and conservation activist in Assam. Satellite data has been playing a crucial role which was ignored during Assam flood. Several countries including China, Russia and France collaborated with India on sharing satellite images of the scale of inundation. As signatories to the The International Charter Space and Major Disasters, any of the 32 member countries can send a ‘request’ to activate the Charter. This would immediately trigger a request by the coordinators to space agencies of other countries whose satellites have the best eyes on the site of the disaster.
Based on an activation request by the Indian Space Research Organisation (ISRO) on July 17, France’s National Centre for Space Studies, China National Space Administration and ROSCOSMOS of Russia shared satellite images of the flood situation in the districts of Dhubri, Marigaon, Barpeta, Dhemaji, Lakhimpur in Assam with ISRO’s National Remote Sensing Centre. ISRO’s CARTOSAT satellites too got the Indian space agency its own images.
Ravish Kumar, spokesperson of the Ministry of External Affairs, said in response to a query from The Hindu that combining earth observation assets from different space agencies allows resources and expertise to be coordinated for rapid response. This was a “standard practice” and in the past ISRO too had provided information to other space agencies in response to similar requests. In August 2014, for instance, ISRO’s CARTOSAT shared images after an activation request from China after an earthquake struck Yunan province and killed 398.
Since 2000, when the Charter came into operation there have been about 600 activations and data from 61 satellites have helped with disaster operations in 125 countries.
The Brahmaputra River has the second highest sediment yield per square kilometre in the world, exceeded only by that of the Yellow River in China. India’s central government and the state government of Assam have planned to dredge the Brahmaputra, with an initial amount of Rs 4 billion ($57 million).
One purpose of this dredging is to reduce flooding by allowing more water to stay in the river. The second is make the Brahmaputra navigable for large vessels – the river has been designated National Waterway 2 by the Inland Waterways Authority of India. It is planned as a vital component of trans-boundary inland waterways transport between India and Bangladesh.
Before the dredging starts, it is important to understand the nature of sediment transport in the Brahmaputra, because the dredged-out river is likely to be filled up again, partly or completely.
Sediment load of the Brahmaputra
The sediment deposited in the Brahmaputra varies across its length. At Tsela Dzong in Tibet it is about 150 tonnes per square km. But as the river crosses the Himalayas and reaches Pasighat at the foothills of Arunachal Pradesh in India, the deposit increases tenfold to 1,495 tonnes per square km. This shows that the river gathers sediments from soft rocks and landslide-affected areas of the Himalayas. The Higher Himalaya Range contributes about 70% of the sediments of the Brahmaputra, as explained by S. Krishnaswami and K. Singh in the September 10, 2005 issue of the journal Current Science.
The Brahmaputra then flows through Assam – forming the Assam valley, with the high Himalayas in the north and the Meghalaya plateau in the south – before entering Bangladesh. As measured at a station in Majuli – the largest river island in Assam – the suspended sediment load is slightly higher at 1,513 tons per square km, higher than at Pasighat, due to the contributions from the rivers Dibang and Lohit, which also flow down from the Himalayas on the north bank of the Brahmaputra.
Since the Brahmaputra is a trans-boundary river, data on its water discharge and sediment load are classified and thus the public has no access. Researchers can get the data after a lengthy process and only if they pledge not to share the data in public.
Sediment loads are measured as both suspended load and bed load. Suspended load is the sediment being carried by the water at the time of measurement, while bed load is the sediment that has settled down on the riverbed. Old data – published despite the ban – reveal that on an average the Brahmaputra transported 402 million tonnes of suspended sediment annually between 1955 and 1979 at the Pandu measuring station in Guwahati, the largest city of Assam.
According to Water and Power Consultancy Services, the average annual sediment yield between 1978 and 1991 was 527 million tonnes at Pancharatna near Goalpara, just a little upstream of the place where the river enters Bangladesh from India.
But this average means little. During the monsoon from May to October, the Brahmaputra transports 95% of the annual suspended load at Pandu at an average daily rate of 2.12 million metric tonnes. It would need over 141,300 trucks – of 15 tonnes each – to carry this away.
Although suspended sediment is measured at a few stations on the Brahmaputra, no convincing attempt has been made to measure its bed load. Dulal Goswami wrote in the 1989 (15.1) edition of the Indian Journal of Earth Sciences that he had estimated the bed load using several empirical equations and concluded that the bed load at Pandu was of the order of 5-15% of the total sediment load of the river.
Dredging feasible? Desirable?
Since suspended sediments form the majority of the load, will it be possible to maintain the dredged channel suitable for large vessels at the desired width and depth during the monsoon, when there is daily input of 2.12 million metric tonnes of sediments into the river?
And to what extent is this desirable? The authorities have stated that the main purpose of dredging the Brahmaputra is to prevent high flows from inundating its banks, which result in floods. But the valley of Assam has been created from the sediments deposited by floods of the Brahmaputra and its tributaries. During last two million years it has deposited 200-1,000 metre thick sediments by flooding and lateral channel migration.
Natural floods have several benefits besides increasing soil fertility. But artificial heavy floods have been created in Assam either due to breaching of embankments or sudden release of impounded water to keep dams safe. Such floods deposit enormous quantities of sterile sands rather than fertile sediments. For flood control, the solution should lie with improving or disbanding embankments and dams rather than with dredging.
Dredging seems to be a superficial answer to the challenge of drainage congestion and managing floods. Proper planning and a detailed study of the basic aspects of this government project are needed. A critical analysis of the data on both sediment input and dredging depth, together with a far better idea of the bed load, is necessary before starting this mega project.
Jogendra Nath Sarma is a retired professor of applied geology at Dibrugarh University, Assam, and the author of two books on the Brahmaputra.
Neepco authorities at Yajuli in Lower Subansiri district of Arunachal Pradesh were compelled to open three gates of the Ranganadi dam on Thursday due to the river overflowing.
Heavy rains in Assam and Arunachal Pradesh have led to the Ranganadi dam being opened, which resulted in 76 villages in Assam being submerged and the lives of thousands being affected.
Neepco authorities at Yajuli in Lower Subansiri district of Arunachal Pradesh were compelled to open three gates of the Ranganadi dam on Thursday due to the river overflowing.
The release of dam water has submerged 76 villages in Lakhimpur district, impacting nearly 25,000 people. The swirling waters have damaged 3,560 hectares of standing crop.
The Lakhimpur district administration had on Thursday evening alerted people to be cautious but not panic over the release of excess water from Ranganadi reservoir.
On March 11 last year, release of dam water had resulted in the Ranganadi wreaking havoc in 220 villages, breaching embankments at Amtola and near Lakhimpur.
Over one lakh people have been affected by the heavy rains and flash floods in Assam and Arunachal Pradesh. Ferry services in Assam, where six districts experienced flash floods, have been stopped due to the rising river waters.
Assam’s Dhemaji district, known for its perennial floods, is teetering on the brink with 173 villages inundated, affecting 47,471 people. Nearly 7,108 hectares of standing crop have been damaged. The district administration has opened three relief camps where 805 inmates have taken shelter.
A portion of bridge number 693 over Jiadhal river between Dhemaji and Bordoloni stations has been washed away.
The Northeast Frontier Railways said eight trains have been short terminated or cancelled.
In Arunachal Pradesh’s capital Itanagar, incessant rain since Thursday has caused heavy flash floods resulting in a child’s death and three people missing. Three more people have died in the state due to floods and landslides.
Early on Friday, a massive landslide triggered by rains has blocked roads in the state’s Papum Pare district. Reportedly a Tata Sumo with 10 passengers was buried under the landslide. However, all 10 have been rescued. Landslides triggered by rains has become a common situation. Many spots at the Yupia-Potin Trans-Arunachal Highway have been blocked due to the landslides. (NDTV)
Chief Minister Pema Khandu condoled the deaths and directed the district administration and the disaster management department to continuously monitor the situation
Landslides and flood struck two areas of Arunachal Pradesh capital Itanagar on Friday, claiming two lives, including that of a minor. Three others were reported missing.
According to official sources, the catastrophe was triggered by incessant rains for the past two days. Two persons were rescued by a search and rescue team. The incident occurred at Modirijo and Donyi-polo areas in the morning.
Twelve houses were fully washed away while eight others were damaged partially in Modirijo in the incident. Similarly, five houses were fully damaged and four others were partially damaged in Donyi Polo area by the flood and landslides. Some cars and bikes were also swept away to a flooded river.
Water supply lines to capital region have also been badly affected. There were also incidents of landslides between Potin and Pangin portion of National Highway 13 near Aalo-Bam-Pusi-Doke-Tirbin, Hoj-Potin and some other parts of the state.
Chief Minister Pema Khandu condoled the deaths. He directed the district administration and the disaster management department to continuously monitor the situation. He also passed instructions for evacuation of people from vulnerable areas. He announced immediate release of ex-gratia payment of Rs.4 lakh each to the next of kin of the deceased.
Khandu issued directives to authorities to maintain vigil during the monsoon season to avoid human casualties and damages. He also gave strict instructions to ensure preparedness to tackle the catastrophe.
National Disaster Response Force personnel patrolling in the Periyar after the water level rose in the river. | Photo Credit: H_Vibhu
The Indian Space Research Organisation’s satellites and Doppler radars played a key role in weather monitoring and forecast, and provided critical inputs for various agencies involved in the rescue of stranded citizens during the floods in Kerala last month.
Pointing out that most of the districts in Kerala — mainly Iddukki, Patthanmthitta, Ernakulam, Thrissur and Palakkad — had received more than expected rainfall with a deviation of more than 164% in August, the space agency said it had monitored the whole event through its various satellites, helping the prediction and safety measures.
In just the first 20 days of the month, Kerala had received the highest rainfall for the entire month in 87 years, with Idukki district breaking a 111-year record for the highest rainfall for the month, as per the India Meteorological Department’s records. This rainfall had triggered floods in several parts of the State and caused widespread havoc, according to the agency.
ISRO not only extended support through its space-based sensors, but ground-based sensors as well. Two of its radars — one C-Band Polarimetric Doppler Weather Radar (DWR) at TERLS, Vikram Sarabhai Space Centre (VSSC), Thiruvanthapuram and one S-Band DWR at Kochi — were continuously monitoring the weather on 24X7 basis up to 500 km radius.
The data was transferred to IMD, Meteorological and Oceanographic Data Archival Centre (MOSDAC), and Space Application Centre (SAC) for further data analysis and centralised weather monitoring. The information was made available in near real time for the public through the MOSDAC and IMD websites.
According to a press release by the ISRO, the radars had helped in long range weather surveillance, forecast and nowcast of the weather and rainfall activity in Kerala. The National Disaster Management Authority and Kerala State Disaster Management authority were continuously monitoring the data received by the radar and images were continuously updated on the IMD website for making decisions on various activities.
The DWR system provides quantitative information in digital form — the intensity and mean velocity of cyclones along with rainfall rate and accumulation. It improves the understanding and forecasting of thunderstorm, hailstorms, tidal wave height, wind turbulence and shear as well as the probable intensity of rain in and around the region, the press note said.
The data, it said, had helped civic bodies in evacuation and rescue of stranded citizens during the floods. (Source: The Hindu)
China has alerted India about the rising water in river Tsangpo, called Siang in Arunachal Pradesh and Brahmaputra in Assam, leading to possibility of floods in downstream areas, Arunachal Pradesh MP Ninong Ering said today.
“The local authorities told me that the Chinese government has conveyed to Indian government that there is a possibility of floods in parts of Arunachal Pradesh. We have taken the alert seriously and cautioned people,” he told PTI.
Ering said the communication from China came following heavy rains in that country which has swollen Tsangpo.
“The local authorities told me that the Chinese government has conveyed to Indian government that there is a possibility of floods in parts of Arun ..
After massive floods ravaged Kerala, the situation seems grim in North East India as over 12 have died so far in Nagaland due to landslides and flash floods. Assam and Arunachal Pradesh remain on high alert due to heavy rainfall in upper riparian China.
The Central Water Commission (CWC) has, however, said that the situation should not create panic as an increase in China’s Tsangpo river should not inflict very severe damages on the Indian side, even as it asked the states to remain vigilant.
Incessant rain in Nagaland since July have caused floods and landslides in several areas claiming at least 12 lives and rendering thousands homeless. The Chief Minister of Nagaland, Neiphiu Rio, tweeted seeking help — with a video showing the damage that is caused in Nagaland due to this rain.
Major roads, including NH-29 was severely damaged, while landslides isolated several villages from the mainland. At least 4,000 families have been evacuated so far by the state disaster response authorities, with the state government seeking more help from Centre to carry out relief operations. The worst-affected areas included state capital Kohima, Tuensang, Wokha, and Dimapur.
Representational image. PTI
According to official records of the Assam State Disaster Management Authority, at least 50 people have died in flood and landslide in Assam this year. According to All India Radio, at least 15,000 people have been affected by flash floods in Assam’s Golaghat and Dhemaji districts.
More than 600 hectares of crop area was severely damaged and over 1,488 people continue to stay in relief camps as low-lying areas remain inundated. Three rivers in the state — the Dhansiri, Brahmaputra and Jia Bharali — are flowing above the danger mark. If Brahmaputra swells any further following the rainfall in China, it could be especially devastating for the state.
Assam is highly flood-prone even in normal monsoon conditions. The state’s river waters collect a tremendous amount of silt and other debris and raise the level of the river beds. Therefore, it becomes impossible for the main channel to cope with the vast volume of water received during the rains. Reports from Dibrugarh said the district’s deputy commissioner Loya Maduri has directed the stakeholders to remain alert about the possible rising of water level of the Brahmaputra. Similar measures have also been taken in Dhemaji district, official sources said.
In Arunachal Pradesh, people living in low-lying areas like Jarku, Paglek, SS Mission, Jarkong, Banskota, Berung, Sigar, Borghuli, Kongkul, Namsing and Mer, along the Siang river have been asked to remain alert as China reported that Tsangpo river, called Siang in Arunachal Pradesh, was in spate. The unusually high waves in the Siang river have created fear among the people of the two Arunachal Pradesh districts and the administration has cautioned the people to refrain from venturing into it for fishing, swimming and other activities, an official said. Large-scale erosion was seen on the left bank of the river towards Lower Mebo of Mebo sub-division in East Siang district in the past few days and 15 houses were washed away in Seram-Ramku village, the official said.
Mebo MLA Lombo Tayeng, who is also an advisor to Chief Minister Pema Khandu, said that river water at present is “totally muddy which indicates that there might be some activities in the Chinese side”. The MLA also urged upon the Centre to take up the matter with Beijing and sought flood control measures. A red alert has been hoisted for residents of Borguli, Seram, Namsing, Mer and Sigar villages on the left bank of Siang as water volume in the river is rising, he said adding it was due to large-scale siltation on the river bed.
The Chinese authorities alerted India about the unprecedented situation where Tsangpo broke a 150-year record with swollen waters and informed the Centre about a possible flood-like situation in downstream states of Arunachal Pradesh and Assam. According to a Chinese government report, 9020 cumecs of water was discharged into Tsangpo as observed at various stations until Wednesday. The Tsangpo river originates from China’s Tibet and flows into Arunachal Pradesh, where it is called Siang, and then Assam, where it becomes the Brahmaputra, and later drains into the Bay of Bengal through Bangladesh.
This was the first time this year that China shared the river data with India, the official said. China began sharing data from 15 May, while it started sharing data for the Sutlej river from 1 June. The sharing of data came after the two sides held talks over the issue in March this year. The data is shared twice daily until October this year.
China provides data from three hydrological stations — Nugesha, Yangcun and Nuxia, lying on the mainstream of the Brahmaputra, also known as Yarlung Zangbu by Beijing — and from the hydrological station at Tsada for the Sutlej river, known as Langqen Zangbo.
The affidavit said that the Kerala government, till the release of water from the 13 shutters, was managing the spate.
The Kerala government on Thursday claimed in the Supreme Court that sudden releases of water from the Mullaperiyar dam was a cause for the floods in the State.
In an affidavit, Kerala slammed Tamil Nadu for allegedly ignoring its repeated entreaties for controlled release of water from the reservoir to facilitate the evacuation of thousands living downstream.
Kerala said communications from its Water Resources Secretary and the Chairman of the Supervisory Committee on Mullaperiyar dam to gradually release water “at least” at 139 feet evoked no “positive assurances” from the Tamil Nadu government.ALSO READKeep level under 140 foot, says Mullaperiyar panel
“The request was made to facilitate the district administration and State Disaster Management Authority to get sufficient time to evacuate people so that they would not be hit by the flash floods in their sleep in the stealth of the night,” Kerala Chief Secretary Tom Jose informed the Supreme Court.
Instead, water from the Mullaperiyar reservoir was “suddenly discharged by opening all the 13 shutters to Idukki downstream at 2.40 a.m. on August 15. Around 9,000 cusecs of water was let out between 8 a.m. to 1 p.m. and 21,450 cusecs at 2 p.m. on August 15.”
“The sudden releases from the Mullaperiyar dam forced us (Kerala) to release more water from the Idukki reservoir,” Kerala submitted.
The affidavit said that the Kerala government, till the release of water from the 13 shutters, was managing the spate by controlling spill and letting a major portion of the flood waters to escape to the sea by implementing a strict operational control over the spill of the two largest reservoir systems of Idukki and Idamalayar in synchronisation with eight small other reservoir systems in the Periyar basin.
Kerala urged the Supreme Court for the need for sufficient flexibility of operation of the Mullaperiyar gates during moderate to high floods. It is imperative that Mullaperiyar reservoir should have enough manoeuvrability to avert loss of human lives in floods and other crisis in the future, Kerala submitted. It said the current gate operational protocol was deficient and its requests since 2014 for an overhaul has not produced a response.
It said gradual releases should start when the water level reaches 136 feet itself, so that there should be at least 1.548 TMC space, which translates into 17,917 cusecs for 24 hours. “Thus we would get at least 24 hours response time to evacuate people and can avoid flash flooding of the downstream area,” the affidavit said.
The Supreme Court has fixed the permissible water level of Mullaperiyar dam as 142 feet.
Kerala said a Supervisory Committee, headed by the Chairman, Central Water Commission (CWC) and secretaries of both States as members, should be formed with authority to take decisions by a majority opinion regarding operations during floods or similar calamities.
Further a Management Committee, reporting directly to the Supervisory Committee, should be formed to manage the day-to-day operations of the Mullaperiyar Dam. This Committee should be headed by a Chief Engineer/Superintending Engineer of the CWC with both Chief Engineers/Superintending Engineers of the two States, Mr. Jose proposed.
The affidavit was filed in response to a petition filed by Idukki-resident Russel Joy highlighting the perils of a dangerously-high water level in the British-era dam, made worse by the utter lack of co-ordination between the two State governments and a non-existent disaster management plan. Mr. Joy submitted that this was the biggest flood to hit the southern State since the Great Flood of 1924. He said people residing downstream to Mullaperiyar dam live with a constant sense of fear.
A three-judge Bench led by Chief Justice of India Dipak Misra is scheduled to hear the case on August 24. By