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Explained | Assam’s annual tryst with devastating floods

Aerial view of the flood-affected area as seen by Assam Chief Minister Himanta Biswa Sarma during his survey, in Silchar on June 23.

Aerial view of the flood-affected area as seen by Assam Chief Minister Himanta Biswa Sarma during his survey, in Silchar on June 23. | Photo Credit: PTI

The story so far: The Brahmaputra Valley that encompasses the Northeast part of India witnesses floods almost every year, leaving behind a tale of death and destruction. Even before the onset of monsoon in Assam this year, incessant rain over the past week has wreaked havoc, with much of Assam submerged, crops destroyed and lakhs displaced.

By June 25, the death toll rose to 118 and the town of Silchar in Cachar district remained submerged for the sixth straight day, according to officials. The total population affected by the floods, however, declined to 33.03 lakh in 28 districts as against the previous day’s figure of 45.34 lakh in 30 districts, a bulletin issued by the Assam State Management Disaster Authority (ASDMA) said.

Nearly 2.7 lakh people, meanwhile, have been evacuated and moved to relief camps. This is the second time in less than a month that Assam has been ravaged by floods. At least 30 people were killed in the State due to floods in May. 

The extent of destruction

So far, Assam has recorded an excess rainfall of 109 per cent in June. As per the meteorological department, the State has witnessed 528.5 millimetres of actual rainfall against the normal 252.8 millimetres. More than 5,000 villages and croplands have been inundated, with the Brahmaputra river breaching its embankments due to incessant rainfall. The river is presently flowing above the danger level at Dhubri, Goalpara, Guwahati, Tezpur,and Neamatighat.

Besides the Brahmaputra, rivers Beki, Manas, Pagladiya, Puthimari, Kopili, Subansiri are flowing above the danger level and Kopili is above the ‘highest flood level’ in Kampur area of central Assam’s Nagaon district. Urban areas of Barpeta, Cachar, Darrang, Goalpara, Kamrup (Metro), Karimganj, Nalbari and Udalguri are also under water.

Heavy rain has triggered landslides in Cachar, Dima-Hasao, Goalpara, Hailakandi, Kamrup (Metro) and Karimganj districts, throwing normal life out of gear. Road and rail services remain disrupted in several parts of the State. Food and potable water is not easily available. Roads and bridges have suffered serious damage. 

The destruction is not limited to humans alone. Some 60,000 animals have been washed away and around 36 lakh were affected in the current wave of floods, according to the ASDMA report. More than 15 per cent of the Kaziranga National Park has been inundated with the Brahmaputra flowing above the danger level, an official statement noted. At least five animals, including a leopard, have been killed in floods in the national park so far this year.

A man moves his cattle to a safer place through a flooded field after heavy rains in Nagaon district, Assam, June 21.

A man moves his cattle to a safer place through a flooded field after heavy rains in Nagaon district, Assam, June 21. | Photo Credit: Reuters

Considering the critical state of the situation, the Army has been deployed with the National Disaster Response Force (NDRF) in Hojai, Nalbari, Barpeta, Cachar, Darrang and Kamrup districts. Over 2 lakh people have been sheltered in 800 relief camps, while 825 relief distribution centres have been set up.

Prime Minister Narendra Modi has, meanwhile, assured the Assam Government of all help from the Centre. Assam CM Himanta Biswa Sarma on June 18 visited relief camps in Kamrup and Darrang districts to take stock of the situation.

Why does Assam get flooded every year?

Floods have been a way of life for people living in Assam. For centuries, the southwest monsoon has been followed by floods in low-lying areas of Assam, which is why it is referred to as ‘floodplains’. People once waited for floods as the mineral-rich water would replenish the fertility of their land. The Brahmaputra is also critical to the Kaziranga National Park as it is bound by the river on one side. In recent years, however, the extent of devastation due to floods has increased significantly. 

Around 40 per cent of Assam’s land — 31.05 lakh hectares of the total 78.5 lakh hectares — is prone to floods, according to the National Commission on Floods. Roughly, this is around 10 per cent of the total flood-prone area of the country. Nearly 30 per cent of Assam’s land — 22.54 lakh hectares — was affected by floods from 1998 to 2015, according to a report by the Indian Space Research Organisation (ISRO). It adds that about 2.2 million hectares suffered damage due to floods at least once during this period. Over the years, more areas have come under the grip of floods. The annual area affected by floods in Assam averages around 9.3 lakh hectares, according to the Water Resources Ministry of the State Government. The State suffers an annual loss to the tune of Rs 200 crore on an average due to floods. 

A soldier rescues a child from a village in Guwahati, Assam, June 20.

A soldier rescues a child from a village in Guwahati, Assam, June 20. | Photo Credit: AP Photo

According to Central Water Commission data from 1953 to 2016, 26 lakh people are affected every year in Assam on an average, while 47 persons and 10,961 animals die and the State incurs damage of up to Rs 128 crore. For a population of over 3 crore, this leaves a huge impact on the economy of Assam. 

The Brahmaputra factor

Assam, situated at the foothills of the Himalayas, comprises two valleys — Brahmaputra and Barak, named after the respective rivers — and two hill districts, along with a huge network of over 20 large rivers and 50 tributaries. The mighty Brahmaputra river originates from the Himalayas and enters India through Arunachal Pradesh before flowing into the Bay of Bengal. It flows through Assam over a length of around 650 km with an average width of 5.46 km, making it the principal river that crisscrosses the floodplains. 

The Brahmaputra river basin

The Brahmaputra river basin | Photo Credit: Brahmaputra Board

Coming from the Kailash range at an elevation of over 5,000 m, the river gets highly sedimented by the time it enters Assam and the average slope of about 2.82 m/km comes down to about 0.1m/km. Due to this flattening of the slope, there is a sudden drop in velocity and the river deposits huge quantities of sediment and other debris collected from hilly terrains on the riverbed, raising its level. During summers, the sedimentation increases as soil erodes with the melting of glaciers. Multiple research papers have noted the high level of sedimentation of the Bramhaputra, which may raise the level of the river and reduce its water carrying capacity.

Additionally, the monsoon is intense in the Northeast.According to the State Disaster Management Authority, annual rainfall averages around 2900 mm with maximum precipitation in June and July. The Water Resources Ministry of Assam states that 85 per cent of the annual rainfall in the Brahmaputra basin takes place during the monsoon months. “Besides the valley gets a good amount of rainfall in April and May due to thunderstorm activities which account for flood during heavy rain in June, when the soil is already saturated,” it adds.

During monsoon, highly sedimented river water from the Himalayas combines with rain-fed water bodies in India, resulting in water spilling over land in the narrow valleys, leading to floods.

Flood hazard map of Assam. Different colours represent different hazard classes.

Flood hazard map of Assam. Different colours represent different hazard classes. | Photo Credit: Source: ISRO, 2018

Another notable factor is that Assam lies in a seismically active zone. An increase in construction activities in the recent area has resulted in frequent landslides. Earthquakes and landslides also push sediments and debris into rivers, which further raises the riverbed and increases the risk of floods.  

Riverbank erosion

As sedimented rivers move through the state along with their tributaries, they take with them soil and sediment from banks. Soil erodes and rivers expand as it gets more area and this results in flooding. This erosion of the land alongside rivers has emerged as a serious problem for Assam — a major cause of the internal displacement of people due to the disappearance of villages. The width of Brahmaputra has increased up to 15km due to bank erosion at some places in Assam.

Surveys carried out at different periods reflect an alarming picture regarding widening of the Brahmaputra.

Surveys carried out at different periods reflect an alarming picture regarding widening of the Brahmaputra. | Photo Credit: Assam Government

A report on climate change by the Assam Government states that more than 4.27 lakh hectares of land has been eroded by the Brahmaputra and its tributaries since 1950 — nearly 7.5 per cent of the total State area. Nearly 8,000 hectares of land is lost every year on average. 

Assam is also losing its farmland due to riverbank erosion. More than 3,800 square kilometres of farmland in Assam — around half the size of Sikkim — has been lost since 1954.

Human intervention

Embankments are constructed to confine the course of a river. This solution, however, has evolved to be an added challenge over time in Assam. Construction of embankments first started in Assam in the 1960s to control floods. Six decades later, most of these embankments have either outlived their utility or are in bad condition. Many others were washed away. Every year, as floods follow monsoon, river water breaches these barriers and inundates houses and land. Successive Governments in Assam have spent nearly Rs 30,000 crore on building embankments over the last six decades. Tales of destruction every year are evidence of the ineffectiveness of these barriers.

Other man-made factors like deforestation, hill cutting, encroachments and destruction of wetlands have also worsened the flood situation. Embankments led to encroachment of river banks with an increasing number of people building houses and setting up establishments close to the river.

There has also been a population boom in the State which has put more pressure on the State’s ecology. The population density of Brahmaputra valley has increased from 9-29 people per sq. km. in 1940-41 to 398 per sq. km in the plain areas of Assam as per the 2011 census, according to a report by the Brahmaputra Board. The board under the Ministry of Jal Shakti monitors the Brahmaputra and Barak Valley and covers States under the Brahmaputra basin.

Climate change

Climate change is set to lead to more frequent and severe floods in Assam, as per a report on climate change by the State government. The report adds that extreme rainfall events will increase by 38 per cent. Heavy rainfall replacing continuous low or normal rainfall during monsoon combined with the melting of glaciers due to rising temperatures will mean that rivers from the Himalayas will be carrying more water and sediment even before they enter Assam where smaller rivers are swelled up due to incessant rainfall. This increases the possibility of frequent flash floods in low-lying areas.  

What is the way forward?

Once a necessity for farmland in Assam, floods have become a nightmare which return annually due to a combination of factors. The State’s unique topography, climate and socio-economic conditions make it more vulnerable to disasters like floods, with over one-third of the population living below the poverty line.

In a master plan on the river in 1982, the Brahmaputra Board suggested that dams and reservoirs should be built to mitigate floods. However, the construction of dams was opposed which led to the suspension of several projects.

The Water Resources Ministry of Assam focused on short-term measures like the construction of embankments to prevent the annual disaster. Successive Governments built embankments and repaired them after floods damaged or washed them away and the cycle continued.

A flood hazard atlas for Assam proposes non-structural measures to mitigate the impact of floods like flood forecasting and warning, flood profiling, and regulation of reservoirs. These measures, however, are yet to be translated on the ground.

The problem has now increased manifold and the impact of climate change is likely to aggravate the situation. With short-term measures proving inadequate,experts unanimously agree that long-term planning is the key.

One recommendation is to ensure that more credible information is made available so that preparedness can be improved and residents can be alerted. Further, experts have indicated that the region needs more institutionalised and technologically advanced systems to allow for credible and fast warning systems.

“Information should be available in local languages. With the forecast in, one can calculate how much more water will flow downstream, thereby alerting people in advance to evacuate. The nature of rivers is such that there is no way one can flood-proof the whole of Assam so one has to keep in mind that floods will happen,” Mr. Himanshu Thakkar of the South Asia Network on Dams, Rivers and People told The Hindu earlier.

A research paper published by the International Journal for Research in Applied Science & Engineering Technology says that wetlands and local water bodies should be revived in Assam to improve the drainage system, which can act as an exit for excess water and prevent waterlogging. “This would entail clearing human encroachments in the Brahmaputra flood plains. Embankments should be regularly checked for breaches and systems put in place for maintenance; a first step would be to break the babu-contractor nexus that finds floods an easy way to sponge money from the system,” the paper adds.

Watch | Why does Assam flood every year?
Flooding from the Brahmaputra and other rivers causes a deluge in Assam during the monsoon.


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Printable version | Jun 25, 2022 6:37:03 pm | https://www.thehindu.com/news/national/other-states/assam-flood-devastation-monsoon-brahmaputra-reason-cause/article65549836.ece