Why understanding the Brahmaputra river basin provides a better insight into the yearly floods in Northeast India and Bangladesh

by Nibedita Saha

Monsoon has been one of the most romanticized weather among people. Monsoon reminds us of love and cozying up to our loved ones with endless conversations, plates full of pakoras and warm cups of tea. But monsoon has a very different meaning for the people of Northeast India and Bangladesh.

Over the years, floods in the Brahmaputra river have displaced millions of people in Northeast India and its neighboring state Bangladesh. And, every year people move on calling it an “annual phenomenon”. 

But this annual phenomenon has several volatile factors in nature that push the problem to become worse. Northeast India is vigorously dominated by monsoon as most of its districts are located near the Brahmaputra river– comprising mainly of basins of three of the large river systems of the world–the Brahmaputra, the Barak (Meghna) and the Irrawady, which makes the region one of the most flood-prone state in the country.

Since the monsoon hit the Northeastern part of India alongside Bangladesh in May, more than 300 people have lost their lives. So before going into the grime situation of flood-affected people in both countries, let’s understand the Brahmaputra River basin.

Understanding the Brahmaputra River basin

It is the lower Brahmaputra River in Northeast India and Bangladesh that floods every year during June-September, the summer-monsoon months, taking the lives of hundreds and affecting millions in both the countries.

As many as 32 districts out of 36 in the state of Assam suffered due to the floods every year including Bajali, Cachar, Chirang, Dibrugarh, Dima Hasao, Golaghat, Hailakandi, Hojai, Kamrup, Karimganj, Morigaon, Nagaon, Sivasagar, Tezpur, Tamulpur and others. 

And in Bangladesh too, the picture is similar to worst with more than 64 flood-affected districts including Sylhet, Sunamganj, Hobigonj, Moulvibazar, Mymensingh, Netrokona, Jamalpur, Sherpur, Rangpur, Panchagarh, Nilphamari, Lalmonirhat, Kurigram, Thakurgaon, Dinajpur, Gaibandha and others.

All these districts in both the countries have one thing in similar besides it floods every year in these region—that is all of them are located on or near the shores of Brahmaputra river, also called Jamuna in Bangladesh.

Route of Brahmaputra

The Brahmaputra is the ninth longest river in the world which originates from Angsi Glacier in the northern side of Himalayas in Tibet, known as Yarlung Tasangpo that flows eastward parallel to the Himalayas taking a U-turn at Namcha Barwa making its way to the south in Arunachal Pradesh, where it is knows as Siang/Dihang river.

From Arunachal Pradesh, it flows down to the southwest in Assam Valley and continues to flow through the valley entering into Bangladesh finally meeting the Bay of Bengal. Brahmaputra basin is one of the ‘most’ disaster-prone basins in the world as it receives the heaviest rainfall in the world. 

Brahmaputra basin span across Arunachal Pradesh, Assam, Sikkim, West Bengal, and Meghalaya in India—in which Assam is the most floods prone as Sikkim and Arunachal gets a snow cover. Majuli district, the river island in Assam marks the largest mid-river delta system and also of the badly affected districts.

According to National Commission on Floods, around 40% of Assam’s land-31.05 lakh hectares of the total 78.5 hectares- is prone to floods. The Brahmaputra travels a length of around 650 km and 80% of the annual rainfall in the Brahmaputra basin takes place during the monsoon months, according to the Water Resource Ministry of Assam.

As the river flows down from Trance Himalayas at an elevation of over 5,000 m, the river carries a higher amount of sediment while it enters Assam. According to studies an average slope of about 2.89 m/km comes down to about 0.1 m/km leading to flattening of the slope that causes a sudden drop in velocity which deposits huge quantities of sediment and other debris leading to the rise in water level of the river.

This highly sedimented river water from Himalayan terrains combines with rain-fed 41 major tributaries—26 in the north bank and 15 in the south banks leading to destructive floods every year.

Meanwhile, an increase in construction activities in the valley, alongside climate change and Assam being in a seismically active zone, leads to frequent landslides that contribute in raising the riverbed by depositing sediments and debris in the river. 

Situation in Assam and other Northern parts of India

The Northeast India, consisting of eight states–Arunachal Pradesh, Manipur, Assam, Meghalaya, Nagaland, Mizoram, Sikkim and Tripura–presents a particular geophysical unit set located in the Eastern Himalayan Region.

The region is enriched with a sub (extra) tropical type of monsoonal climate, hence it shows remarkable variability of weather and climate on a regional scale. According to studies, Northeast India possesses about 30% of the total water resources potential and about 41 % of the total hydropower potential of India.  

During the 2022 floods in Assam, the situation has been not so different from every year, it has havocked the state affecting millions of people.

Current situation

According to an official bulletin, more than 29 lakh people in 30 districts remain affected as of 2nd July.

As of July 21st, a total of 197 people have lost their lives in Assam floods and landslides this year. The Assam State Disaster Management Authority (ASDMA) reported on the same day that six revenue circles and 56 villages in five districts were still under floodwaters.

One of the worst affected districts was Cachar and Silchar. Whereas over nine thousand people were suffering from the flood in Chachar, in Silchar 80% of the city was underwater.  The other affected districts of the state are Tinsukia, Dima Hasao, Tamulpur and Morigaon.

This year, Assam was crippled in two waves of flood, one in May that majorly affected parts like NC Hills, Barak Valley and Hojai and then again in June, which wrecked most of Lower Assam along with Barak Valley.

Even though the situation has improved in recent days, where no death has been reported and the number of flood-affected people have come down to 10,000 in three districts only. According to ASDMA’s official bulletin of July 23, the worst-hit district is Cachar with over 6,600 people suffering from the deluge followed by Morigaon (2,600), and Tamulpur (900). Presently, 44 villages are under water and 210 hectares of farmland have been damaged, said the bulletin.

This year the flood was more devastating as people were still struggling with the COVID pandemic. The floodwater washed away not only home, it also destroyed roads, bridges, embankments and other infrastructures in the state. Many embankments were breached in Cachar, Udalguri, Baksa and other districts while 486 roads and 14 bridges have been damaged.

According to the ASDM Flood Report of June 19, 2022, a total of 297 embankments have been breached in 20 districts of Assam, with 33 in Darrang alone.  

“A crop area of 63314.75 hectares has been inundated while 795 animals were washed away and 9,55,089 were affected,”, it further added.

Currently, no river is flowing above the danger level in the state, the bulletin said.

Situation in Bangladesh

The northwestern part of the country experience floods every year as this part of the country boarding Indian State Meghalaya receives above normal rainfall. But, 2022 was more devastating as it havocked the country in parts of flood waves. The Sylhet region has alone taken to toll with more than 7.2 million people suffering. People lost their paddy fields, fish ponds, and livestock in the disastrous flood. Besides Sylhet district, Sunamganj and Netrokona districts were among the most affected following Moulvibazar, Habiganj, Kishoreganj, Brahmanbaria, Sherpur and Mymensingh.  

More than 100 deaths have been reported in 27 of the 64 flood-affected districts in Bangladesh between May 17 and June 28. Just like India, Bangladesh too witnessed floods in two parts—one hit the country on May and the second came in July.

This year, most deaths were reported due to drowning, snake bites and lightning in the flood-hit areas said the report. The floods in Bangladesh not only caused death and destruction but also triggered post-flood emergencies including drinking water crisis, health and rehabilitation.

The major fear is waterborne diseases due to lack of clean water. Atiqul Haque, director general of the Department of Disaster Management in Bangladesh showed his concerns over an outbreak while speaking to Reuters.

Haque added that ensuring the availability of drinking water is the top priority for the government,

“With the flood waters receding, there is a possibility of an epidemic. We fear the outbreak of waterborne diseases if clean water is not ensured soon,”

Haque also informed that more than 4,000 people have contracted waterborne illnesses, including diarrhea, in flood-hit districts. People are mainly suffering from diseases like diarrhea, dysentery, fever, skin infections and other waterborne diseases.

As of July 21, 16,469 cases of waterborne diseases and other ailments have been reported, according to the UNICEF Bangladesh Humanitarian Situation report.  

Role of Climate change

The “annual phenomena” of flooding in the Northeastern part of India and bordering the state of Bangladesh is majorly attributed to climate change. Still, human-made unplanned developments too play a pivotal role in inviting disasters.

Floods in the two river basins of Brahmaputra and Barak have caused unprecedented destruction in recent years indicating mismanaged flood control measures, shrinkage of water-bodies, population pressure, unregulated construction and skewed development strategies.

Excess rainfall

Assam and entire Northeast India and parts of northwestern Bangladesh is one of the highest rainfall zones in the world due to their geographical and topographical region.

In recent years, the region has received approximately double rainfall. So far in June, Assam has recorded an excess rainfall of 109%, according to the India Metrological Department. The State received 528.5 millimeters of actual rainfall against the normal 252.8 millimeters in June.

According to the World Weather Attribution, global warming has made extreme rainfall more common and more intense across most of the world. It also predicted that “climate change, together with urbanization and housing patterns, will further aggravate the risk of flooding in the coming years”.  

World Weather Attribution is a network of scientists tracing the impact of climate change.

Roxy Mathew Koll, a climate scientist with the Indian Institute of Tropical Meteorology, explained how global warming leads to excessive rainfall said,

“These strong monsoon winds in the Bay of Bengal can now carry much more moisture than ever before, in response to global warming”.

As the temperature rise, the volume of atmospheric moisture also increases because warmer air holds more moisture and for a longer time, explained Koll. “Hence, the large amount of rainfall that we see now might be a climate change impact.” 

These winds dumping rains over Bangladesh and northeast India have been exceptionally strong for a week now, the scientist added. About 3.5 million of Bangladesh’s 160 million people are at risk of river flooding every year, according to a 2015 study by World Bank Institute.

Studies have found that rains are getting more unpredictable and many rivers are rising above dangerous levels more frequently than before.  

Saiful Islam, Director of the Institute of Water and Flood Management at the Bangladesh University of Engineering and Technology, cited one of his research papers while speaking to Aljazeera said,

“even if average global temperature increase modestly–by 2 degrees Celsius over the average of pre-industrial times—flooding alone the Brahmaputra river basin in northeastern India and Bangladesh is projected to increase by 24%.”

Besides heavy rainfall causing floods in Assam, landslides also took many lives and human-caused disturbance played a big role. According to Rashtriya Barh Ayog’s (National Flood Commission) calculation, 39.58% of the total area of the state is flood-prone and it also presents 9.40% of the total flood-prone area of the country.

Human interventions

As far as Bangladesh is concerned, climate experts believe that the flood was destructive this year as a high volume of rainfall has remained stuck in the Haor region of Sylhet and Netrokona district as the 124km passage for discharging stormwater from Cherrapunji in India to Bhairab in Bangladesh has been destroyed due to human intervention.

Experts claimed that the recent development of All Weather Road, connecting the three Haor regions—Itna, Mithamoin and Ashtagram—has blocked the drainage passage.  

Another environmental scientist Dr Partha Jyoti Das explained the condition in Assam and said,

“Growing population and construction in flood-prone areas are some of the reasons behind the burgeoning damage in the state.”

Das was speaking to PTI, an Indian news agency, further said “in several places, breach of embankments has caused widespread destruction. Add to that, frequent flash floods leave people with little time to protect life and property.”

He further added,

“Drainage congestion in low-lying areas, which is a result of rapidly changing land use practices, fast pace of urbanisation and expansion of human habitat all around, at the cost of natural waterways, have also intensified the flood situation.”

Engineer J. N. Khatanair, the technical advisor of Guwahati Metropolitan Development Authority (GMDA), in one of his statements to the media said that ‘unplanned city growth due to heavy human influx with uncontrolled construction activities are the main reason behind flood in Guwahati.

“The present flood experienced in Guwahati is human-caused. Massive unauthorised human habitation taking place in the hill area with deforestation haphazardly taking place has also played a major role in aggravating the flood situation in the city,” he said.

Another climate expert, Bhupen Goswami, former director of the Indian Institute of Tropical Meteorology (IITM) though attributed to climate change as a factor contributing to the heightened impacts of the extreme event but also recognized that these annual phenomena of flooding in Assam also a result of bad management of dams.  

Goswami was speaking to Mongabay-India, said,

“Earlier, if extreme weather events were happening every 100 years, then now maybe they will happen every ten years. But floods in Assam are also a result of bad management of dams,”

He further added,

“The flood which is affecting Barpeta and other places of Lower Assam is because of water released from dams in Bhutan and the impact was aggravated by the heavy rain. The meteorological community gave a good forecast this year that there are going to be intense spells of rain. So, keeping that in mind, the release of water from dams should have been planned better,”

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