The people of Assam have lived with floods for centuries, but they have never been as surprised by its timing, intensity, and extent as they are now. The recent flooding of the riverine island of Majuli and the three waves of floods already in 2024 are testimonies to the changing character of flooding in the riparian state over the past 50 years, especially along the Brahmaputra river.

“The flooding in Majuli was sudden and occurred due to the combined impact of the rising water of the Brahmaputra river and the gushing water from its tributary, the Subansiri,” Partha Jyoti Das, head of climate and water hazards at non-profit Aaranyak, told Down To Earth.

Such flash flooding is more dangerous for people in the impacted area than a normal flood and is new for many of these areas, according to Das.

The flash flooding in the Subansiri was because of heavy rainfall in Arunachal Pradesh, from where the river flows steeply into Assam, Das explained. This added to already rising water levels in the Brahmaputra. The volume of water was such that a well-built and maintained embankment in the western part of Majuli breached at its weakest point.

There has not been a lot of flooding in Majuli for the past 4-5 years, so people were caught off-guard. “People may have had a false sense of security about the strength of the embankment. Also, the fact that it is normal for the water levels in both the Brahmaputra and the Subansiri to increase and decrease throughout the monsoon season,” said Das.

The increased extreme rainfall and occasional cloud bursts in Arunachal Pradesh and even in Meghalaya are responsible for flooding in Assam, in addition to the rainfall within the state. Heavy rainfall in Bhutan's hills often leads to flooding in the western part of the state.

The northern parts of the state flooded due to excessive rainfall in Arunachal Pradesh, while some southern parts, such as Guwahati, flooded by heavy rainfall on the northern slopes of the Meghalaya hills. In 2004 and 2014, southern districts like Kamrup and Goalpara flooded due to cloud bursts in the Garo hills, Das pointed out.

Majuli is just one example in Assam's saga of living with floods. The most recent flooding season for the state began on May 28, caused by rainfall from the remnants of Cyclone Remal.

By June 2, 13 districts of the state were flooded, with three people losing their lives in flood-related incidents, 535,000 people affected and 8,144 hectares of crop area inundated, according to data from the Assam State Disaster Management Authority (ASDMA).

There was some rainfall after the cyclone dissipated, maintaining flooding in some districts until June 15. On June 16, rainfall intensified again, and a second wave of floods hit many districts.

The peak of this wave of floods was reached on June 20 when 1,311 villages across 22 districts were inundated. On that date, 409,000 people remained impacted by the flooding and 6,425 ha of crop area were affected, according to ASDMA data.

This flooding see-sawed until June 29 when seven districts of the state were still reeling under floods. From June 30, the third wave of floods spread to 29 of the state’s 35 districts in just three days by July 3.

“Forty-six people have died in different flood-related incidents in the state,” according to media reports. The number of affected people in 2,800 villages has reached 1.625 million, and 39,452 ha of crop area lies devastated, according to ASDMA data on July 3.

Of these, 25,744 people are in relief camps, while 361,000 people are in relief distribution centres. Almost 500,000 people were added to the flood-impacted list in just one day between July 2 and July 3.

The rainfall in Assam during the current monsoon season from June 1-July 3 exceeded the average by 18 per cent, which the India Meteorological Department (IMD) considers normal.

“There are at least 4-5 waves of floods every year in Assam, but in some years, the season gets elongated. This is happening more frequently now and last happened in 2022,” said Das.

In 2022, most of the state had seen multiple waves of floods by June. Then there was a long dry period in July and August, and rains picked up again in September and October, bringing back the floods. This is the worst-case scenario for Assam's farmers, who mostly grow paddy for their sustenance.

“The early rains in April, May, and June 2022 meant that they were not able to sow their seeds. Then, in July and August, most of the farmers who managed to sow their seeds kept waiting for the rains to water their fields. And once it was time for harvest, the floods brought back the misery,” said Das.

When the rains cease, there is a lull for some time, and floods concentrate in certain pockets. Then, as the rainfall starts again, these pockets expand rapidly and inundate other areas.

“Even then, the persistence of floods in Assam has decreased over the past 50 years, though the short-term aggression has increased. In the 1980s, many areas would be under flood waters for long durations, for weeks and even months,” said Das. Now, he points out, the flooding is quick and, in some sense, more devastating.

In the last 50 years, major floods have occurred in Assam in 1972, 1974, 1978, 1983, 1986, 1988, 1996, 1998, 2000, 2004, and 2012, according to the ASDMA. Since then, there have been quick flash floods every year and long-term inundations in some years such as 2018, 2020, 2021, 2022, and now in 2024.

“There was a predictability to the flooding which is absent now. There are also some new areas, such as Dima Hasao and Karbi Anglong, which were never known to get flooded before but are experiencing floods now,” said Das.

Due to the suddenness of the floods, people have also lost their adaptive capacity to face and live with the floods. In some areas, the sense of security that comes from embankments has made people less prepared for the kind of flash flooding that happens now.

“They often don’t realise that no embankment is going to last forever against the fury of the river. The changing rainfall patterns, especially the extreme rainfall and cloudbursts in the hills, and the land use changes are only making the rivers more aggressive,” Das quipped.

A detailed reassessment of the flooding situation in Assam needs to be carried out, taking into account the changing climatology, land use patterns and socio-economic makeup of the state. And adaptation technology, such as embankments, including the materials used in them, needs to be designed using this reassessment, according to Das.