SIMPLY PUT: Why Assam gets flooded every year

The pre-monsoon season hasn’t started on a pleasant note for Assam. Every year, the rainy season brings destruction to the most-populated northeastern state. It brings chaos, displacing thousands of people and animals, and damaging crops and properties worth billions.

However, this time, the monsoons are yet to arrive and according to the Assam State Disaster Management Authority (ASDMA), at least 4 lakh people have been affected and 24 people have lost their lives so far due to the floods which have ravaged the state.

On May 24, Assam floods witnessed a surge in the death toll, as it rose to 25 and 6.5 lakh people remained affected. These 6,50,402 affected, which include 1,25,471 children, reside in 1,709 villages based in 22 of the state's 34 districts. Close to 82,503 hectares of crop areas in flood-hit areas also remain affected.

Why are floods an annual occurrence in the state of Assam?

Assam is one of the most flood-prone states in India and it has almost become an annual calamity. In terms of impact on human lives, the floods of 1988, 1998 and 2004 were the worst – the 2004 floods alone affected 12.4 million people and claimed 251 lives.

According to the Assam government, the flood-prone area of the state is 31.05 lakh hectares, against a total area of 78.523 lakh hectares – this means nearly 40% of the state’s area is flood-prone.

Overall, Assam accounts for nearly 10% of the total flood-prone area of the country.

The average annual loss due to floods in Assam is to the tune of ₹200 crore and particularly in 1998, the loss suffered was about ₹500 crore and during the year 2004 it was about ₹771.00 crore.

Apart from the natural topography and annual excessive rainfall in Assam, there are various reasons – both man-made and natural – behind the destructive floods that hit Assam every year.

Assam is home to a vast network of rivers, including the Brahmaputra and Barak River, and more than 50 tributaries feeding them. Assam also receives river water from neighboring states like Arunachal Pradesh and Meghalaya.

In 2004 and 2014, the south bank tributaries of the Brahmaputra in lower Assam experienced flash floods of high magnitude due to cloud bursts in the catchment areas in Meghalaya. A similar incident occurred in Arunachal Pradesh in 2011, further aggravating floods in Assam.

Bank erosion caused by the river Brahmaputra is one of the major reasons why Assam gets flooded every year. It means the removal of soil, sediment, or rock fragments along the banks, which results from high water flow.

Due to erosion, the width of the river increases and it changes its course. According to the Assam government, more than 4.27 lakh hectares of land, which is 7.40 % area of the state, has been eroded by the river Brahmaputra and its tributaries since 1950.

The width of the river Brahmaputra has increased up to 15 kilometres at some places due to bank erosion, making it the widest river in India. It is estimated that annually nearly 8,000 hectares land is lost to erosion.

The surveys carried out at different periods reflect an alarming picture regarding the widening of river Brahmaputra which is as follows:

Floods are also caused by human intervention – like encroachment of river banks and wetlands, lack of drainage, unplanned urban growth, hill cutting and deforestation. The dams that are being built are further aggravating these disasters.

Government measures to control floods in Assam

In 1982, the Brahmaputra Board suggested that dams and reservoirs be built to mitigate floods in Assam. While dams are meant to regulate the flow of water, they can also be beyond the capacity of the channels downstream, proving to be a double-edged sword.

The Water Resources Department of Assam has constructed embankments and flood walls across the state. River training, bank protection, anti-erosion and town protection are also in the works. Here’s how their plan has progressed thus far:

Here's a short video