On December 25, Prime Minister Narendra Modi inaugurated India’s longest road and rail bridge in the northeastern state of Assam. The bridge is being hailed as a Modi government achievement ahead of next year’s elections, but a darker side to the bridge has so far been ignored.

Bogibeel Bridge is the fourth span over the Brahmaputra River that connects Dhemaji and Dibrugarh, Assam’s two easternmost districts. It’s also the first bridge to upper Assam, where people have long called for a link to connect the underdeveloped Dhemaji with Dibrugarh, one of the state’s richest districts.

On the positive side, the 4.9-kilometer Bogibeel Bridge will drastically reduce the travel time between Dhemaji and Dibrugarh. It will also provide the people of Dhemaji with access to better healthcare, education and many more facilities in Dibrugarh without them having to make long or precarious journeys by boat or buses.

The bridge has been opened after more than a decade of delays. During this period, it was initially seen as a source of hope for people before it became a subject of ridicule. Approved in 1997-98, it was not until 2002 that construction kicked off, during the first National Democratic Alliance under the late Atal Bihari Vajpayee.

While it may seem like a comfortable narrative of infrastructural achievement for the ruling Bharatiya Janata Party, it came a huge price. The cost of the project jumped more than 70% over the 16 years it took to build, from Rs 17.67 billion (US$252 million) in 2002 to Rs 60 billion on completion.

But, almost every year Assam is affected by floods, as the Brahmaputra and its tributaries overflow due to various natural and man-made causes. There are concerns that the Bogibeel Bridge could exacerbate those problems and affect people living in downstream areas.

Risk of flooding, erosion

The construction of the bridge will lead to a narrowing of the river. People in Assam often refer to the Brahmaputra as a moving ocean due to its considerable width: 10.3 kilometers wide between Bogibeel and Kareng Chapori, the two sides of the bridge. In order to construct this bridge, the width was reduced to 4.9 kilometers by creating approach embankments in the riverbed. While this has channeled the flow of the river under the bridge, it has also resulted in submergence of villages outside the Sissi-Tekeliphuta dyke in the immediate downstream of the bridge.

However, the downstream impacts are not just limited to that. This shrinking of the river also poses a threat to the existence of further downstream areas including the world famous Majuli island and the flood-vulnerable Matmora area in Lakhimpur district.

In 2006, the Assam Legislative Assembly discussed the “Majuli Cultural Landscape Region Bill”, which noted the threat that Bogibeel Bridge poses to Majuli Island. “Four years before construction of the Bogibeel Bridge a report was sent saying that a four-kilometer-long bridge was proposed in the Brahmaputra. If this happens water will overflow in the downstream areas. In this situation, the lower side will become erosion free but the upper side will suffer from increasing erosion,” the bill said.

These concerns about the bridge led to the setting up of the Majuli Suraksha Samity (Majuli Protection Committee), a local NGO, which demanded feasibility studies of the impact that the bridge might cause in Majuli, Dhemaji and Lakhimpur districts.

This was spurred by earlier experiences after three previous bridges were built on the river. Areas immediately downstream suffered unprecedented flooding and erosion.

An article titled “Contending Water Uses: Bridge over the Brahmaputra” noted this concern. It said areas that suffered negative impacts were Palasbari and Gumi, downstream of the Saraighat Bridge; Morigaon and Nagaon regions downstream of the Koliabhomora Bridge; plus Dakhin Salmara, Pancharatna and Mancachar areas downstream of Naranarayan Setu.

The narrowing of the river at Bogibeel is expected to increase the velocity of the river, which is known for its strong current. And this is likely to affect areas downstream that have a long history of flood and erosion, increasing their vulnerability.

The village of Matmora in Dhakukhana subdivision has borne the brunt of river erosion for more than three decades. In 2010 the national government spent Rs 1 billion building the 5km Matmora geo-tube embankment as part of the Sissikhalgar-Tekeliphuta dyke. But it is not known yet if the geo-tube embankment has been effective in protecting Matmora from erosion. And now there are fears that increased river velocity due to the construction of the Bogibeel Bridge will directly affect the Matmora embankment, making it more vulnerable to erosion.

The building of embankments to protect areas from floods and erosion has been critical to help villagers survive throughout Assam. But some say spending money on bridges is like putting money in a bottomless pit – it may give a measure of investment, but the emotional cost and vulnerability remain for villagers in some areas.