Teesta Bazaar vulnerable to future water surges as riverbed rise after GLOF

GANGTOK, : Increased sediment and silt deposition have seen Teesta River bed increase by 6-7 metres in Teesta Bazaar area after the 2023 GLOF, with experts expressing concerns that the settlement is more vulnerable to flooding.

Teesta Bazaar is a vital route to connect Sikkim and Kalimpong with Darjeeling-Kurseong region, and is located on the right bank of Teesta River while NH 10 runs on the left bank. It falls under Kalimpong district.

According to a Jal Shakti Ministry-appointed committee, deposits have forced Teesta River to expand on both banks and the rightward channel shifting near settlements.

“At this downstream location in West Bengal, the riverbed has risen by 6–7 meters post-GLOF. The channel has also widened significantly towards the right bank. This indicates that sediment from upstream found its deposition base here, where the valley opens and gradient further reduces,” said the committee in its report of April this year.

During the 2024 monsoon, the first monsoon after the GLOF, Teesta Bazaar had been flooded with rising water levels of Teesta River which submerged some houses there. Local residents, settled close to the river, took shelter in the houses of their relatives or community halls. As the water level rose, the road from Sikkim and Kalimpong via Lopchu-Peshok was also closed for a long period with the road stretch at Teesta Bazaar submerged under water.

As per the Jal Shakti Ministry’s committee, increased sediment and silt deposition have caused a rise in the riverbed level, leading to concerns about potential flooding and making the Teesta Bazaar area more vulnerable to future water surges.

Besides Teesta Bazaar, the Melli region is also vulnerable to flooding as the Teesta River bed rose by nearly 14 m due to heavy siltation after the GLOF 2023.

The Central committee was tasked to assess the morphological impacts caused by the GLOF on Teesta River and to propose remedial measures. The committee members along with officials from Sikkim and West Bengal governments conducted site visit from July 15, 2024, to July 19, 2024 covering the problem areas in Sikkim and West Bengal.

In its report, the committee recorded that the GLOF incident triggered significant geomorphological changes along the Teesta River in Sikkim and parts of West Bengal. The study is crucial as NH 10 – the lifeline of Sikkim – runs alongside the Teesta River.

Key findings highlight differential river behavior, erosion dominating the upper steep reaches and heavy sedimentation in the lower flatter segments. Satellite imagery and cross-sectional analysis confirmed major sediment deposition, lateral shifting, and changes in channel morphology.

These impacts are most pronounced in Mangan, Dikchu, Singtam, Rangpo, Melli, and Teesta Bazar stretches of Teesta River.

The study recommended a cautious and phased approach to river management: allowing natural stabilization in less critical zones while prioritizing targeted river training works, catchment treatment, and floodplain zoning in vulnerable areas.