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Why do river channels change course in the Ganges delta?

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Physical map showing the Brahmaputra and Ganges river basins and their drainage networks across northern India, Bangladesh, Nepal, Bhutan, Tibet (China), and Myanmar. The map uses color shading to indicate elevation, from the high Himalayas in brown and white to lowland plains in green, and marks major rivers, tributaries, glaciers, dams, irrigated areas, and regions subject to flooding. An inset locator map highlights the region within South Asia. — Ganges River The Brahmaputra and Ganges river basins and their drainage network.

In the Ganges delta, river channels are constantly vulnerable to changes in their course due to the region's highly active geological and hydrological environment. These shifts are driven by several key factors:1

High Sediment Load: The Ganges-Brahmaputra system carries one of the world's highest volumes of suspended sediment. This rapid and continuous deposition of silt, sand, and clay leads to the constant formation of new lands, known as chars, and islands, which physically alter the landscape and force rivers to carve new paths.12
Erosion and Deposition: The land in the delta undergoes constant erosion and deposition. Because the rivers are active and carry such heavy sediment loads, they are rarely in the exact same location for two successive years.2
Monsoon Flooding: Seasonal monsoon rains cause extensive flooding, which can trigger sudden, dramatic changes in river courses. For example, major floods have historically diverted rivers into abandoned channels, fundamentally reconfiguring the local drainage network.2
Tidal Processes: The delta's growth and morphology are heavily dominated by marine and tidal processes, which influence how sediment is distributed and how channels are maintained or abandoned.31