Major rivers can suddenly jump into new channels

A river might seem like a permanent fixture on a map, but in deltas like the Mississippi or the Ganges-Brahmaputra, the water is actually engaged in a slow-motion climbing act. As these rivers carry sediment downstream, they drop mud and sand onto their own floors, gradually raising the riverbed until the water is flowing several meters above the surrounding floodplain. This precarious setup creates a geological tipping point. During a particularly heavy flood, the water can burst through a bank and find a steeper, faster route to the sea, abandoning its old channel entirely in a violent process known as an avulsion.