When Rivers Change Their Minds

India's Prime Minister Manmohan Singh has described the flooding as a national calamity.

When the swollen Kosi river burst its banks in Nepal just north of the Indian border, it changed course, flowing through a fresh channel 75 miles to the east that has no protective embankments.

The river traditionally swells to a flood peak in October.

In 2007, monsoon floods killed more than 2,200 people across South Asia and left 31 million others homeless, short of food or with other problems. The United Nations called last year's floods the worst in living memory.