Himalayan disaster explained The Rishi Ganga River rises in the shadow of Nanda Devi (7,816m), India's second highest mountain. Credit: Sumod K Mohan / Wikicommons A devastating flood last week on the upper reaches of the Rishi Ganga River, in India’s northern state of Uttarakhand, is a stark warning of the hazards of hydropower development under the dual threats of climate change and young, unstable mountains, scientists said last Friday in a webinar hosted by the The Earth Institute at Columbia University, New York, US. The flood came thundering down the Alaknanda River, a Ganges River headstream, and hit two dams (one still under construction), smashing both and killing dozens of people, including construction workers caught unawares at the second dam site.