Tsangpo megafloods

**Figure 1.** Map of Tibet and Bengal basin showing the locations of ice-dammed lakes that formed when Himalayan glaciers blocked the Yarlung-Tsangpo River in Tibet.

**Figure 2.** Potential magnitude of flood depth (shading) given the amount of water in a glacial lake outburst flood (GLOF) event (on the y-axis) and a parameter relating to the roughness of the topography the flood was flowing over (x-axis) for four locations (transects) along the Brahmaputra-Jamuna River valley.

There is a tale told around the Yarlung-Tsangpo River in Tibet that ~1,200 years ago, the Buddhist master Guru Rinpoche defeated a lake demon and cleared the area for settlement. As it turns out, there is geological evidence that a glacially-dammed lake burst catastrophically at that exact time. Such glacial lake outburst floods (GLOFs) may have occurred many times and could have played a major role in sculpting regions of the Himalaya as well as the Bengal delta region downstream. Similar phenomena occurred throughout the world during the last Ice Age, including the Lake Missoula megafloods that carved out the Channeled Scablands of eastern Washington. Our work suggests that these megafloods could have sculpted the large, boulder-paved “paleovalley” that lies under the present day Brahmaputra-Jamuna River.

For more information, check out our paper in the Geological Society of America Bulletin:

Pickering, Jennifer, M. Diamond, S. Goodbred, C. Grall, J. Martin, L. Palamenghi, C. Paola, T. Schwenk, R. Sincavage, & V. Spieß (2018). Impact of glacial-lake paleofloods on valley development since glacial termination II: A conundrum of hydrology and scale for the lowstand Brahmaputra-Jamuna paleovalley system. The Geological Society of America Bulletin, 131(1-2), 58-70, doi:10.1130/B31941.1