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Evidence for periodic natural dams (and floods) in the eastern Himalaya

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Megafloods sourced from glacial lakes on the Tibetan Plateau have been proposed as agents of massive geomorphic change along the Yarlung-Siang-Brahamaputra River. Over 300 ancient and historic landslide and glacial dams have been identified in the region. These observations along with depositional evidence of catastrophic downstream flooding from dam failure show outburst floods of different magnitudes have likely influenced this mountain landscape throughout the Quaternary period (2.58 Mya), with effects extending beyond the Himalayan range through the Bengal Basin and >2000 km offshore in the Bay of Bengal.

eastern Himalayan megafloods

Some examples of what GeoClaw results look like.

GeoClaw uses the 2D depth-averaged shallow water equations for flow over varying topography. Typically used for tsunami modeling, GeoClaw can capture the wet/dry boundary as a wave propagates over dry topography. It conserves volume and refines using a block structured adaptive mesh refinement (AMR). That's the pixelization you see below.

In each of the following videos, each frame represents one hour within the the model.

Depth (m)
Speed (m/s)
Bed Shear Stress (Pa)
Results near Tuting.
Bed Shear Stress
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Bed shear stress colorbar is scaled to the shear stress required to initiate motion on a grain size given the local channel gradient.

Flood Power
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Flood power is calculated as the velocity times the bed shear stress. It's colorbar is scaled to results from Denlinger and O'Connell (2010) which observed megaflood erosional features at flood powers >10 kW per square meter and megaflood erosional features at flood powers < 5 kW per square meter.

As an earth scientist, it is my responsibility to acknowledge that the space I occupy in Colorado is the ancestral lands where the Native Americans, the Arapaho, Cheyenne, Comanche, Plains Apache, and Ute have a familial connection and relationship to this land. S/he is their grandparent, their mother, who has provided for them and for us, and who we are obligated to care for in return.

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A meaningful Land Acknowledgement must address historical wrongs and inequities, not just the fact that others once occupied the land. As a new resident of Colorado, I am beginning learning about history of this land and these Peoples. Below is the University of Colorado Land Acknowledgement, which I will refine once I know more.

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The University of Colorado Boulder, Colorado’s flagship university, honors and recognizes the many contributions of Indigenous peoples in our state. CU Boulder acknowledges that it is located on the traditional territories and ancestral homelands of the Cheyenne, Arapaho, Ute and many other Native American nations. Their forced removal from these territories has caused devastating and lasting impacts. While the University of Colorado Boulder can never undo or rectify the devastation wrought on Indigenous peoples, we commit to improving and enhancing engagement with Indigenous peoples and issues locally and globally.

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