Susannah Does Science!
Evidence for periodic natural dams (and floods) in the eastern Himalaya
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
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
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.