where D is the depth, and K is the yield strength.
Bingham Plastic Model, Yield Strength
References
McEwen, A. S.; and Malin, M. C. "Dynamics of Mount St. Helens 1980 Pyroclastic Flows, Rockslide Avalanche, Lahars, and Blast." J. Volcanol. 37, 205-231, 1989.
