Numerical Simulation and Model for Channel Levee Formation

Birman, Vineet¹, Brendon Hall¹, Nicolas Guillaume², Eckart Meiburg³, Ben Kneller⁴ (1) University of California at Santa Barbara, Santa Barbara, CA (2) Ecole Nationale Superieure d'Arts et Metiers, 75013 Paris, France (3) University of California at Santa Barbara, Santa Barbara, (4) University of Aberdeen, Aberdeen, United Kingdom

Submarine channel levees are formed by deposition of sediment from channel overflows. The shapes of the levees vary, but thickness decay away from the channel can be approximated by power law (for channels on higher gradients) or exponential decay (low gradients).

We provide a simple analytical model to describe the levee shape as determined by the flow parameters. In our model we assume that levees form due to a steady continuous overflow of a suspension of mono-disperse particles. We derive the conservation equations for particles, fluid and momentum. These equations can be solved analytically for some simple cases and valuable insight into more complex cases can be obtained. We find that entrainment has an important effect on the shape of the levee.

We consider a channel cross-section and perform two-dimensional numerical simulations of the Navier-Stokes equations to examine the formation of levee in more detail. The interstitial fluid in the turbidity current is assumed to have same density as the ambient. The density difference is entirely due to particle concentration in the turbidity current. Particle concentration is kept constant at the channel center. A proportion of the particles transported by the flow are deposited on the levee. This flow attains a steady state as it loses particles due to deposition and the steady state deposit profile determines the shapes of the levee. We discuss the entrainment in the numerical simulations and the deposit profiles thus obtained for different grain sizes. We compare the steady state results with our analytical model.