And That's How ENO Was Born

The first ENO (essentially non-oscillatory) method was developed by Harten, Engquist, Osher and Chakravarthy in 1987.
ENO reconstructs a piecewise smooth polynomial function from cell averages. In CFD applications: mass, momentum and energy are conserved; in our case, the sand is "conserved" ---- it is just being shoveled around to make the land smooth, no increase nor decrease in the amount of sand!