# Surface flow formula (Water Overlay)

Imbalances in water levels across the grid drive the flow of water until a state of equilibrium is reached in terms of *h* (the height of the water column) and flux. Behavior of the flow is described by a second-order semi-discrete central-upwind scheme produced by Kurganov and Petrova (2007)^{[1]}, which is based on the 2-D Saint-Venant equations (a.k.a. shallow water equations):

where

*u*is the velocity in the *x*-direction*v*is the velocity in the *y*-direction*h*is the water depth *B*is the bottom elevation *g*is the acceleration due to gravity *n*is the Gauckler–Manning coefficient

## See also

## References

- ↑ Kurganov A, Petrova G (2007) ∙ A Second-Order Well-Balanced Positivity Preserving Central-Upwind Scheme for the Saint-Venant System ∙ found at: http://www.math.tamu.edu/~gpetrova/KPSV.pdf (last visited 2019-04-11)