# Boundary shear stress (for natural rivers)

## Description

Assuming a single, well-mixed, homogeneous fluid and a single acceleration due to gravity (both are good assumptions in natural rivers, and the second is a good assumption for processes on Earth, or any planetary body with a dominant influence on the local gravitational field), the only two variables that determine the boundary shear stress are the depth and the slope. For natural streams a typical useful relationship exists

Related formulas## Variables

τ_{b} | boundary shear stress (Pa) |

c_{units} | Unit conversion constant equal to 1 (kg/m^{2}*s^{2}) |

h | Depth of the flow (m) |

s | Lope (dimensionless) |