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Manning's equation is an empirical equation used to model Newtonian flow.

It was originally developed in the late 1800's to model flow in open channels; the classic equation is listed below.

Where:

is the flow velocity (m/s)

is Manning's roughness coefficient

is the hydraulic radius (m)

is the channel bed slope or friction slope (m/m)

The hydraulic radius is the ratio of the Flow Area to the Wetted Perimeter

is the hydraulic radius (m)

is the flow area (m²)

is the wetted perimeter (m)

In the Dam Beach Model Manning's equation is used to estimate the friction slopes in the and directions.

The friction equations as implemented are listed below.

Where:

is the friction slope in the direction

is the friction slope in the direction

is Manning's roughness coefficient

is the velocity in the x direction

is the velocity in the y direction

is the flow depth

The only input is , Manning's roughness coefficient.