WMS:Ramser Tc Equation

Ramser (1927) developed an equation for computing the time of concentration in well-defined channels. The equation is based on the length and slope of the channel.

$t_{c}=0.008L_{c}^{0.77}S_{c}^{-0.385}$

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where:

t_c - time of concentration in minutes.

L_c - length of channel reach in feet.

S_c - average channel slope in ft/ft.

For flow in concrete channels, tc should be multiplied by 0.2.

Related Topics

• Computing Lag Time or Time of Concentration from Basin Data