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.

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

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, $t_{c}$ should be multiplied by 0.2.

Related Topics

• Computing Lag Time or Time of Concentration from Basin Data