WMS:Riverside County Lag Time Equation

The Riverside County Flood Control and Water Conservancy District developed three different lag equations corresponding to mountainous, foothill, and valley areas near Riverside County, California (Anonymous, 1963).

$T_{LAG}=1.20\left({\frac {L\ast L_{ca}}{\sqrt {S}}}\right)^{0.38}$

(Mountainous) 15.19

$T_{LAG}=0.72\left({\frac {L\ast L_{ca}}{\sqrt {S}}}\right)^{0.38}$

(Foothills) 15.20

$T_{LAG}=0.38\left({\frac {L\ast L_{ca}}{\sqrt {S}}}\right)^{0.38}$

(Valleys) 15.21

where:

$T_{LAG}$ = lag time in hours.

$L$ = maximum flow length in miles.

$L_{ca}$ = length to the centroid in miles.

$S$ = weighted slope along the maximum flow path length in ft/mile.

The typical characteristics of watersheds for which the Riverside County equations were used include the following:

• Areas from 2 to 650 square miles.

Related Topics

• Computing Lag Time or Time of Concentration from Basin Data