FLOOD03276

• County: Statewide
• Basin: Statewide
• Title: Hydrologic Engineering Methods for Water Resources Development Volume 4
• Date: 10/1/1973
• Prepared For: US
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

M - .09 + (.029 + .0084kW + .007R)(T-TF)

(3-1)

The modified equation for metric units is:

M - 2.286 + (1.326 + .2l34kW + .125R)(T-TF)

where:

M - Snowmelt in inches (or mm)

k a convection-condensation melt constant for a basin which

represents the mean exposure of the basin; k would range

from 1.0 for an unforested basin to 0.3 for a densely

forested basin

W a Wind speed in miles per hour (or kph) at 50 feet (15m) above
the snow

R a Rainfall in inches (or mm) per day

T - Air temperature in degrees F (or degrees C) at the 10-foot

level (assumed to equal the temperature of rainwater)

TF - Temperature of the snowpack in degrees F (or degrees C),

usually assumed to be 320F (OOC) for a melting snowpack

Equation 3-1 can be further modified by adding a dimensionless coefficient

to account for undetermined variation in basin snowmelt. This modification

results in the following equation:

MaC (.09 + (.029 + .0084kW + .007R) (T-TF))

or MaC (2.286 + (1.326 +.2l34kW + .125R)(T-TF))

(3-2)

for English and metric units, respectively.

When rainfall is not occurring, snowmelt can be computed for a partly-

forested basin by the following equation with English units:

M - k'(l-F) (.004S) (I-A) + k(.0084W)(.22T' + .78TD') + F(.029T') (3-3)

When metric units are used, equation 3-3 becomes:
M - k'(l-F) (.1015S) (I-A) + k(.2134W) (.22T' + .78TD') + F(1.326T')

where:

k' - Basin shortwave radiation melt factor, indicative of average

3-06