FLOOD02665

• County: Larimer
• County: Weld
• Community: Larimer and Weld Counties
• Stream Name: Cache La Poudre River Basin
• Basin: South Platte
• Title: Special Study Cache La Poudre River Basin Volume II - Hydrology
• Date: 10/1/1981
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

States, Atlas 2, Volume III, Colorado, published by the National Oce-

anic and Atmospheric Administration (NOAA) in 1973. In each case, a

50o-year value was estimated by extrapolating the selected Atlas values

on semilogarithmic paper. Adjustments for depth-area were based on the

depth-area relationship presented in the NOAA publication. Adjustments

for length of record were made on logarithmic-probability paper using

Beard's table of expected probability adjustments for various lengths

of record. The spatial variation of the rainfall potential shown in

the Atlas for the Cache la Poudre River basin was simulated in the

MITCAT model through the introduction of several hyetographs. The time

variation of the 6-hour rainfall for each hyetograph was based on a

study of hourly precipitation data recorded during major storms in the

South Platte River basin and refined to 30-minute values by using Civil

Works BuLetin 52-8, Plate No. 11 (1952) as a guide. The 6-hour

distribution is given in table 2 below.

.

Table 2
6-Hour Rainfall Distribution

End of Period
(minutes)

Percent of 6-Hour

30
60
90
120
150
180
210
240
270
300
330
360

2
4
4
5
9
10
40
10
6
4
4
2

LOSSES

The Soil Conservation Service (SCS) curve number technique was used

to model infiltration in the MITCAT model. A general soil map of Larimer

.

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