FLOOD10479

• County: Statewide
• Basin: Statewide
• Title: Precipitaion - Frequency Maps for Colorado
• Date: 10/1/1967
• Prepared For: Engineering Division, Coil Conservation Service
• Prepared By: Special Studies Branch, Office of Hydrology
• Floodplain - Doc Type: Floodplain Report/Masterplan

. 'to'

0.04

0.62

29

West of the Continental Divide Y3 = 0.270 + 0.002(X3) - 0.373(X5) 0.78
and North of the Crest of the
San Juan Hountains

0.14

0.98

35

0.88

0.121 -0.008(X3) + 0.690(X5)

East of the Continental Divide Y3 =
and South of the Crest of the
San Juan Hountains

50-percent probability 6-hour

0.24

2.38

66

0.326 + 0.011(X3) + 1.952(X5) 0.83

II/est of the Continental Divide Y2 =
and North of the Crest of the
San Juan Mountains

0.39

3.20

52

0.85

0.554 + 1.935(X5)

East of the Continental Divide Y2 =
~ and South of the Crest of the
San Juan Mountains

I-percent probability 24-hour

0.08

0.95

89

= 0.266 + 0.7l3(X2) + 0.024(Xl) 0.89
-0.001(X3) -0.049(X4)
-0.001(2)

West of the Continental Divide Yl
and North of the Crest of the
San Juan Mountains

0.21

1.38

78

0.83

1.305 + 0.133(Xl) - 0.013(2)

East of the Continental Divide Yl =
and South of the Crest of the
San Juan Mountains

50-percent probability 24-hour

Standard
Error of
Estimate

Nean of the
Obs. Values

No. of
Stations

Corr.
Coeff.

Equation

Region of Applicability

Table 5. Relations for estimating the rainfall-frequency values for the Hay to October season at the 50-
and I-percent probability levels in regions of sparse or no data.

Yl is the 2-year 6-hour precipitation amount in inches.
Y2 is the 100-year 6-hour precipitation amount in inches.
Xl is the 2-year 24-hour precipitation amount in inches.
X2 is the 100-year 24-hour precipitation amount in inches.
X3 is the 2-year 6-hour precipitation amount in inches.
2 is the elevation in hundreds of feet.

List of Variables

(Region of applicability - Basins primarily located in Colorado, Utah and Nevada (includes
those portions within Colorado of basins on the eastern slopes of the Rockies even though
the major part of the basin is outside Colorado.)

0.47

2.34

144

0.91

Y2 = - 0.517 + 0.470(X2) + 1.370(X3)

(Region of applicability - San Juan, Rio Grande and extreme southern Colorado east of
Rio Grande Basin.)

~

0.50

3.16

10:3

0.91

Log(Y2) · 0.079 + 0.888(Log(X2)) - 0.003(2)

100-YEAR RETURN PERIOD

(Region of applicability - All basins primarily in the states of Arizona, New Mexico, Colorado,
Utah and Nevada (includes those portions of basins on the eastern slopes of the Rockies within
New Mexico and Colorado even if the major part of the basin is outside the state).)

0.16

1.10

26:2

0.92

Yl · 0.902 + 1.15l(Log(Xl)) - 0.003(Z)

2-YEAR RETURN PERIffi>

Standard
Error of
Estimate

Mean of the
Obs. Values

No. of
Stat:lons

Corr.
Coeff.

Equation

Table 4. Relations for estimating the 2- and 100-year 6-hour plrecipitation amounts in regions of
sparse or no data.