Kan. Admin. Regs. § 5-40-31 - Design duration rainfall depth

(a) If the time of concentration is six hours or less, a duration of six hours shall be used for all design storms. The appropriate six-hour storm depth, in inches, shall be selected from the following table.

County Probability of occurrence in any year

50% 20% 4% 2% 1% PMP

Allen 2.7 3.5 4.8 5.4 6.1 28.0

Anderson 2.7 3.5 4.8 5.3 6.0 27.8

Atchison 2.6 3.4 4.5 5.1 5.7 27.2

Barber 2.4 3.2 4.4 5.0 5.7 27.3

Barton 2.3 3.0 4.1 4.8 5.3 26.6

Bourbon 2.7 3.5 4.8 5.4 6.0 28.1

Brown 2.5 3.2 4.4 5.0 5.6 27.0

Butler 2.6 3.4 4.7 5.3 6.0 27.7

Chase 2.6 3.4 4.6 5.2 5.9 27.5

Chautauqua 2.7 3.5 4.9 5.5 6.2 28.3

Cherokee 2.8 3.6 5.0 5.5 6.2 28.5

Cheyenne 1.8 2.4 3.4 3.8 4.3 24.7

Clark 2.2 3.0 4.1 4.7 5.3 26.7

Clay 2.5 3.2 4.3 5.0 5.5 26.8

Cloud 2.4 3.1 4.2 4.8 5.4 26.6

Coffey 2.7 3.5 4.7 5.3 6.0 27.8

Comanche 2.3 3.1 4.2 4.9 5.5 27.0

Cowley 2.6 3.4 4.8 5.4 6.1 28.0

Crawford 2.8 3.6 4.9 5.4 6.1 28.3

Decatur 1.9 2.6 3.6 4.2 4.6 25.3

Dickinson 2.5 3.2 4.4 5.1 5.6 27.1

Doniphan 2.5 3.2 4.5 5.0 5.6 27.0

Douglas 2.6 3.4 4.6 5.2 5.8 27.5

Edwards 2.2 2.9 4.1 4.7 5.3 26.7

Elk 2.7 3.5 4.8 5.4 6.1 28.1

Ellis 2.1 2.9 3.9 4.6 5.0 26.2

Ellsworth 2.3 3.1 4.2 4.9 5.4 26.7

Finney 2.0 2.6 3.8 4.3 4.8 26.8

Ford 2.1 2.8 4.0 4.6 5.1 26.4

Franklin 2.7 3.5 4.7 5.2 5.9 25.8

Geary 2.5 3.2 4.4 5.1 5.7 27.1

Gove 2.0 2.6 3.7 4.3 4.7 25.7

Graham 2.0 2.7 3.8 4.4 4.8 25.8

Grant 1.9 2.6 3.7 4.2 4.7 25.6

Gray 2.0 2.7 3.9 4.4 4.9 26.1

Greeley 1.8 2.5 3.4 3.9 4.4 25.0

Greenwood 2.7 3.5 4.8 5.3 6.1 27.8

Hamilton 1.8 2.5 3.5 4.0 4.5 25.2

Harper 2.5 3.3 4.5 5.2 5.9 27.5

Harvey 2.5 3.3 4.5 5.1 5.8 27.4

Haskell 2.0 2.7 3.8 4.3 4.8 25.9

Hodgeman 2.1 2.8 3.9 4.5 5.0 26.3

Jackson 2.6 3.4 4.5 5.1 5.7 27.2

Jefferson 2.6 3.4 4.6 5.1 5.8 27.3

Jewell 2.3 2.9 4.0 4.7 5.1 26.3

Johnson 2.6 3.4 4.6 5.2 5.8 27.5

Kearny 1.9 2.6 3.6 4.1 4.6 25.5

Kingman 2.4 3.2 4.4 5.1 5.7 27.3

Kiowa 2.2 2.9 4.2 4.8 5.4 26.7

Labette 2.8 3.6 5.0 5.5 6.2 28.4

Lane 2.0 2.7 3.7 4.3 4.8 25.8

Leavenworth 2.6 3.4 4.6 5.1 5.8 27.4

Lincoln 2.3 3.0 4.2 4.8 5.3 26.6

Linn 2.7 3.5 4.8 5.3 6.0 27.9

Logan 1.9 2.5 3.6 4.1 4.6 25.3

Lyon 2.6 3.4 4.6 5.2 6.0 27.5

Marion 2.5 3.3 4.5 5.2 5.8 27.3

Marshall 2.5 3.2 4.3 4.9 5.5 26.8

McPherson 2.5 3.2 4.4 5.1 5.7 27.1

Meade 2.1 2.8 4.0 4.6 5.1 26.3

Miami 2.7 3.5 4.7 5.2 5.9 27.7

Mitchell 2.3 3.0 4.1 4.7 5.2 26.4

Montgomery 2.8 3.5 5.0 5.5 6.2 28.3

Morris 2.6 3.4 4.5 5.1 5.8 27.3

Morton 1.9 2.5 3.6 4.1 4.6 25.4

Nemaha 2.5 3.2 4.4 5.0 5.6 26.9

Neosho 2.7 3.5 4.9 5.5 6.1 28.2

Ness 2.1 2.8 3.9 4.5 4.9 26.1

Norton 2.0 2.6 3.7 4.3 4.7 25.6

Osage 2.6 3.4 4.6 5.2 5.9 27.5

Osborne 2.2 2.9 4.0 4.6 5.1 26.2

Ottawa 2.4 3.1 4.3 4.9 5.4 26.8

Pawnee 2.2 2.9 4.1 4.7 5.2 26.6

Phillips 2.1 2.8 3.8 4.4 4.9 25.8

Pottawatomie 2.5 3.2 4.4 5.0 5.6 27.0

Pratt 2.3 3.1 4.3 4.9 5.5 27.0

Rawlins 1.9 2.5 3.5 4.0 4.5 25.0

Reno 2.4 3.2 4.4 5.0 5.7 27.2

Republic 2.3 3.0 4.1 4.8 5.3 26.4

Rice 2.4 3.1 4.3 4.9 5.5 26.9

Riley 2.5 3.2 4.4 5.0 5.6 27.0

Rooks 2.1 2.8 3.9 4.5 4.9 26.0

Rush 2.2 2.9 4.0 4.6 5.1 26.4

Russell 2.2 2.9 4.1 4.7 5.2 26.5

Saline 2.4 3.1 4.3 5.0 5.5 26.9

Scott 1.9 2.6 3.6 4.2 4.7 25.5

Sedgwick 2.5 3.3 4.6 5.2 5.9 27.5

Seward 2.0 2.7 3.8 4.4 4.9 26.0

Shawnee 2.6 3.4 4.6 5.1 5.8 27.4

Sheridan 2.0 2.6 3.7 4.2 4.7 25.5

Sherman 1.8 2.4 3.4 3.9 4.4 24.8

Smith 2.2 2.9 3.9 4.6 5.0 26.1

Stafford 2.3 3.0 4.2 4.9 5.4 26.9

Stanton 1.9 2.5 3.6 4.1 4.5 25.3

Stevens 1.9 2.6 3.7 4.3 4.7 25.8

Sumner 2.6 3.4 4.7 5.3 6.0 27.8

Thomas 1.9 2.5 3.5 4.1 4.5 25.2

Trego 2.0 2.7 3.8 4.4 4.9 25.9

Wabaunsee 2.6 3.4 4.5 5.1 5.8 27.3

Wallace 1.8 2.4 3.4 3.9 4.4 24.9

Washington 2.4 3.1 4.2 4.9 5.4 26.6

Wichita 1.9 2.5 3.5 4.1 4.5 25.3

Wilson 2.7 3.5 4.9 5.4 6.1 28.1

Woodson 2.7 3.5 4.8 5.4 6.1 28.0

Wyandotte 2.6 3.4 4.6 5.1 5.8 27.4

(b) If the time of concentration of the watershed, or any subwatershed being used to develop the inflow hydrograph, is more than six hours, the ratio for the time equal to or greater than the computed time of concentration shall be selected from the following table. Linear interpolation shall be acceptable. That ratio shall be multiplied by the depth of the six-hour rainfall in the table in subsection (a). The resulting depth is the design duration rainfall depth.

Relative increase in rainfall amount for storm durations over six hours

Time (hours) 100-year ratio PMP ratio

6 1.000 1.000

6.5 1.019 1.013

7 1.035 1.025

7.5 1.051 1.037

8 1.066 1.048

8.5 1.081 1.058

9 1.094 1.068

9.5 1.108 1.078

10 1.120 1.087

10.5 1.132 1.096

11 1.144 1.104

11.5 1.155 1.112

12 1.166 1.120

13 1.187 1.134

14 1.207 1.148

15 1.225 1.161

16 1.243 1.173

17 1.259 1.185

18 1.275 1.196

20 1.305 1.217

22 1.333 1.236

24 1.359 1.254

(c) If the drainage area exceeds 10 square miles, the rainfall depth obtained from the table in subsection (a) may be reduced by the ratio shown in the table in this subsection. The ratio for the zone in which the dam is located and a drainage area less than or equal to the actual drainage area above the dam shall be selected. The use of linear interpolation shall be acceptable. That ratio shall be multiplied by the depth of rainfall from the table in subsection (a). The result is the design duration rainfall depth. The ratios in subsection (b) and this subsection may be used together, if subsections (b) and (c) both apply.

Drainage Reduction ratio

area

(sq. mi.) Zone 1 Zone 2 Zone 3

10 1.00 1.00 1.00

12 0.99 0.99 0.98

15 0.97 0.95 0.93

17 0.96 0.94 0.91

20 0.94 0.91 0.88

22 0.93 0.90 0.86

25 0.92 0.88 0.83

27 0.92 0.87 0.82

30 0.91 0.86 0.80

35 0.90 0.84 0.77

40 0.88 0.82 0.75

45 0.87 0.80 0.72

50 0.86 0.78 0.70

60 0.84 0.75 0.65

70 0.82 0.72 0.62

80 0.80 0.70 0.59

90 0.79 0.68 0.57

100 0.78 0.67 0.55

Zone 1, zone 2, and zone 3 shall have the meanings specified in K.A.R. 5-40-1 under the definition of a "stream."

Notes

Kan. Admin. Regs. § 5-40-31

Authorized by and implementing K.S.A. 2006 Supp. 82a-303a; effective May 18, 2007.