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Design Rainfall Distributions Based on NOAA Atlas 14.

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Presentation on theme: "Design Rainfall Distributions Based on NOAA Atlas 14."— Presentation transcript:

1 Design Rainfall Distributions Based on NOAA Atlas 14

2 WinTR-20 NOAA 14 Data March General Considerations Standard NRCS rainfall distributions were developed between 1960 and NRCS is adopting NOAA Atlas 14 in the states where it is applicable. Will a new set of rainfall distributions be required ? If so, how to develop and apply them ?

3 WinTR-20 NOAA 14 Data March Standard Rainfall Distributions

4 WinTR-20 NOAA 14 Data March Geographic Application

5 WinTR-20 NOAA 14 Data March Steps in developing a distribution Determine ratios of x hour / 24 hour rainfall. Place the rainfall ratio for the shortest duration in the center of the distribution. Symmetrically place each larger duration to include the shorter durations.

6 WinTR-20 NOAA 14 Data March Example of a Nested Distribution 3 hr hr 0.7

7 WinTR-20 NOAA 14 Data March NOAA Atlas 14 web site Download rainfall frequency data at:

8 WinTR-20 NOAA 14 Data March Select State

9 WinTR-20 NOAA 14 Data March Selected Ohio

10 WinTR-20 NOAA 14 Data March Selected Columbus Ohio

11 WinTR-20 NOAA 14 Data March NOAA 14 Rainfall Ratios

12 WinTR-20 NOAA 14 Data March Symmetrical Distribution

13 WinTR-20 NOAA 14 Data March Compare to Type II

14 WinTR-20 NOAA 14 Data March Where Type II and Type III compare with NOAA- derived distribution, 25-yr rainfall Purple: Type II Pink: Type III Green: both

15 WinTR-20 NOAA 14 Data March Points used to represent Maryland Counties

16 WinTR-20 NOAA 14 Data March

17 WinTR-20 NOAA 14 Data March

18 WinTR-20 NOAA 14 Data March Future Directions Develop software to easily use the data. Use GIS data layers to derive site-specific rainfall data for hydrologic modeling.

19 WinTR-20 NOAA 14 Data March


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