Document: NRC Regulatory Guide
Document ID: c7b1689b-ff17-4083-9fb1-f91b6965ea1a
Document Type: regulatory_guide
Title: Design Basis Floods for Nuclear Power Plants + HISTORY - HISTORY 02/2022 – DG-1290 , Proposed Revision 3 09/2014 – Periodic Review of Revision 2 – Revise 07/1980 – Errata to Revision 2 07/2024 – DG-1290 Revision 1 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740388.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.59
CFR Part: 
CFR Title: 

Content:
as follows: PMF Within Drainage Area Range, sq. mi. 50 to 500 100 to 1,000 500 to 5,000 1,000 to 10,000 5,000 to 50,000 10,000 or greater Adjusted to Index Drainage Area, sq. mil. 100 500 1,000 5,000 10,000 20,000 . The PMF values so adjusted were plotted on maps of the United States east of the 103rd meridian, one map for each of the six index drainage areas. It was found that there were areas on each map with insuf ficient points to define isolines. To fill in such gaps, conservative computations of approximate PMF peak discharge were made for each two-degree latitude-longitude intersection on each map. This was done by using enveloped relations between drainage area and PMF peak discharge (in cfs per inch of runoff), and applying appropriate probable max imum precipitation (PMP) at each two-degree latitude-longitude intersection. PMP values, obtained from References 3 and 4, were assumed to be for a 48 hour storm to which losses of 0.05 inch per hour were applied. These approximate PMF values were also plotted on the maps for each index drainage area and the enveloping isolines were drawn as shown on Figures B.2 through B.7. B.3.2.2 Use of Maps The maps may be used to determine PMF peak dis charge at a given site with a known drainage area as follows: 1. Locate the site on the 100-square-mile map, Figure B.2. 2. Read and record the 100-square-mile PMF peak discharge by straight-line interpolation between the isolines. 3. Repeat Steps 1 and 2 for 500, 1,000, 5,000, 10,000, and 20,000 square miles from Figures B.3 through B.7. 4. Plot the six PMF peak discharges so obtained on logarithmic paper against drainage area, as shown on Figure B.8. 5. Draw a smooth curve through the points. Reasonable extrapolations above and below the defined curve may be made. 6. Read the PMF peak discharge at the site from the curve at the appropriate drainage area. B.3.3 Probable Maximum Water Level When the PMF peak discharge has been obtained as outlined in the foregoing sections,