Document: NUREG-0800
Document ID: aee3277d-bcab-4cf4-bdb2-fb607503b041
Document Type: srp
Title: PROBABLE MAXIMUM FLOOD (PMF) ON STREAMS AND RIVERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340529.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.3
CFR Part: 
CFR Title: 

Content:
s in the region to develop "regional drainage area vs. PMF discharge (cubic feet per second/square mile)" data, for extrapolation to the site. 2. Envelop the above data points to obtain an estimate of the PMF applicable to the site. 2.4.3-3 Rev. 3 - April 1989 3. Increase the estimate based on a judgment as to the applicability of the basic estimates. An increase in the range of 10% to 50% is generally appropriate. 4. If warranted by relative elevation differences between the site and adjacent stream, estimate the flood level at the site using slope-area techniques or water surface profile computations. 5. Estimate wind (2-yr extreme windspeed) wave runup based on breaking or 1% wave heights. Criteria for estimating windspeed are discussed in ANSI N170 and References 16, 18, and 19. 6. Compare resultant water level with proposed plant grade and lowest safety- related facility that can be affected. The above items of review are performed only when applicable to the site or site region. Some items of review may be done on a generic basis. IV. EVALUATION FINDINGS For construction permit (CP) reviews, the findings will summarize the applicant's and staff's estimates of the peak PMF runoff rate and water level (including allowance for coincident wind-generated wave activity) at the site. If the applicant's estimates are within the criteria (described in subsection II), staff concurrence will be stated. If the staff's estimates are 5% more conservative than the applicant's estimates, if the flood conditions may adversely affect the proposed plant, and if the applicant has been unable to support his estimates, a statement requiring use of the staff bases will be made. If the flood conditions do not constitute a design basis, the findings will so indicate. For operating license (OL) reviews that have received detailed PMF reviews during the CP review, the CP conclusions will be referenced. Any flood potential not identified during the CP review will be noted. If.Regulatory