Document: NUREG-0800
Document ID: 3e2b0f8e-404f-49b4-8dde-3452e69e6218
Document Type: srp
Title: PROBABLE MAXIMUM FLOOD (PMF) ON STREAMS AND RIVERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070241.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.3
CFR Part: 
CFR Title: 

Content:
trolling; the design basis flood protection level is established by another flood phenomenon (e.g., the probable maximum hurricane). 3. The site is "dry"; that is, the site is well above the elevation attained by a PMF (with coincident wind waves). When condition 1 is applicable, the staff will assess the flood level (described in subsection III). The assessment may be made independently from basic data, by detailed review and checking of the applicant's analyses, or by comparison with estimates made by others that have been reviewed in detail. The applicant's estimates of the PMF level and the coincident wave action are acceptable if the estimates are no more than 5% less conservative than the staff's estimates. 2.4.3-3 DRAFT Rev. 4 - April 1996 If the applicant's estimates of discharge are more than 5% less conservative than the staff's, the applicant should fully document and justify its estimates or accept the staff's estimates and redesign applicable flood protection. When conditions 2 or 3 apply, the staff analyses may be less rigorous (described in subsection III). For condition 2, acceptance is based on the protection level estimated for another flood-producing phenomenon exceeding the staff estimate of PMF water levels. For condition 3, the site grade must be well above the staff assessment of PMF water levels. The evaluation of the adequacy of the margin (difference in flood and site elevations) is generally a matter of engineering judgment. The judgment is based on the confidence in the flood level estimate and the degree of conservatism in each parameter used in the estimate. Appropriate sections of the following documents are used by the staff to determine the acceptability of the applicant's data and analyses. Regulatory Guide 1.59 provides guidance for estimating the PMF design basis. Regulatory Guide 1.29 identifies the safety-related structures, systems, and components, and Regulatory Guide 1.102 describes acceptable flood protection to prevent the