Document: NUREG-0800
Document ID: 904b56ce-40c5-4058-b0ad-837d98f63c2a
Document Type: srp
Title: PROBABLE MAXIMUM FLOOD (PMF) ON STREAMS AND RIVERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070730405.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.3
CFR Part: 
CFR Title: 

Content:
requirements identified in Subsection II. 1. Design Bases for Flooding in Streams and Rivers. The drainage area that contributes runoff to the location on the stream network adjacent to the plant site should be evaluated by delineating ridge lines on a topographic map. More recently, automated drainage network and contributing area delineation procedures have also become available that use digital elevation and digitized stream network data from the United States Geological Survey. The staff reviews the applicant’s flood estimates using currently available methods. If a significant discrepancy exists in drainage areas between the two estimates, the staff will need the applicant to provide more data to support its estimate, or to accept the staff’s estimate and re-analyze flooding of the streams and rivers. Probable maximum precipitation on the drainage area estimated above determines in the probable maximum flood adjacent to the plant site. The PMP is estimated for the drainage area using currently applicable National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) hydrometeorological reports (HMR). The rainfall-runoff response characterized by rainfall losses and overland flow mechanisms in the drainage area results in flooding that propagates downstream via the stream network. The staff may consult the U.S. Army Corps of Engineers (USACE) and other appropriate State and Federal agencies to determine the appropriate rainfall-runoff response functions and other watershed parameters. In its review of the PMF on streams and rivers, the staff may verify the applicant’s estimate, perform its own independent analysis, or accept an estimate from a Federal or State agency that has the authority and responsibility to carry out these estimates. In its independent analysis, the staff should use currently accepted runoff generation and flood routing methods, such as those made available by the USACE, and hydraulic characteristics such as