Document: NUREG-0800
Document ID: 9ec109d9-dfac-443f-a128-99771d0f5c88
Document Type: srp
Title: FLOODS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0701/ML070100647.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.2
CFR Part: 
CFR Title: 

Content:
ff discharge estimates presented in standard texts, are used to estimate discharge on the site drainage system under local intense precipitation. Where generalized runoff models are used, coefficients used for the site and region are compared to information available at documented locations to evaluate hydrological conditions used in determining the probable maximum flood for the site drainage system. Protection from flooding caused by local intense precipitation cannot be mitigated by siting changes. Flooding from local intense precipitation should be mitigated by an effective and efficient site drainage system. The staff reviews site drainage design and any appropriate flooding protection required for safety-related SSC in this section of the SER. Flooding protection requirements are described in detail in SER Section 2.4.10. 2. Stream Flooding: The staff reviews the complete history of flooding in rivers and streams near the site. The staff’s review uses historical records of streamflow (from the United States Geological Survey (USGS) or the U.S. Army Corps of Engineers (USACE)) and accompanying hydrometeorological conditions to evaluate flood- generation mechanisms that are relevant for the site safety review. In order to establish the design-basis flood water elevation, the staff evaluates several severe flooding scenarios, which may include: (a) PMF coincident with upstream dam- failure (single or multiple failures including cascading failures due to hydrological causes) and wind-induced waves, (b) flooding due to backwater effects of downstream ice jams or collapse of an upstream ice dam, both independently and coincident with a winter probable maximum flood, and (c) a combination of less severe floods in streams combined with flooding effects of surges, seiches, and tsunamis, when applicable at a 2.4.2-10 Revision 4 - March 2007 site. Individual flood-causing mechanisms are reviewed in SER Sections 2.4.3 through