Document: NUREG-0800
Document ID: b3542dd9-b995-4eba-aa6c-0f8f08f8c772
Document Type: srp
Title: FLOODS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340525.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.2
CFR Part: 
CFR Title: 

Content:
cations to evaluate hydrologic conditions used in determining the probable maximum flood for the site drainage system. Potential ponding on the site is also determined. The above reviews 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 CP reviews, the findings will consist of a statement indicating the completeness of the identification of site flood characteristics and flood design bases in compliance with 10 CFR Part 100 and GDC 2. For OL reviews, the flood history will be updated if necessary, with special attention to any new flood of record. Sample statements for CP reviews follow: The maximum flood known to have occurred on the A River was in 1796. The peak discharge at B City, Montana, was estimated to be 360,000 cubic feet per second (cfs). The applicant estimated that a compar- able flood would produce water surface elevation at the site of 116 feet MSL. The maximum flood during the period since records were maintained (1883) at B City was 350,000 cfs and occurred on October 3, 1929. These floods occurred prior to construction of several upstream dams. Flood flows are now regulated by C and D Reservoirs as well as by upstream hydropower plants. The applicant has estimated potential flooding from rainfall over the E River basin upstream from the site. The probable maximum flood (PMF), the upper level of flooding the staff considers to be reasonably possible, was estimated to produce a flow of 5,000,000 cfs near the city of F. This estimate was made by using 165% of the Corps of Engineers project design flood (PDF) estimate of 3,030,000 cfs at the same location, as modified by upstream flood control reservoirs. The 3,030,000 cfs project design flood flow is esti- imated to be partially diverted to the leveed G and H floodways upstream of the site, with 1,500,000 cfs continuing downstream within the levee system past the plant site. The applicant concluded that the