C. For rivers which could be potential sources of site flooding, the potential for flooding shall be characterized
by collecting the following information:
Location and elevation of the rivers at the location closest to the site,
Historical records of stream flow data (maximum yearly peak discharge and stage elevation) with
recording location, Probable maximum flood level, that may be expected from a combination of the most
critical meteorological and hydrologic conditions,
Characterization of the geometric and hydraulic properties of the channel closest to the site. The
geometric properties of the channel include Manning's roughness coefficient and top-width elevation tables
for cross sections, and streambed slope.
For sites with poor or inadequate historical data, results of paleoflood analyses should be provided for
sites containing facilities with SSCs in Performance Category 4 if there is a potential of flood at the site.
Presence of bridges or natural river flow constrictions which could cause flooding due to ice or debris
D. For rivers for which no peak discharge records are available, the following information shall be gathered:
Characteristics of the watershed basins of the river,
Properties of the drainage basins including topographic maps of the basin and land cover maps.
5.3.4 Dam, Levee, or Dike Failure
A. Historic experiences and analytical studies indicate that floods associated with a dam break can significantly
exceed flood levels that occur due to natural events. All dams upstream on rivers in the regional area of the
site shall be identified and their characteristics summarized. These characteristics include: dam name, owner
of dam, type of dam (e.g., earth fill, concrete, etc.,), year of completion, river name and location (e.g., river
mile), total height, capacity, and closest distance from the river to the site.
B. For dams that could pose a threat to the site should they fail, a detailed collection of data shall be conducted.
Failures of dams that could pose a hydrologic hazard to the site include dams close enough to the site with
relatively large storage capacity or distant dams with large storage capacity. The collection of data includes
collecting existing dam break studies or data necessary to perform dam break analyses.
C. For dams for which dam break studies have been conducted as part of dam safety emergency
management planning evaluations, results of these studies shall be collected, including date of study, dam
failure scenario (e.g., flood, earthquake, static failure due to internal erosion), peak discharge and elevation
at closest point from site.
D. For dams for which no dam break studies are available or for which dam break studies are unavailable for
all the potential hazards (seismic, flood, landslide, upstream dam failure), data shall be collected to conduct
E. The data to be collected include data necessary to perform a river flooding hazard analysis of the river reach
upstream of the dam and/or upstream dams, seismic hazard analysis, potential landslide hazard analysis of
the embankment or the dam itself, and dam break analysis. These data include:
Results of seismic hazard analysis (Section 5.4),