Flood Event Combinations

DOE-STD-1023-95

The causes of dam failure to be evaluated include: hydrologic, seismic, hydrostatic, operation error,

random structural failure, upstream dams, and landslides (McCann and Boissonnade, 1988b).

Dam failure-induced flood levels shall be determined by analyses using validated dam break models

(Fread, 1984). Uncertainty for the dam break model analysis parameters (e.g., breach size, time to

failure, flood time arrival) shall be accounted for in the analysis (McCann and Boissonnade, 1988b).

Simplified dam failure analysis is acceptable (McCann, et al., 1985) if the analysis accounts for

uncertainty.

3.3.4 Flood Event Combinations

For each primary potential flood source, the DBFL shall consider several event combination cases as

specified below:

(1) River Flooding:

Case 1: Peak flood elevation due to all flooding contributors with the

exception of upstream dam failure.

Case 2: Wind-waves corresponding to winds acting in the most favorable

direction and Case 1. The wind should be determined from a probabilistic

analysis that considers the joint occurrence of river flooding and wind

generated waves and as a minimum corresponds to the 2-year wind.

Case 3: Ice or debris forces (static and dynamic) and Case 1.

Case 4: Peak and ground water level and Case 1.

(2) Levee/Dam Failure:

Case 1: Peak flood elevation due to all modes of failure (i.e.,

overtopping, seismically or landslide induced, random structural failure,

upstream dam failure, debris or ice dam failure, etc.)

Case 2: Wind-waves corresponding to winds acting in the most

favorable direction and Case 1. The wind should be determined from a

probabilistic analysis that considers the joint occurrence of dam failure

and wind generated waves and as a minimum correspond to the 2-year

wind.

(3) Storm Surge/Seiche:

Case 1: Peak flood levels plus mean high tide levels.

Case 2: Surge-associated waves and Case 1.

(4) Tsunami:

Tsunami-tide effects corresponding to the mean high tide level.