FLOOD04543

• County: Statewide
• Community: Harrison County, Iowa
• Basin: Statewide
• Title: California Bend Missouri River Fish and Wildlife Mitigation
• Date: 11/1/1994
• Prepared For: US Army Corps of Engineers
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Data ‎(general)‎

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stream site that falls within each precipitation polygon shown in figure 5 is calculated, and a
weighted average for the basin is computed as

7TF= (A,)(7TF,) + (A.)(T7'Fol +.. . + <A.J (T71',>.

(19)

where TrF is the weighted average for 2-year, 24-hour precipitation intensity, in inches;

Ai is the approximate percentage of the total drainage area of a basin within the ith 2-year,
24-hour precipitation intensity polygon shown in figure 5 (i = 1, . . . , p);

TrFj is the 2-year, 24-hour precipitation intensity, in inches, for the ith polygon shown in figure
5 (i = 1, . . . , p); and

P is the total number of 2-year, 24-hour precipitation intensity polygons shown in figure 5
everlain by the drainage-divide boundary of a basin.

For example, if approximately 70 percent of the total drainage area for a stream site overlies the
polygon labeled as 3.15 in. and approximately 30 percent of the total drainage area overlies the
polygon labeled 3.05 in., then the weighted average for the basin is calculated as

7TF= (A,) (T7'F,) + (A.) (T71'.I.
= (0.70) (3.15) + (0.30) (3.05~
=3.12 in.

61 ESTIMATING DESIGN-FLOOD DISCHARGES FOR STREAMS IN IOWA