FLOOD07698

• County: Statewide
• Community: Rock Rapids, Iowa
• Basin: Statewide
• Title: Problem Identification Report Rock River at Rock Rapids Reconnaissance Study Section 205
• Date: 4/1/1995
• Prepared For: US Army Corps of Engineers
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Project

I
I I

I
I
I

Although there were only slight discrepancies between the discharges

calculated for this study and those presented in the FIS, the Omaha

District decided to use the peak flows calculated from the 1993 Iowa

regression equations due to ambiguous methodology described in the FIS

report. The SOO-year peak discharges were extrapolated on log probability

paper from the 2-, 5-, 10-. 25-, SO-, and 100-year discharges which were

calculated using the 1993 Iowa regression equations. Table 2 shows the

peak discharge values used in the hydraulic model for this study.

Figure 2 presents discharge-frequency curves for the information in

table 2.

I
I

I
I

Table 2
Existing Conditions Peak Discharges
Used in Hydraulic Model
Rock River at Rock Rapids, Iowa

I
I

FLOODING SOURCE
AND LOCATION

lO-YR

PEAK DISCHARGE Ic.f.s.)
SO-YR 100-YR SOO-YR

Rock River just upstream
from Tom Creek
Rock River just downstream
from Tom Creek

16,230

29,200

35,S60

S7,OOO

17 ,160

30,780

37,440

60,000

I
I

I
I

I
I
I

18

I