1. Midwest Regional Flood Frequency Analysis
CPT Ben Bigelow
Dr. David Maidment
Dr. Edward Holley
University of Texas at Austin

2. Project Objectives Develop a GIS-based Map product as a base map
Determine a relationship between discharge and drainage area
Test on Des Moines River Basin
Develop design hydrographs
Assess routing methodology for Des Moines and Mississippi
University of Texas at Austin

3. Midwest Flood Discharge -Duration- Frequency
University of Texas at Austin

4. Test Area Part of the Upper Mississippi Basin 11 gages
Des Moines - 5
Raccoon - 1
Iowa-1
Focused test on Des Moines River
University of Texas at Austin

5. Data Development 500 m DEM Delineated drainage areas for each gage
Used CRWR-PREPRO to develop data
Results in an HMS basin file for the Des Moines Basin and for the total test area
University of Texas at Austin

6. Des Moines River 5 gaging stations
Smoothed frequency curves available for all gages
Van Meter Gage on Raccoon River
Total drainage area is sq miles
University of Texas at Austin

7. Des Moines DDF Curves
University of Texas at Austin

8. Regional Flood Frequency
Four Variables: Duration (D), Area (A), Frequency & Volume
Mean discharge, Q = Volume/Duration
Q(A, D) = Q(A, 3)*[Q(D)/Q(3)] where
Q(A, D) is the design mean discharge from area A for the maximum D day period in the flood
Q(A, 3) is the discharge-area function for the maximum 3-day period in the flood
Q(D)/Q(3) is the discharge-duration ratio
University of Texas at Austin

9. Area Function Comparison
Mississippi
River Basin
Des Moines
River Basin
Y: Daily Average flow for maximum 3-day volume X: Drainage Area
Regression used to find best fit function
Mississippi and Des Moines clearly trend differently
Inadequate data to determine trend from square mile drainage area
University of Texas at Austin

10. Duration Function Comparison
Mississippi
River
Des Moines
River
Y: Average [ Q(D)/ Q (3)] where D = 1,3,10,15 & 30 days
X: Duration
Spread of the data points are the observed values at gages
University of Texas at Austin

11. Flow Determination (cont)
Use analytical functions to estimate the discharge for other durations and compare to values from frequency analysis at individual gages
Q(A,D) = Q(A, 3)*[Q(D)/Q(3)]
The analytical functions were tested for both the large (Mississippi) basin (4 gages) and the small (Des Moines) basin (6 gages).
University of Texas at Austin

12. Des Moines Discharge Comparisons
Actual Values: Blue points
Analytical Function: Red Line
University of Texas at Austin

13. Mississippi Discharge Comparisons
University of Texas at Austin

14. Design Discharge Profile, Des Moines River
1-day, 100-year peak flow
Raccoon River
University of Texas at Austin

15. Design Discharge Profile, Mississippi River
Iowa-Cedar
Rock
Des Moines
1-day, 100-yr peak flow
Des Moines
Iowa-Cedar
Rock
University of Texas at Austin

16. Conclusions
Discharge,Q is a function of duration, D, area, A, and frequency
choose a frequency (100 years)
choose a reference duration (3 days)
Q(A, D) = Q(A, 3) * [Q(D)/Q(3)]
tests on Des Moines basin (6 gages) and Upper Mississippi (4 gages)
University of Texas at Austin

17. Conclusions Within a river basin (Des Moines or Upper Mississippi)
discharge-area function is nearly linear
discharge-duration ratio is consistent among all gages
These functions are scale dependent and different for Mississippi as compared to Des Moines
University of Texas at Austin

18. Conclusions
Flow profiling tool allows continuous plot of design discharge along the river
University of Texas at Austin