FLOOD02408

• County: Statewide
• Community: Nationwide
• Basin: Statewide
• Title: Design Hydrographs for Very Small Wathersheds from Rainfall
• Date: 7/1/1962
• Prepared By: USDA Hydrograph Laboratory, Civil Engineering Section Colorado State University
• Floodplain - Doc Type: Educational/Technical/Reference Information

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FIGURES

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Mathematical model of flood hydrograph

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m

m
G

m
G

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G [Q]m
Functional relationship between a = e mJ

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(1 + ;;,) and

r

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Typical hyetographs with superposition of statistical rainfall parameters for: mean
time, S1 ; standard deviation, 82 ; and skewness, 83 . .. .......

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Illustrative case of situation in which the peak rate of runoff (q )
was reduced below the observed peak. , . . . . . . . . . . . . o.

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for the fitted model

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Typical examples of arbitrary classification of goodness of fit

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Typical attempt to fit model to observed hydrograph

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Shifting of mathematical model in time to obtain better overall fit

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Typical difference between biased and unbiased coefficients of determination for a
sample size of 47 , . , , . , . . . . , . . . . . . . . . . . . . .. .....

Typical variation of the unbiased coefficient of determination, Il2
variables are included in the regression . . . . . , . . . . .

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as more

Variation of the residual of W with actual peak discharge, qo . . . . .

Variation of the residual of qo with actual peak discharge. qo ......

Variation of the residual of G with actual peak discharge, qo

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Closeness with which estimated hydrographs, predicted from regression equations,
can approximate the observed hydrograph and the best-fitting model . . . . . . . .

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Difference between estimated hydrograph obtained from regressions and observed
or best-fitting hydrographs, when the peak rate has been poorly predicted. . . . .

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Difference between estimated hydrograph obtained from regressions and observed
or best-fitting hydrographs, when the peak rate and the volume have been poorly
predicted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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16 Time of concentration, T c or T 9 J for headwater areas based upon dimensions

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from outlet to ridge . .

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Nomograph for predicting total runoff volume,

Winches. . .

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Nomograph for predicting peak runoff rate, q inches/hour...
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Estimated hydrograph computed from watershed and storm parameters,
to one actually observed. . . . . . . . . . . . . . . . . . . . . . . . . .

compared

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