WSP09960

• File Number: 8407.600
• Description: Platte River Basin - River Basin General Publications - Kansas General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/1/1971
• Author: Kansas Water Resourc
• Title: Kansas Streamflow Characteristics - Part 8 - In-Channel Hydraulic Geometry of Streams in Kansas - Technical Report Number 8
• Water Supply Pro - Doc Type: Report/Study

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Variation of Parameters in Downstream Direction

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The same frequency of discharge should be used at all locations
when studying changes in hydraul ic-geometry parameters of river
channels in a downstream direction. The discharge for 10-percent
duration was selected as the dominant discharge to give a full
channe 1 but st ill be wi th i n banks (Henderson, 1961).

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Figure 7 shows the change in parameters in a downstream direction
with 10-percent duration of discharge for stations included in this
study on the Republ ican, Smoky Hill, and Kansas rivers. The mean
I ines through the points were fitted by eye. Some of the scatter
about the relation lines on the width and depth graphs may be due
to the location of the stations at a section not representative of
the average cross section. The exponents are nearly the same as the
average values found by Leopold and Maddock in their river basin
study.

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According to Leopold and Maddock (1953, p. 14), "The general
al inement of points on the downstream graph indicates that in a
given river basin where all cross sections are experiencing the
same frequency of discharge, the corresponding values of depth,
width, and velocity at different cross sections having the same
discharge tend to be similar, regardless of where in the watershed
the cross sections may be."

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STATEWIDE GENERALIZATION

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The data for all stations were analyzed by least-squares regressions
of their logarithms. The regression equation is in the form:

y ~ aQz

(5)

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where Y is a dependent variable (width, depth, or velocity), a is the
regression constant, z is the regression coefficient, and Q is the
discharge for a specified discharge duration or the average discharge.

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Hydraul ic equations for each parameter were computed for each
discharge duration selected and are shown graphically on figures
8-11. The equation for the relation line is shown on each figure.
Rather than showing the standard error of estimate, confidence
limits for 60 percent and 90 percent chance were computed and drawn
on each figure. These confidence limits indicate that individual
predictions are subject to considerable uncertainty. The sol id
part of the limit 1 ine indicates the range of discharge best defined
from the data.

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The effect of bed grain size on the relation of width and velocity
to discharge was investigated for 40 stations by graphical multiple
regression. The effect of bed grain size was not found to be
significant.

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