FLOOD05589

• County: Statewide
• Community: Statewide
• Stream Name: All
• Basin: Statewide
• Title: Ephemeral Streams Hydraulic Factors and Their Relation to the Drainage Net
• Date: 1/1/1956
• Prepared For: State of Colorado
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

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PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RlVEfiS

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EXPLANATION

o Various arroyos ntar SanlaFe
X Calienle Arroyo principa~ channels (coarse sand)
" 5th of July Wash (steep rills in smallgravelj
C Calienle Arroyo (rills in line gra~el and coarse sand)
V Road.cutrills (sand and fine gravef)
. Natural rills (sandandlinegfa'lel)

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CHANNEL WIDTH, IN FEET

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FIIWRE lB.-Relation of channel slope to channel width. Data from moderate and large arroyos and differentiated from rills b)' the dlft'erent s)'IIlbols. Number beside
point is serialldentitlcatlon keyed to data in appendix.

The manner in which discharge increases with
stream order is of particular concern, as it provides the
link between the Hort<)Il analysis and the hydraulic
geometry. For perennial streams, gaging-station data
are available in quantity for the larger stream orders.
The determination of stream order at a gaging station
is 'laborious but can be made, and order can be plotted
directly against discharge of a given frequency derived
from gaging-station data. In arid regions there are
relatively few gaging stations, and for the most part
they are located on the larger streams. To obtain a
relation between order and discharge for ephemeral
streams requires discharge measureInent.s of the smaller
streams. But even these measurements do not provide
at a given cross section a specific value of discharge
which can be plotted against stream order, for it
must be remembered that discharge at any given loca-
tion may fluctuate through a wide range and that
sufficient record is required to allow some kind of fre-
quency analysis.

If the discharge chosen has some specific relation
to the position of the cross section along the length
of the stream! an approximation t.o constant. frequency
might result. It is proposed to use that discharge
which c.orresponds to the average width representative
of the stream order at the point in question. To obtain
this value, the relations already demonstrated can be
utilized, Specifically, the relation between width and
order indicated on figure 19 will be combined wi th the
relat.ion of downstream increase of width \vith increas-
ing discharge. The latter is, fortunately, one of the most
consistent of the graphs representing the hydraulic
variables. From figure 19 the stream width for each
order can be obtained and, by use of those values of
width, the corresponding discharges can he read from
the width-discharge graph of figure 11. In such a
manner the relation between stream order and discharge
may be derived, and it is plotted as the unbroken line
on figure 20.