FLOOD01169

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Design Guidelines and Criteria Channels and Hydraulic Structures on Sandy Soil
• Date: 6/1/1981
• Prepared For: UDFCD
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Educational/Technical/Reference Information

10

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SQ1/4 can be considered a transitional range when streams are classified as

intermediate or transitional.

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2.2.1.5 The Longitudinal Profile

The longitudinal profile of a stream shows its slope or gradient. Since

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a river channel or river system is generally steepest in its upper regions,

most river profiles are concave upward. Shulits (1941) provided an equation

for the concave horizontal profile in terms of distance along the stream

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s = S
x 0

-aX
e

(2-4)

where, S the slope at any station a distance X downstream of reference
x station,
S = the slope at a reference station J
0
a = a coefficient of slope change.
Similarily, the bed material normally reduces in size downstream. The change
in particle size with distance downstream can be expressed as

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.

-sx
D50x = DSOo e

(2-5)

where,

DSOx

= median size of bed material at distance
reference station, feet,

x

downstream of a

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D500 = median size of bed material at the reference station, feet,

s

= a wear or sorting coefficient that is dependent on river
characteristics and flow conditions.

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It is clear that these exponential functions can only give a very general

idea of the longitudinal bed profile. The general curve is disturbed by

the presence of bends. Hence, the longitudinal slope of the thalweg will

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never completely follow a simple functional relationship. Moreover, the

presence of confluences and tributaries influences the main river as far

as bed level and grain size are concerned.

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