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

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the short straight reaches connecting the bends. At low flows, the local

slope is steeper and velocities are larger in the crossings than in the pool.

At low stages, the thalweg is located very close to the outside of the bend.

At higher stages, the thalweg tends to straighten. More specifically, the
thalweg moves away from the outside of the bend encroaching on the point bar

to some degree. In the extreme case, the shifting of the current causes

chute channels to develop across the point bar at high stages.

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2.2.1.4 The Continuum of Channel Patterns

Because of the physical characteristics of straight, braided, and

meandering streams, all natural channel patterns intergrade. Although braided

and meandering patterns are strikingly different, they actually represent

extremes in a continuum of channel patterns.

A number of studies have quantified this concept of a continuum of chan-

nel patterns. Lane (1957) investigated the relationship among slope, discharge,
and channel pattern in meandering and braided streams and observed that an

equation of the form

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SQl/4 = k

(2-1)

fits a large amount of data from meandering sand streams. Here, S is the

channel slope, Q is the mean annual discharge which can be approximated by
a two-year peak discharge, and k is a constant. Figure 2-2 summarizes

Lane's plots and shows that if

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SQl/4 ~ 0.0017

(2-2)

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a sand-bed channel will normally exhibit a meandering pattern. Simi1ari1y,
when

SQl/4 ~ 0.01

(2-3)

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a river tends toward a braided pattern. The region between these values of

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