Figure 5.17. Types of multi-channel streams.
The braided stream may present difficulties for highway construction because it is unstable,
changes its alignment rapidly, carries large quantities of sediment, is very wide and shallow
even at flood flow and is, in general, unpredictable.
5.4.5 River Conditions for Meandering and Braiding
It can be shown that changes in water discharge, sediment discharge or both can cause
significant changes in channel slope (see Section 5.5). The changes in sediment discharge
can be in quantity, Qs, or sediment size, D50, or both. Often, such changes can alter the
planview in addition to the profile of a river.
According to Lane (1957), Figures 5.18a and b illustrate the dependence of sand bed river form
on channel slope and discharge. They show that when:
S Q 0.25 ≤ k
(5.1)
where:
k
=
0.0007 SI
k
=
0.0017 English
a sandbed channel meanders. Similarly, when:
S Q0.25 ≥ k
(5.2)
5.21
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