In addition to channel and bank characteristics, floodplain characteristics must also be
incorporated into an analysis procedure. The floodplain characteristics that should affect
meander migration include geologic controls, alluvial deposits and topographic variability.
Geologic controls include bedrock outcrops and erosion resistant features along the valley
sides. Alluvial deposits frequently include oxbows, meander scrolls and scars, and clay
plugs, each with different erodibility characteristics. Topographic variability that should be
considered include the cross valley slope of the adjacent floodplain and valley slope. These
factors could be incorporated into regression equations but would be difficult to include in
computer modeling of bendway migration.
5.9 SOLVED PROBLEMS RIVER MORPHOLOGY AND RESPONSE
5.9.1 PROBLEM 1 Meandering and Braiding
(a) Consider the sinuous point bar stream in Figure 5.31. Determine the following
meander amplitude A; and the bend deflection angle φ.
Figure 5.31. Sinuous point bar stream.
Meander wavelength λ is approximately 11,000 ft (3,353 m)
Radius of curvature rc is approximately 2,400 ft (732 m)
Channel width ranges from 250 ft to 850 ft (76 to 260 m) at high stage
Meander amplitude A is 2,200 ft (670 m)
Meander width Wm is 2,700 ft (823 m)
Bend deflection angle φ is 105
Sinuosity is 1.2
3
(b) Given the sand size D50 = 0.5mm, the bankfull discharge Q = 10,000 cfs (283 m /s) and
-4
the slope S = 2x10 , determine the effect of increasing slope, discharge, sediment size and
sediment discharge on the planform geometry.
5.67
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