Outer Earth processes and systems - Physical Processes in Earth and Environmental Sciences - page 285

(b)

(a)

1 m

1 km

Rio Negro

Free-shear layer
with K-H vortices

Meghna

Padma

Rio Solimoes

Kelvin-Helmholtz mixing vortices
develop along high-velocity gradient of
free-shear zone

(c)

Trunk
channel

Indicative mean surface
velocity vectors

Crest of steep
confluence bar

Fig. 6.67 Turbulent mixing and scour at river channel tributary junctions highlighted when tributaries of contrasting suspended sediment con-
tent meet. Both the Negro (Amazon; a) and Meghna (b) rivers have low suspended sediment and high organic content. (c) Plan view schematic.

(a)

Levee slopes gently
out toward
floodbasin floor
floodbasin

Lake

(b)

Newly emergent channel bank levee (channel is c . 5m to the
left) to show pale deposits of fine sand from overbank flow

Crevasse splay breakout from channel levees

Fig. 6.68 Floodplain wetland processes. (a) shows storm on a freshly emergent levee (R. Ouse). (b) shows a crevasse breakout through levees
into a floodplain wetland (R. South Saskatchewan).