Geoscience Reference
In-Depth Information
Drainage divide separates
drainage basin from others
Mountain belt with
steep valley walls,
bedrock channels,
alluvial channels, and
narrow floodplains
(see also Chapter 2)
Tributary
Main channel
Alluvial fans as
main channels
emerge from
mountain belt
Distributary
Broad, low-relief valleys
with alluvial channels and
floodplains
Delta
Lake or sea
Fig. 3.2 Plan geometry of a hypothetical river system. (Based on Bridge 2003, fig. 1.1.)
(a)
(b)
Fig. 3.3 Photographs of river channel types. (a) LANDSAT image of the Brahmaputra River in Bangladesh. This is a very large sand-bed
braided river, flowing from north to south down the photograph. On the floodplain on either side are sinuous rivers that act as
distributary and tributary channels draining the floodplain. (b) LANDSAT image of the anastomosed Meghna River in Bangladesh,
where the sinuous river channels divide and rejoin around areas of floodplain and are separated for more than one meander wavelength.
Width of photographs is approximately 60 km. (Photographs donated by A. Carter.)
or islands. Some fluvial sedimentologists group
the straight and meandering types together as
'single channels', and the braided and anastomos-
ing types together as 'multiple channels'.
The planform geometry of rivers is controlled
by climate, tectonics and land-use, and more spe-
cifically by the rate of flow, flood-related sedi-
mentary processes and the amount of sediment
discharge (Schumm 1968; Knighton 1998). Little
channel change occurs during low flows and low
amounts of sediment transport. By contrast, the
increases in discharge and sediment transport
Search WWH ::




Custom Search