1.2 CHANNELS Flashcards
Topology
Channel networks
Chanel network
Result of landscape formation in the past and the preferred route of water to flow in the present.
Natural ones formed efficiently: minimal energy use
Most common: dendric pattern (tree shaped)
Geomorphology
origin of the landscape and channels
Drainage density
Quantifies the abundance of channels.
Length of channels(m)/ a certain area(m^2)
High density: area contains many channels (per km^2)
> so the average distance from a location on land to nearest channel is small
Climate, humans, geology soil and land cover affect drainage density
AREAS OF HIGH DRAINAGE DENSITY
Drainage density high in areas of low soil conductivity: water has to flow over the ground-> if that happens often channel is shaped
Agricultural areas: man made, Specially in lowland areas where water has to be discharged quickly.
Drainage patterns
Often relate to the geology
Dendric pattern: in landscapes with homogeneous geological formations-> many tributaries (branches)
Radial pattern: stream starts at central point, flows into all directions
Trellis pattern: In areas with folds in the earth crust.
Relatively large number of channels that have the same direction on each side of the river
The parallel pattern: on steep slopes where water flows downhill.
Network ordering
Channel network can be divided into
- links: channel segments
- junctions: locations where channels merge
Source: location where a channel starts
Links between source and first junction: exterior links
Links between two junctions: interior links
Outlet: end-point downstream
Strahler order numbering method
- All exterior links get order 1
- When links of same order merge, +1 for the link downstream
- When links with a different order merge -> link downstream same number as the highest order of merging links
- Highest outlet always at the outlet: Strahler order of the catchment
