Land and Water, River Diversity Flashcards
Catchments (othersise known as drainage basins and watersheds)
The drainage area of a river network
Drainage divides
Ridges and hills of high altitude and relief that separate neighbouring catchment areas
How is drainage density calculated?
DD = Total length of all streams/Area of drainage basin
What are the five key principles of catchments?
- Longitudinal profile
- Sediment movement
- Source zone
- Transfer zone
- Accumulation zone
Longitudinal profile
The changing charcateristics (slope, width, depth) of a river as it moves donwstream
Sediment movement
The origin, transportation, and accumulation of sediment
Source zone
An area where rate of erosion greatly exceeds the rate of deposition
Transfer zone
An area where the the rate of erosion and deposition are roughly balanced
Accumulation zone
An area where the rate of deposition exceeds the rate of erosion
What are the three controls of river diversity?
- Slope
- Energy
- Sediment type and size
What are the four confinements of river types?
- Confined
- Partly confined
- Laterally unconfined (continuous channel)
- Laterally unconfined (discontinuous channel)
What are the two broad types of rivers?
- Bedrock (supply limted)
- Alluvial (transport limited)
What are the four characteristics of bedrock rivers?
- Dominated by erosional processes (low sediment supply)
- Fixed channel boundaries due to bed and banks being composed of bedrock
- High transport capacity but low storage capacity (limited accomodation space)
- Input is roughly the same as output
What are the four characteristics of alluvial rivers?
- Dominated by depositional proccesses (low transport capacity)
- Erodible channel boundaries (both banks and bed)
- High storage capacity
- Input is larger than output
How do bedrock rivers form?
Bedrock rivers form very slowly by angular rocks abrading the river bed, forming a steep terrain
How do alluvial rivers form?
Alluvial rivers are self-formed from the transport and deposition of sediment, changing according to different water and sediment conditions
Where are bedrock and alluvial rivers found
Bedrock: Source zones
Alluvial: Transfer and accumulation zones
What are the three measures of channel planforn (shape)?
- Number of channels
- Sinuosity
- Lateral adjustment of channel
What are the four main river types studied in this section?
- Braided
- Meandering
- Anastomosing
- Discontinuous watercourses
What are the four main characteristics of braided rivers?
- Diverging and converging channels separated by bars
- Laterally unstable channels
- Easily erodable, non-cohesive banks
- Dominated by depositional processes
What are the four main characteristics of meandering rivers?
- Single channel
- Well defined floodplains and cohesive banks
- Low sediment load
- Distinct outerbanks and point bars
What are the four main characteristics of anastomosing rivers?
- Multinchanneled
- Laterally stable channels separated by floodplain segments
- Cohesive banks
- Dominated by fine grained sediment
What are the four main characteristics of discontinuous watercourses?
- Has an absent or discontinuous channel
- Low slopes
- Suspended load of mostly fine sediment
- Includes wetlands, swamps, and chain of ponds
What are the three types of rivers when using sediment as a measurement?
- Bedload
- Suspended load
- Mixed laod
Bedload river
Comprised of sand and other coarser sediments. Has non-cohesive banks
Suspended load river
Comprised of mud, has cohesive banks
Mixed load rivers
Typically composite banks with suspended loads above bedload deposits
