Fluvial Geomorphology Flashcards
(28 cards)
Definition of a watershed
forms an imaginary dividing line between 2 drainage basins.
Drainage basin boundary
this forms the catchment area of the basin
Confluence
the point where 2 or more streams meet along the course of a river
Source
the origin of a river, in the catchment area
Interfluve
the area between two tributaries, which are about to form a confluence point.
Hydrological cycle
Runoff and infiltration -> evaporation -> precipitation
Permanent rivers
- receive water all year
- water table always lies above the river bed
Periodic rivers
- have a base flow that only contributes during the rainy season
- Below wet water table, on the dry water table
Episodic rivers
- never supplied with groundwater
- only flows after a heavy downpour, causing flash floods
- base flow above wet and dry water table
Exotic rivers
- rise in high rainfall areas, but flow mostly through dry regions
- groundwater does not contribute
- base flow above wet and dry water table
Laminar flow
when the river bed is very level and even, velocity is low, water moves in thin layers
- Flows in sheets
- No eddies
- Smoothness reduces friction and thus turbulence
- Usually a gentle gradient
Turbulent flow
When the velocity of the river increases or if the river bed is uneven, a more irregular, whirling flow results
- Water forms eddies and bubbles
- Seethes down the slope
- Friction causes turbulence
- Gradient is steeper and erosion takes place
Types of river loads
Solution load = minerals and dissolved substances
Suspension load = fine insoluble particles in suspension
Bed load = heavier particles bounce along bed, called saltation
Bed load = heaviest pebbles and boulders, rolled and shoved down stream - traction
Factors affecting flow hydrograph
- Size of the basin
- Shape of the basin
- Relief
- Underlying rock and soil
- Climatic features
- Vegetation cover
- Human impact
Transverse vs Longitudinal profile
T = shows shape
L = side view
Temporary base level
Changes in gradient along the course of a river where vertical erosion is slowed
Headward erosion
a river lengthens its course by cutting back upstream above its original course
Mass movement
Movement downslope of weathered material
Abstraction
Process whereby the watershed becomes lower and its positions shifts
Attrition
An erosional process where rocks and pebbles are carried in the flow of a river and repeatedly knock into each other, which causes the rocks to erode or break. They continue to erode, getting smaller until they are only sediment.
Inter- vs Intra- basin transfer
the transfer of water from one basin to another distinct basin or river catchment
Upper course
- deep, narrow
- vertical erosion
- low volume and load
- turbulent flow
Middle course
- wider
- lateral erosion (over vertical)
- Increased volume and load
- less turbulent, more laminar
Lower course
- broad, flat
- deposition
- increased volume and suspended load
- laminar flow
