Freshwater Flashcards
(44 cards)
Types of inputs in the drainage system
- precipitation (rainfall etc)
Types of outputs
- water, sediment, energy
What are the processes in the drainage basin
- Erosion
- Deposition
- Transportation
Where is water stored
Lakes, acquirers, dams, vegetation
Types of flows
Rainfall, infiltration, throughflow
Describe infiltration
When water is absorbed by soil
Describe surface run-off
Water flowing over surface
Describe throughflow
When water flows in soil though natural pipes.
Describe interception
When water in the plants is evaporated
Define discharge and the equation
- amount of water passing in a given time
EQUATION= CROSS SECTIONAL AREA X MEAN VELOCITY. - increases downstream
Describe turbulent stream flow
- water does not move steady
- high velocities
Describe laminar stream flow
- water moves steady
- low velocities
What channel characteristics affects discharge
- Cross sectional area— as river moves downwards it increased
- Velocity increases as river moved down.
Describe the processes of erosion
- ABRASION: wearing away bed from load being carried
- ATTRITION: load smash against each other
- HYDRUALIC ACTION: force of water and air relished river bank
- SOLUTION: materials are dissolved because of chemicals in the water
Factors affecting erosion
- Load particle size
- Velocity
- Human impacts
Describe the processes of transportation
- suspension: fine particles are carried by river
- traction: large builders are carried in river.
- saltation: small pebbled bounce along.
- solution: minerals dissolved in water.
What are the causes of deposition
- When the river slows down it looses energy
- When volume of water in channel decreases.
What does the Hjulstrom curve show
- relationship between velocity and particle size
The type of particle affects the velocity
Terms:
1. Entertainment velocity—> velocity needed to pick up load
2. Fall—>velocity needed to deposit load.
Describe how are waterfalls formed
- Soft rocks eroded quicker than hard rock
- Hard rock is left overhanging—> falls down into plunge pool
- Hydraulic action causes more erosion
- Waterfall retreats up creating a gorge.
How are floodplains formsed
- Erosion + deposition
- Interlocking spurs are removed via erosion and flow material is deposited due to loss of speed in water.
- Height of floodplain increases
Describe the formation of oxbow lakes
- erosion in the outside bend of meander due to increase in velocity
- deposition in the inside bend of meander due to decrease in velocity.
- river bends forming meander
- when meander cuts it created an oxbow lake.
Describe delta formation.
When water descends from river it looses energy
- forms distributaries to the sea.
Levees formation
- when there is flooding, water deposits sediment
Cresting leaves at each side of river
As there is more flooding the height of levees increases.
Characteristics of a hydrograph.
Rising limb→ incline of discharge curve, rising flood water in river
Steep rising limb→ rate of infiltration into soil cannot absorb volume of water
Peak flow→ max discharge in river
Recession limb→ decline of discharge
Basin lag time→ difference between peak and flow of river.
Overland flow→ downward movement of water
Throughflow→ lateral unsaturated flow of water in soil
Base flow→ normal discharge
Banffull discharge in river that fills stream channel without spilling
