AS Geography rivers
- Created by: Matt14
- Created on: 14-04-15 09:47
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- Drainage basin & hydrological cycle
- This is the area drained by a river
- Rivers, floods & management
- Hydrographs
- Factors that affect discharge
- Vegetation
- Surfaces
- Soil / rock type
- Landuse
- Storm intensity
- Types of hydrographs
- Flashy (storm )
- variation in discharge over SHORT period of time
- Subdued
- shows variation in discharge over LONGER periods of time
- Flashy (storm )
- Key features
- Base flow
- Rising limb
- Peak discharge / flow
- Receding limb
- Lag time
- Factors that affect discharge
- River procesess
- Erosion
- Types of erosion
- Abrasion
- Hydraulic action
- Attrition
- Corrosion
- Vertical - more common in UC
- Lateral - more dominant in in M + LC
- Material is then transported and deposited
- Types of erosion
- Transportation
- Types of transportation
- Traction
- Suspension
- Solution
- Saltation
- Capacity- amount of material in a river
- Competence - diameter of largest particle (for given velocity)
- Types of transportation
- Deposition
- Occurs when there is not enough energy to carry the load
- Reduction of gradient
- Shallower water (meander inside bend)
- Flooding across the floodplain
- Reduced discharge (drier weather)
- Largest material is dropped first
- Velocity decreases
- Occurs when there is not enough energy to carry the load
- Erosion
- Hjustrom curve
- Shows relationship between velocity and particle size
- Higher velocity = more material carried (vv)
- smallest particles , only deposited at very low velocities
- more powerful waters needed to move small clay / silt as they stick togther
- once picked up many particles can be carried at a lower velocity than originally needed
- Also catergorises type of river load by size.
- Clay
- silt
- sand
- gravel
- pebbles
- boulders and cobbles
- Hydrographs
- Hydrological cycle
- Consists of: inputs , outputs, transfers and storages
- Examples: precipitation energy from sun
- evaporation transpiration (+ evapotranspiration)
- rivers lakes and sea/ocean
- stemflow infiltration and groundwater flow
- Balance between inputs & outputs = WATER BALANCE
- Formula : P = Q+E +/- changes in storage (S).
- Consists of: inputs , outputs, transfers and storages
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