AS Geography rivers

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  • 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
        • Key features
          • Base flow
          • Rising limb
          • Peak discharge / flow
          • Receding limb
          • Lag time
      • 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
        • Transportation
          • Types of transportation
            • Traction
            • Suspension
            • Solution
            • Saltation
          • Capacity- amount of material in a river
          • Competence - diameter of largest particle (for given velocity)
        • 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
      • 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
    • 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).

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