HJULSTRÖM CURVE

• WHAT IS IT?

  relationship between velocity and particle size
• WHAT IS ENERGY NEEDED FOR?

  erode (velocity)

  transport eposit

  deposit

  (different sizes of load)
• LARGER PARTICLES REQUIRE…


  more energy to erode or transport
• EROSION NEEDS…

  more energy than transport

  -> once particle is eroded it doesn’t require much energy to transport it
• WHAT DO HJULSTRÖM CURVES SHOW?

  small clay and a silt particles require more energy to lift (erosion)- energy to transport is low
• WHY THIS ANOMALY

  clay particles have a natural cohesion

  -> sticking together requires more energy to lift (erode them)

  clay particles can be tightly packed

  -> flow will be smooth with little friction

  ->Clay less likely to be disturbed by water
• COMPETENCE

  max size of material which the river is capable to transport
• CAPACITY 


  total load actually transported
• WHAT HAPPENS WHEN VELOCITY IS LOW

  only small particles (clay and silt) can be picked up
• WHAT HAPPENS IN INCREASED VELOCITY

  larger material can be moved
• MEAN OR CRITICAL EROSION VELOCITY CURVE

  approx velocity needed to pick up or transport in suspension, particles or different sizes
• MEAN FALL OR SETTLING VELOCITY 


  particles of a given size are to heavy to be transported -> fall from suspension and be deposited