Long profiles

• What are the three river courses?

  Upper, Middle, Lower
• What factors change from a river's source to its mouth?

  • Depth
  • Velocity
  • Discharge
  • Load
  • Particle size
  • Channel roughness
  • Gradient
  • Width
• What does the hydraulic radius measure?

  Efficiency of a river
• How is hydraulic radius calculated?

  Cross sectional area / wetted perimeter
• What effect does a higher wetted perimeter have on hydraulic radius?

  It lowers the hydraulic radius
• What is discharge in the context of rivers?

  Volume of water at a point
• What are the characteristics of the upper, middle, and lower courses of a river?

  Upper Course:

  • Highest gradient
  • Predominantly erosion

  
  

  Middle Course:

  • Middle gradient
  • Transportation

  
  

  Lower Course:

  • Lowest gradient
  • Deposition
• What are the valley cross-section shapes in river courses?

  • Upper Course: V-shaped valley
  • Middle Course: Gentle shaped valley
  • Lower Course: Flat and wide floodplain
• What are the channel cross-section characteristics in river courses?

  • Upper Course: Narrow and deep
  • Middle Course: Wider and medium
  • Lower Course: Wider and shallow
• What are some features of each river course?

  • Waterfall
  • Interlocking spurs
  • V-shaped valleys
  • Meanders
  • Oxbow lake
  • Floodplain
  • Levees
• How do depth, width, velocity, channel roughness, load amount, load size, discharge, gradient, and deposition change from upper to lower course?

  • Depth: shallow to deepest
  • Width: narrow to widest
  • Velocity: slow to fastest
  • Channel roughness: roughest to smoothest
  • Load amount: least to most
  • Load size: most to least
  • Discharge: least to most
  • Gradient: highest to least
• What are the types of erosion and their characteristics in river courses?

  • Erosion Types:
  • Vertical: Upper course
  • Lateral: Middle and lower courses
• What is capacity in the context of rivers?

  Maximum volume of load a river carries
• What is competence in river terminology?

  Maximum size of load a river carries
• What factors affect erosion rates in rivers?

  • Load: Heavier and sharper increases erosion
  • Velocity: Higher velocity increases erosion
  • Gradient: Higher gradient increases erosion
  • Geology: Soft rocks erode easily
  • pH: More acidic water increases solution
  • Human impacts: Deforestation, dams, bridges increase erosion
• What is denudation?

  Erosive process of breaking and removing rocks
• How can the rate of land erosion be calculated?

  By examining sediment and solute loads
• What factors lead to high sediment load and erosion?

  • Steep slopes
  • High rainfall
  • Tectonic instability
  • Deep loess deposits
  • Lack of vegetation cover
  • Climate
• What is cavitation in river processes?

  Collapse of vapor bubbles under pressure
• Why do rivers deposit their load?

  • Shallow gradient slows velocity
  • Decrease in water volume
  • Increase in friction with channel sides
  • Low flow rates due to low precipitation
  • River meets sea
  • Areas of low velocity (meander bend)
  • Broken banks lead to flooding
  • Load size exceeds river's capacity
• When does deposition occur in rivers?

  When rivers can no longer transport load
• What does the Hjuström curve illustrate?

  • Relationship between particle size and velocity
  • Erosion velocity curve for particle transport
  • Settling velocity curve for particle deposition

  
• What are the three important features of the Hjuström curve?

  • Smallest and largest particles need high velocities
  • Higher velocities needed for entrainment than transport
  • Particles are deposited when velocity falls below a certain level
• What does the critical erosion curve show?

  Minimum velocity to lift a particle
• What does the critical deposition curve indicate?

  Maximum velocity before particle deposition
• What is the energy requirement for sediment transport?

  • More energy is needed to lift sediment than to maintain it in transport
  • More energy is needed to erode small particles like clay