A Level Physical Geography - The Hjulstrom Curve

Introduction

This tutorial will guide you through understanding the Hjulstrom Curve, a crucial concept in physical geography that illustrates the relationship between sediment size and the velocity needed for erosion, transportation, and deposition. This knowledge is essential for A-Level geography students and can help in exam preparation.

Step 1: Understand the Basics of the Hjulstrom Curve

• The Hjulstrom Curve is a graph that plots sediment size against the velocity of water flow.
• Key components of the curve include:
  • Erosion: The process by which particles are removed from the riverbed or banks.
  • Transportation: The movement of sediment downstream.
  • Deposition: The settling of sediment in a new location.

Practical Tips

• Familiarize yourself with terms like "sediment" (small particles of rock and soil) and "velocity" (the speed of water flow).

Step 2: Analyze the Hjulstrom Curve Graph

• The graph typically has sediment size on the x-axis and flow velocity on the y-axis.
• Key points on the curve include:
  • Erosion Threshold: The minimum velocity needed to erode particles of different sizes.
  • Transportation Zone: The range of velocities where particles are actively transported.
  • Deposition Threshold: The minimum velocity required for the particles to settle.

Common Pitfalls to Avoid

• Confusing the different zones; remember, erosion occurs at higher velocities for larger particles, while smaller particles can be eroded at lower velocities.

Step 3: Examine the Factors Affecting Sediment Movement

• Several factors influence sediment movement, including:
  • Particle Size: Larger particles require more energy to move.
  • Water Velocity: Higher velocity can transport larger sediments.
  • Water Density: Denser water can carry more sediment.

Real-World Applications

• Understanding the Hjulstrom Curve can aid in predicting river behaviors during floods and in sediment management for construction projects.

Step 4: Practice Questions and Applications

• To reinforce your knowledge, consider these practice questions:
  • What is the relationship between sediment size and the velocity of water flow?
  • How does the Hjulstrom Curve apply to river management?

Practical Exercise

• Sketch your own Hjulstrom Curve and label the zones of erosion, transportation, and deposition. Use different sediment sizes to illustrate the thresholds.

Conclusion

The Hjulstrom Curve is an essential tool for understanding sediment dynamics in rivers. By grasping the concepts of erosion, transportation, and deposition, you can better prepare for your A-Level geography exams. Moving forward, practice applying this knowledge to real-world scenarios and engage with further resources available on educational platforms.