Summary
River systems are dynamic, constantly changing landscapes through processes like erosion, transportation, and deposition. Understanding river characteristics and the Bradshaw Model helps explain these changes from source to mouth.
- Long Profile — the side view of a river from its source to its mouth, showing the gradient. Example: Steep at the source, flatter at the mouth.
- Channel Width & Depth — measurements of how wide and deep a river is, increasing downstream. Example: Narrow and shallow in the upper course, wide and deep in the lower course.
- Velocity — the speed of water flow, usually increasing downstream. Example: Faster in the lower course despite a gentler gradient.
- Discharge — the volume of water flowing past a point per second, increasing downstream. Example: More tributaries join, adding water.
- Wetted Perimeter — the length of the riverbed and banks in contact with water, affecting friction. Example: More contact slows flow.
- Hydraulic Action — erosion by the force of water compressing air in cracks. Example: Dislodges material during high flow.
- Attrition — rocks carried by the river collide and break into smaller pieces. Example: Pebbles become rounder and smoother.
Exam Tips
Key Definitions to Remember
- Long Profile: Side view of a river from source to mouth.
- Discharge: Volume of water flowing per second.
- Hydraulic Action: Erosion by water force compressing air in cracks.
Common Confusions
- Why velocity increases downstream despite a flatter gradient.
- Difference between abrasion (erosion of bed/banks) and attrition (erosion of particles).
Typical Exam Questions
- Describe the changes in a river's characteristics from source to mouth? Mention gradient, discharge, channel width, and velocity changes.
- Explain why deposition occurs at location X? Link to decreased energy/velocity and sediment deposition.
- Explain how hydraulic action erodes the river channel? Define the process and describe the mechanism.
What Examiners Usually Test
- Understanding of the Bradshaw Model and river characteristics.
- Ability to explain processes like erosion, transportation, and deposition.
- Application of key terms in describing river features and changes.