ENVR 150 Hydrology Quiz

4-Dimensions of Streams

• Longitudinal Dimension: Measures the length of the stream.
• Lateral Dimension: Refers to the width of the floodplain.
• Vertical Dimension: Includes stream depth and hyporheic zones, where approximately 30% of river flow occurs underground via downwelling and upwelling.
• Time Dimension: Encompasses daily, seasonal, and annual variations in stream dynamics.

Stream Morphology

• Profiles: Characterized by slope and gradient from headwaters to base level.
• Patterns: Observations include:
  • Meandering: Common in floodplains, characterized by lateral movement.
  • Straight: Often unnatural, created by human interventions.
  • Braided: Common near glaciers with high sediment loads and minimal vegetation.
  • Anabranched: Complex systems with larger braids and vegetated islands.

Channel Types

• Alluvial Channels: Formed and modified by sediment transported by the river; highly dynamic.
• Non-Alluvial Channels: Maintained by bedrock or concrete, characterized by deep cuts into deposits.

Stream Profile

• Upper Reaches:
  • Features vertical erosion leading to V-shaped valleys.
  • Steep gradients with the presence of rapids, waterfalls, and lag boulders.
• Lower Reaches:
  • Involves lateral erosion resulting in U-shaped valleys.
  • Characterized by gentle gradients with terraces, floodplains, meanders, and point bars.

Base Level

• Defined as the level beyond which erosion ceases, significant in understanding river dynamics.
• Alluvial Fans and Deltas:
  • Formed at points where rivers meet level ground, creating distinct sediment deposits.

Fluvial Processes

• Erosion:
  • Removes weathered materials through physical (scouring, cavitation) and chemical processes (dissolution of minerals).
• Transportation:
  • Movement of materials categorized as bedload (saltation, traction), suspended load (turbidity), and dissolved load (conductivity).
• Deposition:
  • Occurs as the stream slows, depositing alluvium and forming floodplains, levees, and alluvial fans.

Fluvial Determinants

• Key Variables: Velocity, discharge, and turbulence determine a stream's capacity to carry sediment.
• Capacity: Maximum total load a stream can transport.
• Competence: Ability to move particles of specific sizes, indicated by D-95 and D-50, which measure particle size distribution.

Particle Size Classification

• Varies from boulders (>256 mm) to silt (<0.063 mm), with size generally decreasing downstream from rocky headwaters to sandy lowland rivers.