Themes of the Day:

• Features of Rivers & Streams
• Quantifying River Behavior
• Discussion: Taming Rivers - Pros and Cons

Features of Rivers & Streams

• Drainage Basins, Streams, Rivers, Source (Headwaters), Mouth, Tributaries, Distributaries
• Valley, Flood Plain, Channel, Bed, Banks
• Braided Rivers - choked with sediment (glacial outwash, deserts)
• Meandering Rivers - usually low gradient
  Features:
  • Meandering channel
  • Cutbanks - erosion on outside of a meander bend
  • Point Bars - deposition on inside of a meander bend - sand and gravel deposits
  • Levees - natural (or artificial) embankment between river and flood plain - Development A -> B -> C
  • Cutoff - when a river short circuits a meander bend
  • Oxbow Lake - a cutoff meander bend - will often silt up
  • Flood Plain - flat lying areas adjacent to river subject to flooding during high water - often well suited for agriculture - silt and mud deposited here
• Deltas
  Features:
  • Distributaries
  • Topset, Foreset, and Bottomset beds
  • Progradation
  • Delta abandonment, migrating deltas - Mississippi vs. Atchafalaya
• Alluvial Fans

Quantifying River Behavior

• Gradient = slope = change in vertical elevation/change in horizontal distance
• Velocity is a function of slope and roughness of bed (friction)
• Laminar flow vs. Turbulent flow
• Discharge = volume per unit time = velocity*cross sectional area
• Velocity vs. Sediment Grain Size
• Types of Sediment:
  • Dissolved Load - ions such as Ca²⁺ and Na⁺
  • Suspended Load - fine clastic particles such as silt and clay
  • Bed Load - by traction or saltation - medium to coarse clastic particles such as sand or gravel
• Competence - largest size particle a stream can carry
• Capacity - total amount of sediment a stream carries past a point in a given period of time
• Flood Frequency