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rivers and streams

River Systems. A river or stream: any body of water flowing downhill in a well defined channel. Drainage basinDrainage divide. Divided into 3 subsystemsCollecting systemTransporting systemDispersing system. Stream System Order. -Tributaries decreases downstream-Tributary length increases downstream-Gradient decreases downstream-Channels are wider deeper downstream.

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rivers and streams

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    1. Rivers andStreams

    2. River Systems A river or stream: any body of water flowing downhill in a well defined channel

    6. Divided into 3 subsystems Collecting system Transporting system Dispersing system

    8. Stream System Order -Tributaries decreases downstream -Tributary length increases downstream -Gradient decreases downstream -Channels are wider deeper downstream

    12. Stream Flow Dynamics Factors affecting stream behavior Discharge (Q) Gradient Average velocity (V) Channel cross-sectional area (A) Load Base level

    13. Stream Flow Dynamics Discharge The volume of water flowing past a given point in the river Discharge will vary with time and weather conditions Measured in cubic meters per second

    15. Gradient The slope of the stream channel Change in elevation divided by distance (m/km) Longitudinal profile is a concave upward Steep at headwaters Nearly flat at discharge area

    18. Velocity varies within the channel Highest velocity is in the center of the channel Drag slows water along the bottom, banks, and top (water-air interface)

    20. Load Material carried along by the stream Suspended load (fine particles) or Bed load (coarse particles) Dissolved load (ions in solution)

    23. Base Level - level to which a stream will erode

    25. Stream Erosion River systems erode the land surface by: Removal of weathering products Downcutting of stream channel Headward erosion

    26. Downcutting of Channels Bottom of stream channel abraded by transported sand & gravel

    28. Headward Erosion Erosion rates are greatest where stream gradients are high

    32. Stream Deposition Floodplains Deltas Alluvial valleys and fans

    33. Meandering Streams Rivers flow in a sinuous pattern Turbulent flow & velocity changes eroded one bank, deposit on the other Erosion changes course of river

    37. Floodplains Floods Normal stage - water level below the bank Bankfull stage - water level even with the bank Flood stage - water level above the bank Floodplains Areas that will be submerged when a river is at flood stage

    38. Braided Streams Multiple channel system Interlaced channels with islands High sediment load Common in arid & semi-arid regions Seasonal high flows Common in front of glaciers Large sediment load, fluctuating water flow

    42. Alluvial Valleys Streams fill part of their valleys with sediment Changes in hydrologic conditions initiate deposition Subsequently cut through deposits Create terraces

    43. Deltas Formed by sudden drop in velocity Stream enters ocean or lake Stream drops sediment load Evolve by three mechanisms Growth may be influenced by ocean waves

    44. Delta Growth Distributaries Levee and in-stream deposit formation Channel splits into two smaller channels Splays Crevasse allow water to leave main channel Water spreads out forming a splay deposit Avulsion Shift in main course to follow steeper slope

    46. Alluvial Fans Accumulation of sediment in a dry basin Deposition due to rapid velocity drop Usually arid climate High sediment load - braided streams Form fan-shaped deposit

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