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Rivers

Rivers. Why important? Flooding has tormented civilization for a long time. But… we continue to occupy low-lying regions adjacent to rivers. Must understand ENTIRE river system… not just the region occupied by water on most days. Drainage Basins: Where the water comes from.

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Rivers

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  1. Rivers

  2. Why important? Flooding has tormented civilization for a long time.

  3. But… we continue to occupy low-lying regions adjacent to rivers.

  4. Must understand ENTIRE river system… not just the region occupied by water on most days.

  5. Drainage Basins: Where the water comes from.

  6. Drainage Patterns

  7. Basic Terminology: Flood plain -area adjacent to river channel Streams and Rivers • Runoff-portion of moving across the surface • Drainage basin -area drained by single stream • Slope-gradient of a stream (drop/unit of length) • Longitudinal profile -plot of elev. vs. length • Cross-section- profile across a stream valley • Plan view- two dimensions, map view • Base level- lowest level that a stream can erode its bed • Stream power = discharge X slope X unit weight of water

  8. Measuring and Calculating Discharge • Continuity Equation • Discharge Q= V x A or V x W x D  blackboard example of conservation of discharge • Reach -river area under study

  9. Channel Patterns Channel Patterns • Braided • Meandering • Point bars • Riffles and pools • Oxbows • Anastomosing • Multiple channels • Gulf Coast (Fl, La) Riverine environment--the river and adjacent floodplain

  10. Channel Patterns – Braided Rivers Nizina river, Alaska

  11. Channel Patterns – Meandering River (forms & processes)

  12. Avulsion – “permanent” change in a river’s course 1952 1988 McMurdo Basin, Columbia River, B.C.

  13. Sediments in Rivers • Competence-largest particle a stream can transport • Capacity-total load a stream can carry • Streams and Rivers • Transport of rock cycle • Erosion and sediments • Total load • Suspended load • Bed load • Dissolved load

  14. Competence Diagram

  15. Velocity/Shear Stress, Erosion, and Deposits • Alluvial fan-change in slope • Bajada -coalescing alluvial fans • Delta -form at the mouth of some rivers • Distributaries -streams that flow on deltas

  16. Effects of Land Use Change • Change in stream profiles • Development • Dam construction Modification of Continuity Equation • Q = C x i x A (C = Coefficient of infiltration; i =intensity of rainfall; A-area)

  17. Florida Rivers

  18. Florida Rivers

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