1. Stream Channel Geology

2. Stream Channel Behavior CCCChannel shape and Velocity Less contact with channel = greater velocity Deeper narrow channels = high velocity Shallow wide channels = low velocity Higher velocities away from channel sides and bottom

3. Stream Channel Velocities

4. Channel Shape VVVValley sides are shaped by Weathering Mass Wasting Overland flow

5. Narrow Valleys CCCCharacteristics of narrow valleys V-shaped Down-cutting toward base level Features often include Rapids Waterfalls Stream is near base level Downward erosion is less dominant Stream energy is directed from side to side

6. Adjusting to Base Level

7. A narrow V-shaped valley

8. Continued erosion and deposition widens the valley

9. The resulting wide stream valley is characterized by meandering on a well- developed floodplain

10. Wide Valleys CCCCharacteristics of wide valleys Floodplain Features often include Meanders Cutoffs Oxbow lakes Sinuosity: windy-ness of a stream channel More meanders = high sinuosity

11. Highly Sinuous River

12. Anatomy of a Meander  Point bar Inside portion of a meander Inside portion of a meander Deposition due to low velocity Deposition due to low velocity Shallow Shallow  Cut bank Outside portion of a meander Outside portion of a meander Erosion due to higher velocity Erosion due to higher velocity Deeper Deeper

13. Erosion and deposition along a meandering stream

14. A meander loop on the Colorado River A meander loop on the Colorado River

15. Formation of a cutoff and oxbow lake

16. Floods & Flood Control Occur when discharge exceeds channel capacity Floods are the most common geologic hazard Causes of floods Weather Human interference with the stream system

17. Floods and flood control Engineering efforts Engineering efforts Artificial levees Artificial levees Flood-control dams Flood-control dams Channelization Channelization Nonstructural approach through sound floodplain management Nonstructural approach through sound floodplain management

18. Satellite view of the Missouri River flowing into the Mississippi River near St. Louis

19. Same satellite view during flooding in 1993

20. Comparison of 1988 & 1993

21. Drainage Basins DDDDrainage basins and patterns Drainage basin: land area that contributes water to the stream A divide separates drainage basin Types of drainage patterns Dendritic Radial Rectangular Trellis

22. Illinois Drainage Basins

23. The drainage basin of the Mississippi River

24. Drainage patterns