1. River systems

2. Runoff vs. Infiltration Factors determining runoff, or infiltration 1.Soil composition & pore space Coarse-grains & lots of humus = good infiltration Very fine-grains & poor humus = bad infiltration 2.Rate of precipitation Hard fast rain won’t soak in easily Slow steady rain infiltrates 3.Vegetation Abundant vegetation allows water to soak in 4.Slope steepness Steep slopes = more runoff

3. Tributaries- the main stream and feeder streams Water shed- the land from which the water runs off into the stream Divides- The elevated regions of land that separate watersheds.

4. Drainage Basins 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

5. Illinois Drainage Basins

6. The drainage basin of the Mississippi River

7. Drainage patterns

8. Stream and Channel Erosion Stream load- the materials carried by a stream Suspended load: Consists of fine particles like sand and silt Dissolved load: Mineral matter that’s dissolved and transported in the water solution Bed load: the larger more coarse material carried by the stream (sand, pebbles, rock)

9. Important River Terms Discharge - the volume of water moved by a stream in a given time Gradient - the change in elevation of a stream over a given horizontal distance Headwaters - the beginning of a stream Mouth- end of the stream system

10. Stages of a River - Youthful River Has a V-shaped valley with steep sides Waterfalls and rapids are common features Steep gradient High Velocity water (high discharge)

11. Stages of a River - Mature River Has well established tributaries and caries a large volume of water. Developing floodplain Meanders - a series of wide curves in river channel Oxbow lake - water that remains when meander is cut off from new river channel

13. Stages of a River - Old River The gradient and velocity decrease (flat land) Wide river bed Well established floodplain More meanders develop

14. 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

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

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

17. Same satellite view during flooding in 1993

18. Comparison of 1988 & 1993