River morphology and process class

1. River morphology and process class consider physics of flow and erosion review river taxonomy examine the germane processes that control the shape of river channels consider the graded profile consider the impact of floods and tectonic setting on river channels

2. Gravity = driving force Solar = energy source • Gravity responsible for movement of water down gradient, PE = mgh ~  h • Precipitation maintains supply of fluid, driven by solar forcing • Tectonics maintains gradient, driven by erosion and endogenic forces • Consider fluid forces acting on sediment, critical shear stress (crit, need to detach grains • Balance of erosion, sediment supply shapes channels 1

3. Hujlstom Diagram 1

4. 1

5. MODES OF SEDIMENT TRANSPORT • Sliding • Rolling • Saltation • SHOW FLASH MOVIE

6. Taxomony 2

7. Downstream Organization 2

8. Channel MobilityWatts Branch, MD 2/3

9. Flow is not uniform in plan view 3

10. Water velocity is not uniform with depth Consider friction and laminar flow; mean velocity at 0.6 d

11. Idealized flow patterns Alluvial, meandering river Dye tracing 3

12. Graded profile, idealized form • rivers will try and adjust to minimize energy gradient • tectonics and climate change get in the way

13. Can the river keep up? Gorges reflect cutting Knick zones reflect inability to cut quickly enough Taiwan

14. What does climate change do? Glacial hanging valleys, bedrock channel erosion

15. Gaysville before the flood

16. 1927 flood - Gaysville, VT - after