1. Landform Geography Fluvial Systems and Landforms

2. Overland Flow & Drainage Basins Hydraulic Geometry & Channel Flow Fluvial Processes & Landforms Human Interactions with Streams

3. Overland Flow Perennial Streams – water runs all year Ephemeral Streams – water runs only part of year Sources of stream water: –Groundwater –Melting Ice –Surface Runoff

4. Drainage Basins Drainage Basin – area contributing groundwater and runoff to a stream Drainage basins are divided from each other by topographic barriers called watersheds Drainage Divide – elevated terrain forming rim around a drainage basin Drainage basins vary tremendously in size Basins are nested, smaller within larger

5. Small, Nested Drainage Basins

6. Common Drainage Pattern Types

7. Major US Watersheds

8. Drainage Density Total length of all streams Drainage Density = Area of drainage basin

9. Stream Ordering Represents stream size Smallest streams in basin order 1 – order rises when 2 streams of same order come together at confluence

10. Hydraulic Geometry Geometric attributes of river channels Variables: –w = channel width –d = channel depth –v = velocity of water –s = slope (steepness) also called gradient –Q = discharge (amt of water flowing) –Q = w x d x v (units m 3 /s or ft 3 /s)

11. Hydraulic Variables

12. Stream Hydrograph Graph showing fluctuation in stream discharge over time Lag between storm event and highest discharge Base flow – flow rate sustained by groundwater influx

13. Flooding Flood Stage – stream discharge increases so that water spills out of channel onto adjoining ground Return Period – time between events of a given magnitude, e.g. annual flood, 50-year flood, 100- year flood Larger floods occur less frequently

14. Mississippi River Floods - 1993 At least 100-year flood, perhaps a 500-year flood Heavy winter rains saturated ground Stationary high pressure in Southeast in summer, blocking mid-latitude jet stream over Midwest Cool, dry air collided with warm, moist air along jet stream, creating constant precipitation Precipitation ran off into stream channels & rivers

15. Mississippi River Floods - 1993

16. 2009 Carrollton Floods

17. Fluvial Processes and Landforms Running water is most important geomorphic (landform shaping) process on Earth’s surface All landforms due to either erosion or deposition Erosional landforms occur when sediment, soil, or rock is stripped away from land Depositional landforms occur where sediment accumulates after being dropped

18. Depositional vs. Erosional Landforms

19. Hillslopes Most active zones of fluvial erosion due to high relief creating fast-moving, powerful water Rills Gully

20. Ravine Canyon

21. Landforms Geography Glaciers

22. Glacial Geomorphology Development of a glacier Types of glaciers Glacial landforms

23. Development of a Glacier

24. Glacial Mass Budget

26. Glacial Movement

28. Glacier Types

30. Continental Glaciers

31. Glacial Landforms Rock & debris picked up by glaciers, transported in direction of movement & deposited Glacial erosion: –Glacial Abrasion – scratch and gouge bedrock –Glacial Striations – caused by glacial abrasion –Glacial Grooves – deep striations –Glacial Plucking – boulders ripped from ground by glacier – deposited by retreating glacier, called Glacial Erratics

32. Glacial Erosional Landforms Glacial grooves Roche Moutonnee Glacial striations

33. Alpine Erosional Landforms Glacial Erosion: –Cirque – bowl-like feature on mountain flanks –Tarn – small lake in bottom of cirque –Arête – narrow, steep ridges between cirques –Horn – mountain with 3 or more arêtes at summit –Glacial Trough – u-shape valley eroded by glacier

34. Alpine Erosional Landforms

35. Glacial Depositional Landforms – Glacial Drift Glacial Till – sediment directly deposited by glacier – many particle sizes Moraine – winding ridge formed by till at the front or side of glacier – Moraine types: –Lateral – along former edges of glacier –Terminal – along front of former glacier –Recessional – formed as glacier recedes –Medial – between 2 glaciers –Ground – irregular deposition as glacier recedes

36. Glacial Depositional Landforms (Till)

37. Glacial Depositional Landforms (outwash) Glacial Outwash – sediments deposited by water out & under a glacier as it melts – forms Outwash Plain, flat feature in front of former glacier Kame – large mound deposited near glacier front Esker – winding ridge from water flowing in tunnel through ice under glacier Kettle Lake – big ice block fallen off glacier front is buried by outwash, melts later forming lake

38. Glacial Depositional Landforms