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Landform Geography

Landform Geography. Fluvial Systems and Landforms. Fluvial Systems and Landforms. Overland Flow & Drainage Basins Hydraulic Geometry & Channel Flow Fluvial Processes & Landforms Human Interactions with Streams. Overland Flow. Perennial Streams – water runs all year

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Landform Geography

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  1. Landform Geography Fluvial Systems and Landforms

  2. Fluvial Systems and Landforms • 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 m3/s or ft3/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

  25. Glacial Mass Budget

  26. Glacial Movement

  27. Glacial Movement

  28. Glacier Types

  29. Continental Glaciers

  30. 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

  31. Glacial Erosional Landforms Roche Moutonnee Glacial grooves Glacial striations

  32. 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

  33. Alpine Erosional Landforms

  34. 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

  35. Glacial Depositional Landforms (Till)

  36. 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

  37. Glacial Depositional Landforms

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