Landform Geography

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Landform Geography
Fluvial Systems and Landforms
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Fluvial Systems and Landforms

• Overland Flow Drainage Basins
• Hydraulic Geometry Channel Flow
• Fluvial Processes Landforms
• Human Interactions with Streams

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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

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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

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Small, Nested Drainage Basins
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Common Drainage Pattern Types
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Major US Watersheds
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Drainage Density
Total length of all streams
Drainage Density
Area of drainage basin
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Stream Ordering

• Represents stream size
• Smallest streams in basin order 1 order rises
  when 2 streams of same order come together at
  confluence

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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)

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Hydraulic Variables
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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

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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

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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

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Mississippi River Floods - 1993
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2009 Carrollton Floods
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Fluvial Processes and Landforms

• Running water is most important geomorphic
  (landform shaping) process on Earths 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

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Depositional vs. Erosional Landforms
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Hillslopes

• Most active zones of fluvial erosion due to high
  relief creating fast-moving, powerful water

Rills
Gully
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Ravine
Canyon
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Landforms Geography
Glaciers
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Glacial Geomorphology

• Development of a glacier
• Types of glaciers
• Glacial landforms

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Development of a Glacier
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Glacial Mass Budget
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Glacial Mass Budget
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Glacial Movement
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Glacial Movement
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Glacier Types
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Continental Glaciers
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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

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Glacial Erosional Landforms
Roche Moutonnee
Glacial grooves
Glacial striations
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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

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Alpine Erosional Landforms
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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

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Glacial Depositional Landforms (Till)
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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

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Glacial Depositional Landforms