Chapter 12: River Systems and Landforms

Transcription

1 Chapter 12: River Systems and Landforms

2 Base Levels: Local and Ultimate Figure 12.6

3 Figure 12.2 A Drainage Basin

4 Rills and Gullies feeding into small Streams in Iowa

5 North American Drainage Basins Figure 12.3

6 Rough outline of the Columbia River drainage basin

7 Landscape Drainage Patterns Treelike pattern Folded topography Volcanoes Steep slopes/relief Figure 12.5 Faulted & Jointed Structural domes No clear geometry

8 Figure Fluvial Transport

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10 GIA 12: pp Meandering Stream Profile

11 Meandering Stream Development GIA 12: pp

12 Itkillik River, Alaska Cutoff GIA 12: pp

13 Athabasca River, Alberta

14 Horseshoe Bend: an entrenched meander along the Colorado River

15 Tasman River, New Zealand Braided stream channel

16 Figure Map of Carter Lake, Iowa

17 Rivers don t make good political boundaries, as indicated by the floodplain

18 Stream Longitudinal Profile: Graded Streams Greater erosion Greater deposition Figure 12.15

19 Development of a graded stream: progression to a local base level

20 Development of a graded stream: progression to a local base level

21 Development of a graded stream: progression to a local base level

22 Streams get wider, deeper, and faster as you move downslope from the headwater source regions then flatter in slope

23 Figure Nickpoint in Stream Channel

24 Niagara Falls: current location of the nickpoint

25 Palouse Falls

26 Tangle Falls, British Columbia

27 Figure Typical Floodplain Features

28 Sebaskachu River, Labrador

29 Alluvial Terraces of the Rakaia River, New Zealand Rejuvenation of the stream via regional uplift often creates these terraces, since the stream still downcuts and sidecuts Figure 12.21

30 12.24: Nile River Delta

31 12.23: Mouths of the Ganges

32 Rapaalven River, Sweden: river infilled an entire lake with its delta, creating a braided channel within this former glacial valley

33 Disaster Planning for Rivers: Weather Forecasting, Dams, Levees, Monitoring

34 Figure 12.9 Streamflow Measurement

35 Figure 12.8 Flooding: Urban vs. Natural Landscapes

36 Flooding Near McCall, April 2002

37 Pacific Northwest: Built by Volcanics, Sculpted by Floods, Winds, Ice

38 Glacial Dam: Moreno Glacier, Patagonia

39 Moreno Ice Dam Failure: Outburst Flood [jahkollops]

40 Glacial Lake Missoula: multiple lakes were created by the intermittent advance of ice sheets during the last Ice Age as the various ice dams failed, massive floods swept across northern Idaho and eastern Washington

41 On Highway 195 Outside Spokane: Missoula Flood Deposits

42 Notice how vegetation on left-hand slope protects, while exposed slope erodes...

43 Still along Highway 195, on the right as you approach Spokane

44 Glacial Lake Missoula s flood deposits are being reworked by fluvial processes, a perfectly natural [but undesirable] reality.

45 Coping with erosion: using a dike -like structure to armor the toe of the slope against stream erosion processes.

46 Lake Bonneville: massive, single flood that rechanneled the Snake River

47 View from ancient shoreline of Glacial Lake Bonneville

48 A little closer to Moscow at the confluence of Snake and Clearwater Rivers are the cities of Lewiston on the left, and Clarkston on the right. The arrow is roughly where Atlas Sand & Gravel is located the business is mining flood deposits from the Lake Bonneville flood about 14,500 years ago the Great Salt Lake is what is left of former Lake Bonneville

49 Atlas Sand & Gravel: some material doesn t need crushing

50 Meander cutoff Structure: little change Oxbow lake formation Shrinking lakes Reoccupying old channel Disappearing lakes

51 Walker River, Sierra Range