Chapter 12: River Systems and Landforms
Preamble to Chapter 12
Base Levels:
Local and
Ultimate
Figure 12.6
A Drainage Basin
Figure 12.2
Rills and Gullies feeding into small Streams in Iowa
Rills and Gullies
North
American
Drainage
Basins
Figure 12.3
Rough outline of the Columbia River
drainage basin
Columbia River Drainage Basin
Landscape Drainage Patterns
Figure 12.5
Treelike pattern Folded topography Volcanoes
Steep slopes/reliefFaulted & Jointed Structural domes No clear geometry
Fluvial Transport
Figure 12.11
Size
Meandering Stream Profile
GIA 12: pp. 386-87
Meandering Stream Development
GIA 12: pp. 386-87
Itkillik River, Alaska
GIA 12: pp. 386-87
Cutoff
Athabasca River, Alberta
Bar
Horseshoe Bend: an entrenched meander along the Colorado River
Entrenched Meander
Tasman River, New Zealand
Braided stream channel
Braided Stream
Map of Carter Lake, Iowa
Figure 12.14
Rivers don’t make good political boundaries, as indicated by the floodplain…
ISS Photograph of Carter Lake
Stream Longitudinal Profile:
Graded Streams
Figure 12.15
Greater erosion Greater deposition
Development of a graded stream: progression to a local base level
Graded Stream: No Development
Development of a graded stream: progression to a local base level
Development
Development of a graded stream: progression to a local base level
Graded Stream: Well-Developed
Streams get wider, deeper, and faster as you move downslope from
the headwater source regions… then flatter in slope
Some Stream Characteristics
Nickpoint in Stream Channel
Figure 12.17
Niagara Falls: current location of the nickpoint
Niagara Falls
Palouse Falls
Palouse Falls
Tangle Falls, British Columbia
Tangle Falls
Typical Floodplain Features
Figure 12.19
Sebaskachu River, Labrador
Well-Developed Floodplain
Rejuvenation of the stream
via regional uplift often creates
these terraces, since the stream
still downcuts and sidecuts…
Alluvial Terraces of the Rakaia River, New Zealand
Alluvial Terraces
Figure 12.21
12.24: Nile River Delta
Nile River Delta
12.23: Mouths of the Ganges
Ganges Delta
Rapaalven River, Sweden: river infilled an entire lake with its delta, creating a braided
channel within this former glacial valley
Braided Stream/Delta
Disaster Planning for Rivers:
Weather Forecasting,
Dams, Levees, Monitoring
Urban Flood Planning
Streamflow Measurement
Figure 12.9
Flooding: Urban vs. Natural Landscapes
Figure 12.8
Flooding Near McCall, April 2002
Flooding near McCall, Idaho
Pacific Northwest: Built by Volcanics, Sculpted by Floods, Winds, Ice
Pacific Northwest River Landscapes
Glacial Dam: Moreno Glacier, Patagonia
Glacial Dam: Patagonia
Moreno Ice Dam Failure: Outburst Flood [jahkollops]
Jahkollops: Patagonia
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
Glacial Lake Missoula Overview
On Highway 195 Outside Spokane: Missoula Flood Deposits
GLM Deposits 1
Notice how vegetation on left-hand slope protects, while exposed slope erodes...
GLM Deposits 2
Still along Highway 195, on the right as you approach Spokane
GLM & Development 1
Glacial Lake Missoula’s flood deposits are being reworked by fluvial processes,
a perfectly natural [but undesirable] reality.
GLM & Development 2
Coping with erosion: using a “dike”-like structure to armor the toe of the
slope against stream erosion processes.
GLM & Development 3
Lake Bonneville: massive, single flood that rechanneled the Snake River
Glacial Lake Bonneville Overview
View from ancient shoreline of Glacial Lake Bonneville
GLB Ancient Shoreline
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
GLB, Lewiston & Clarkston
Atlas Sand & Gravel:
some material doesn’t need crushing
GLB, Atlas Sand & Gravel
Structure: little change
Reoccupying old channel
Oxbow lake formation
Shrinking lakes
Meander cutoff
Disappearing lakes
Remote Sensing Connection
Walker River, Sierra Range
Fluvial Landscape