Chapter 12: River Systems and Landforms

Base Levels: Local and Ultimate Figure 12.6

Figure 12.2 A Drainage Basin

Rills and Gullies feeding into small Streams in Iowa

North American Drainage Basins Figure 12.3

Rough outline of the Columbia River drainage basin

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

Figure 12.11 Fluvial Transport

GIA 12: pp. 386-87 Meandering Stream Profile

Meandering Stream Development GIA 12: pp. 386-87

Itkillik River, Alaska Cutoff GIA 12: pp. 386-87

Athabasca River, Alberta

Horseshoe Bend: an entrenched meander along the Colorado River

Tasman River, New Zealand Braided stream channel

Figure 12.14 Map of Carter Lake, Iowa

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

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

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

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

Figure 12.17 Nickpoint in Stream Channel

Niagara Falls: current location of the nickpoint

Palouse Falls

Tangle Falls, British Columbia

Figure 12.19 Typical Floodplain Features

Sebaskachu River, Labrador

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

12.24: Nile River Delta

12.23: Mouths of the Ganges

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

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

Figure 12.9 Streamflow Measurement

Figure 12.8 Flooding: Urban vs. Natural Landscapes

Flooding Near McCall, April 2002

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

Glacial Dam: Moreno Glacier, Patagonia

Moreno Ice Dam Failure: Outburst Flood [jahkollops]

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

On Highway 195 Outside Spokane: Missoula Flood Deposits

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

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

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

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

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

View from ancient shoreline of Glacial Lake Bonneville

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

Atlas Sand & Gravel: some material doesn t need crushing

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

Walker River, Sierra Range