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