Fluvial Morphology: Landforms Made by Running Water

What is the most important geomorphic agent shaping the landscape?

RUNNING WATER Rivers and Streams

What is the work of rivers and streams?

Erosion Transportation Deposition

Fluvial Morphology:Study of Landforms Made by Running WaterFLUVIAL: from the Latin fluvins for ‘running water’ or streamflow

Fig. 17-3, p. 472

The Long Profile of Streams•At their headwaters, the grade of a stream is usually steep. •At Mid-streams, the angle of the grade becomes more gently sloping.• Near the mouth of the stream, the grade becomes almost flat.

Fig. 17-11, p. 480

Stream StagesStream StagesStreams also show three stagesstages of gradation from the mountains to the sea, with associated erosionalerosional and depositionaldepositional features:

Youth

Maturity

Old Age

Stream Stage 1 - YouthCharacteristics of Youthful Streams

Steep irregular profileWaterfalls, rapids, and plunge poolsRiver is deepening its channel Cutting into bedrockV-shaped cross-section

• The Cycle of Erosion

Youthful stage•headward erosion and •vertical downcutting dominant

• steep stream gradients promote valley deepening

• narrow, V-shaped valleys

1.The channel at upstream point A-B 2.This channel is located in the stream's headwaters. 3.The stream gradient and surrounding topography is quite steep. 4.Stream velocity is at a maximum and cuts a narrow deep channel. 5.The floodplain is minimal as high velocities carry all sizes of load down stream. 6.Stream load is high as the steep gradient provides the energy for extensive erosion7. Producing a V-shaped river valley.

Fig. 17-1a, p. 470

Fig. 17-CO, p. 468

Waterfalls and Rapids

Hard rock layers have not yet been smoothed awayA waterfall is a vertical drop in a streambedRapids are stream sections with extremely strong currents.Both are sites of vigorous erosionPotential Hydro Electric Power

Stream Stage 2 - Mature ValleyCharacteristics of Mature Valley Streams

Valley widening beginsMeandering StreamFloodplains

Fig. 17-21, p. 487

 

Figure c-d: Stream channel near the middle of a typical stream profile.

 

•The channel is now leaving the mountainous terrain and entering a landscape that is more gently sloping. •Causes a sudden reduction in the stream's velocity. •The stream adjusts to this change, by depositing most of its coarse stream load onto the floodplain. •The stream also takes on a braided channel form. •These channels are always changing in size, number, and location

Lateral Erosion - Valley Widening Begins Erosion is greatest on the outside bend

Cut-banksDeposition on the inside bendMeanders

Widen the valleyForm cutoffs Create oxbow lakes

Fig. 17-22a, p. 488

Fig. 17-24a, p. 489

Stream Stage 3 - Old AgeCharacteristics of Old Age Streams

Wide Alluvial Valley StageNatural Levees

Depositional featureParallel to the stream channel on both banks

 

The channel near the mouth of the stream (Figure E-F). Extensive flat floodplain is composed of Deposits from channel meandering. The channel is quite large and U-shaped. Stream discharge is at a maximum and sediment load is generally composed of finer materials.

Fig. 17-26, p. 491

A river cut-off results in a portion of the river isolated from the new channel called an oxbow

Rivers drop their load when they enter the ocean and form a ________?

  Deltas Large deposit of alluvial sediment located at the mouth of a stream where it enters a body of standing water.

http://www.youtube.com/watch?v=AjZLAw_lgZ4&feature=related

Fig. 17-27b, p. 491

Deltas are created when the sediment load carried by a stream is deposited because of a sudden reduction in stream velocity.

Mississippi Birdfoot Delta (Source: NASA).

Fig. 17-27a, p. 491

. Some deltas, like the Nile, have a triangular shape

Ganges River DeltaImage taken 2/28/2000 The Ganges River forms an extensive delta where it empties into the Bay of Bengal. The delta is largely covered with a swamp forest known as the Sunderbans, which is home to the Royal Bengal Tiger.   The Ganges River Delta can be found on Landsat 7 WRS Path 137 Row 44, center: 23.12, 90.37.

p. 494

Drainage Basins (Watersheds)

Fig. 17-5, p. 475

p. 474

Lake Itasca is a small glacial lake, approximately 1.8 square miles (4.7 km²) in area, in the Lake District of Northwestern Minnesota.

It is the Source[1] of the Mississippi River.

Table 17-1, p. 479

Los Angeles River Now!

2005

http://www.youtube.com/watch?v=ta35C488dnE

http://www.ilike2learn.com/ilike2learn/Rivers/Longest%20Rivers.html

Is this river aggrading or degrading? Is it near the headwaters or the delta?

Is this river aggrading or degrading? Is it near the headwaters or the delta? Aggrading, at the delta

Is this river aggrading or degrading? Is it near the headwaters or the delta?

Is this river aggrading or degrading? Is it near the headwaters or the delta? Graded, near the middle or end of its course.

Missouri River, MO

Is this stream aggrading or degrading? Is it near the headwaters or the delta?

Is this stream aggrading or degrading? Is it near the headwaters or the delta? DEGRADING, NEAR THE HEADWATERS

Canadian Rockies

Stage Landscape Processes

Youthful Steep hillsides,drainage divides

predominant, V-shaped valleys

Headward erosion,stream downcutting –

vertical erosion

Mature Rounded hills, valley walls predominant,

graded streams,broad floodplains

Lateral erosion, streams adjust to

discharge/loadmeandering

Old age Floodplains, ox-bow lakes,deltas and alluvial plains,

very low reliefDeposition,

sluggish stream flow,poor drainage

Fluvial Processes and Landscapes at Different Stream StagesFluvial Processes and Landscapes at Different Stream Stages