Running water
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Running water. 97.2 % oceans 2.2 % ice 0.6 % liquid fresh water most of which is ground water Water is always on the move in the water cycle. Water Cycle. Infiltration = soak in run off - surface flow evaporation = back into the atmosphere transpiration = back into the atmosphere by plant

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Running water

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Running water

Running water

  • 97.2 % oceans

  • 2.2 % ice

  • 0.6 % liquid fresh water most of which is ground water

  • Water is always on the move in the water cycle


Water cycle

Water Cycle

  • Infiltration = soak in

  • run off - surface flow

  • evaporation = back into the atmosphere

  • transpiration = back into the atmosphere by plant

  • evapotranspiration - combined


Running water1

Running water

  • Run off begins as sheet flow.

  • How much goes into the ground depends on the infiltration capacity of the soil

  • Factors of infiltration

    • intensity and duration of rain fall

    • soil wetness(saturation)

    • soil texture

    • slope

    • vegetation


Running water2

Running water

  • Rills - tiny channels

  • Gullies - larger channels

  • stream - any running body of water

    • sometime called rivers if really large


Stream characteristics

Stream characteristics

  • Gradient or slope is the vertical drop of the stream over a fixed horizontal distance,

    • The steeper the slope the more energy available for stream flow.

  • Cross-sectional shape determines the amount of drag.

    • The less drag the faster the water can flow

    • Size and roughness also influence drag


Stream characteristics1

Stream characteristics

  • Discharge is the amount of water flowing past a certain point in a given amount of time

    • Discharge (meter 3/ second)=

    • channel width(meters) X depth (meters) X velocity (meters/second)


Changes downstream

Changes downstream

  • Longitudinal profile - a look at the stream from head to mouth

    • gradient decreases downstream

    • discharge increases downstream

    • width, depth and velocity increase downstream

  • When gradient is high, discharge is small


Base level

Base level

  • Running water in a stream will erode downward over its course until it reaches a balance point.

  • This balance point is called the base level.

  • Base level is the lowest elevation to which a stream can erode.

  • Two types of base level


Base level1

Base level

  • Ultimate base level - sea level

  • Temporary ( local) base level - anything which has the capacity to limit downward erosion.

    • Lakes, resistant bedrock, or a larger stream

  • Kalamazoo River

    • Ultimate base level the Atlantic ocean

    • Local base level Lake Michigan


Base level2

Base level

  • Base level can be changed.

    • Raised base level results is velocity dropping and deposition begins up stream.

    • Lowered base level results in velocity increasing and erosion increasing.

  • How do you raise base level? Build a dam.

  • How do you lower base level? Uplift the land or lower sea level.


Base level3

Base level

  • Sooner or later a stream will reach base level and be neither eroding or depositing just transporting.

  • A graded stream is at base level


Stream erosion

Stream Erosion

  • Waters in streams are turbulent. They whirl and eddy.

  • The material in streams (sand, gravel, silt, and clay sized particles, plus dissolved minerals) abrades the streambed and become rounder and smoother with transport. This is called the load.

    • Potholes are gouged by gravel caught in an eddy.


Stream transport

Stream Transport

  • Dissolved load - minerals dissolved by ground water and added to the stream.

  • Suspended load - usually the largest load of a stream. Fine sand, silt and clay sized particles.

    • How much suspended sediment depends on velocity of the stream and settling rate of the sediment.


Stream transport1

Stream Transport

  • Bed Load - the material on the stream bed too large to be carried by suspension.

    • This is the stuff that does the grinding to produce downward erosion.

  • This material moves by rolling, sliding and saltation.

    • Saltation is jumping or skipping down stream


Stream transport2

Stream Transport

  • The ability to carry material is measured in capacity and competence.

  • Capacity is the maximum load a stream can carry.

  • Competence - the maximum sized particle a stream can carry.

    • The greater the stream’s discharge the greater the capacity and competence.


Stream deposition

Stream deposition

  • When velocity slows the stream can no longer carry its load.

  • Particles will be deposited by size with the largest settling out first.

  • This sorting explains why particles of the same size are found together.

  • Alluvium is the term for all stream deposited sediments


Stream deposition channel

Stream deposition - channel

  • Channel deposits - the materials deposited mid-stream usually sand or gravel in bars.

  • Point Bars form in the inside bend of a stream meander.

  • Braided streams have bars mid channel.

    • Merger of two streams with different velocity,

    • after glacial melting, or

    • after heavy down pour.


Stream deposition floodplain

Stream deposition- floodplain

  • Floodplain - the area adjacent to a stream that is covered with water during a flood.

  • Natural levees flank the stream and are an accumulation of gravel deposited during a flood when the water lost it competence and capacity upon leaving the channel.


Stream deposition floodplain1

Stream deposition- floodplain

  • Some levees are so high that tributary streams can’t enter the main stream.

  • These streams (Yazoo tributaries ) flow along the flood plain of the larger stream in swampy (back swamp) poorly drained areas.


Stream deposition fans and deltas

Stream deposition- Fans and Deltas

  • When a stream loses its competency abruptly it will drop its load.

  • Alluvial fans will form if the deposition occurs on land. These are fairly steep.

  • Delta will form if the deposition occurs under water.These are fairly shallow.


Stream deposition fan

Stream deposition- Fan

  • Alluvial fans form when a high gradient stream in a narrow mountain valley enters a broad flat basin.

  • The change is gradient is drastic resulting is immediate deposition.

  • Coarse material is deposited at the top of the fan while finer material is carried lower.


Stream deposition delta

Stream deposition- delta

  • Deltas form when a stream enters a lake or the ocean.


Stream deposition delta1

Stream deposition- delta

  • The main stream will become sediment choked, so it will seek a higher gradient route to base level.

  • It may do so by splitting into branches called distributaries.


Stream deposition delta2

Stream deposition- delta

  • Mississippi River Delta - a bird-foot delta.

    • This delta extends far out into Gulf of Mexico .

    • Many Smaller sub deltas have grown since the ice age.

  • Threat to the Mississippi includes a potential capture and diversion of water further upstream.

  • Could spell disaster for New Orleans.


Stream valleys

Stream Valleys

  • Playfair’s law - all streams have a main trunk, fed by branches and have carved the valley in which they exist.

  • Two types of stream valleys

    • narrow V shaped valleys

    • wide valleys with flat floors


Stream valleys v shape

Stream Valleys - V shape

  • Characterized by

    • downcutting

    • narrow canyons with steep wall

    • rapids and waterfalls

  • Valley walls undergo weathering and mass wasting at the top to help with the profile.


Stream valleys wide valleys

Stream Valleys - Wide valleys

  • More common in a graded stream

  • Erosion shifts from down-cutting to lateral.

  • Streams flow in floodplain is sweeping bends called meanders.

  • Erosion takes place on the outside of the bend at the cut bank.

  • Deposition takes place on the in side of the bend at the point bar

  • Causes the meander to migrate laterally and downstream


Stream valleys wide valleys1

Stream Valleys - Wide valleys

  • Sometimes one meander will cut off another to create a shorter channel

  • The abandoned meander is called an oxbow lake.

  • Eventually the lake fills with sediment to create a cut off scar

  • Incised meanders- form when there is a rapid change in base level.


Drainage networks

Drainage networks

  • All streams drain to an ocean.

  • The drainage basin is all the land contributes water to the stream.

  • A divide is the imaginary line that separates two drainage basins.

  • Individual drainage basins have one of four patterns depending on the material on which they flow.


Drainage patterns

Drainage Patterns

  • Dendritic - the most common - tree like branches emptying into larger trunks

  • Radial - like spokes on a bike tire draining the side of an isolated cone or dome.

  • Rectangular - flowing over jointed rocks making sharp right angle turns

  • trellis - also rectangular but looking more like a trellis with lots of branches.


Stream piracy ahrg

Stream Piracy - Ahrg!!

  • Streams erode headward, downward and laterally.

  • As Niagara Falls erodes it is doing so up stream (headward erosion)

  • When the headward erosion of one stream breaches the divide it can divert water from a slower stream. This is stream piracy.


Floods and flood control

Floods and Flood Control

  • What causes floods? Too much water from rain or melt water.

  • Controls include building artificial levees, dams,channelization (dredging) and better flood plain management (non-structural controls).


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