What happens to rainfall What happens to rainfall when it hits earth????when it hits earth????

Some evaporatesSome evaporates Some is absorbed and becomes Some is absorbed and becomes

ground waterground water Some is run offSome is run off

Running WaterRunning Water

Running waterRunning water is the most is the most powerfulpowerful agent of erosion.agent of erosion.

Running water is Running water is abrasiveabrasive – it wears – it wears down rocks and makes them down rocks and makes them smaller, smaller, smoother,smoother, and rounderand rounder.. (USSR = U (USSR = U see Small, Smooth, Round).see Small, Smooth, Round).

How Does Running Water How Does Running Water Carry Sediment?Carry Sediment?

Running water carries sediment in Running water carries sediment in three ways:three ways:

1. 1. In solutionIn solution – things that are – things that are dissolveddissolved in the water.in the water.

2. 2. In suspensionIn suspension – very – very smallsmall sediment sediment like silt and clay that like silt and clay that hanghang or or dangledangle in in the water but never settle and won’t the water but never settle and won’t dissolve.dissolve.

3. 3. As bedloadAs bedload – sand, pebbles, – sand, pebbles, boulders that are rather boulders that are rather largelarge and and heavyheavy and travel along the and travel along the stream bedstream bed (bottom of the stream/river).(bottom of the stream/river).

Carrying Power of Running Carrying Power of Running WaterWater

Carrying powerCarrying power of running water of running water depends on its depends on its velocityvelocity (speed) (speed) and and dischargedischarge (amount of (amount of water).water).

The top of The top of page 6page 6 in your ESRT? in your ESRT? It shows how larger sediment It shows how larger sediment can only be transported by fast can only be transported by fast moving water.moving water.

PARTICLE SIZE vs. VELOCITYPARTICLE SIZE vs. VELOCITY Different sized Different sized

materials require materials require different water different water velocities to be velocities to be carried via carried via suspension, suspension, solution, or solution, or bedload. This is bedload. This is illustrated by the illustrated by the size/velocity size/velocity curve…curve…

Running Water GradientRunning Water Gradient

Running water has Running water has gradientgradient (slope).(slope).

The The steepersteeper the gradient of the the gradient of the stream/river, the stream/river, the fasterfaster the the water will water will flowflow..

Calculate the gradient Calculate the gradient of the following

stream: A stream’s source (where it begins) is found at 100 ft., 25

miles away is its mouth (where it ends) at 50 ft.

1. Gradient = change in field value

distance

2. G = 100 ft. – 50 ft.

25 mi.

3. G = 2 ft/mi.

The River ValleyThe River Valley River valleys River valleys

are are V-V-shapedshaped!!!!! !!!!! (Just (Just remember “V” remember “V” for valley).for valley).

V shape valley is evidence of running water.

The River ValleyThe River Valley

In the late maturity stage and In the late maturity stage and old ageold age stage of a river, the stage of a river, the valley will become valley will become flattenedflattened and and wide.wide.

The The olderolder rivers become the rivers become the more they more they meandermeander (bend) and (bend) and thus the thus the widerwider the valley the valley becomes.becomes.

Youth (very young river

Early Maturity

Late Maturity Old Age

Stages of Stream Stages of Stream DevelopmentDevelopment

Divides and Drainage Divides and Drainage BasinsBasins

A high piece of land that A high piece of land that separatesseparates one river valley from one river valley from another is called a another is called a dividedivide..

A river and all the tributaries that A river and all the tributaries that flow into a river is a flow into a river is a river systemriver system..

Drainage basins or Drainage basins or watershedswatersheds include all the include all the landland that drains that drains into the river system.into the river system.

WATERSHEDWATERSHED

Land from which water runs off into a Land from which water runs off into a stream.stream.

Tributary –Tributary – feeder stream that flows feeder stream that flows into a main stream.into a main stream.

Meanders and Oxbow Meanders and Oxbow LakesLakes

Water in a river or stream does Water in a river or stream does notnot move at the same move at the same speedspeed at at every point.every point.

As a river swings around a As a river swings around a bendbend, , the the fastestfastest moving water is on moving water is on the the OUTSIDEOUTSIDE of the bend.of the bend.

The The slowestslowest moving water is on moving water is on the the INSIDEINSIDE of the bend. of the bend.

Meanders and Oxbow Meanders and Oxbow LakesLakes

Because of this difference in speed, Because of this difference in speed, EROSIONEROSION occurs on the occurs on the OUTSIDEOUTSIDE of a of a river bend.river bend.

DEPOSITIONDEPOSITION occurs on the occurs on the INSIDEINSIDE of of river bends.river bends.

This will eventually create This will eventually create meandersmeanders or loops in the river.or loops in the river.

deposition

Meandering ChannelsMeandering Channels

Meanders and Oxbow Meanders and Oxbow LakesLakes

As this erosion and deposition As this erosion and deposition process continues and the meander process continues and the meander swings swings widerwider, the curve becomes a , the curve becomes a looploop..

The river eventually The river eventually breaksbreaks throughthrough and becomes a and becomes a cutoffcutoff..

The river begins to The river begins to depositdeposit more more sediment at the site of the cutoff and sediment at the site of the cutoff and the meander completely the meander completely separatesseparates from the river forming an from the river forming an oxbow lakeoxbow lake..

Oxbow Animations

http://www.school-portal.co.uk/GroupDownloadFile.asp?file=21606

Oxbow LakeOxbow Lake

Depositional FeaturesDepositional Features Since moving water can be very Since moving water can be very powerfulpowerful, ,

it has the power to it has the power to sortsort sediment. sediment.

Sediment gets sorted by Sediment gets sorted by sizesize, , shapeshape, and , and densitydensity..

Once the water Once the water slows downslows down, it , it depositsdeposits or or drops sediment it can no longer carry. drops sediment it can no longer carry.

The The largestlargest,, most dense sediment gets most dense sediment gets deposited deposited firstfirst,, then medium, then then medium, then smallsmall and less dense gets deposited last.and less dense gets deposited last.

Depositional FeaturesDepositional Features The The greatestgreatest loss of speed that can loss of speed that can

occur is when a river empties into occur is when a river empties into an an oceanocean. .

It is literally like it hits a It is literally like it hits a brick wallbrick wall..

It It “throws-up”“throws-up” all the sediment it’s all the sediment it’s been been carryingcarrying..

One example of this is a One example of this is a river river deltadelta..

DeltasDeltas

Deltas are triangle shape.

Nile River Delta

Nile River Delta at Night

How’s it going to sort itself.

Drops the biggest sediment first

Last ?

Depositional FeaturesDepositional Features

If it were not for the If it were not for the Mississippi Mississippi RiverRiver depositing all the sediment depositing all the sediment into the into the Gulf of MexicoGulf of Mexico, the city , the city of of New OrleansNew Orleans would not be. would not be.

This is why New Orleans is This is why New Orleans is considered to be considered to be below sea levelbelow sea level, , it lies on a delta.it lies on a delta.

Is this triangle Is this triangle shape?shape?

Depositional FeaturesDepositional Features

In In mountainousmountainous regions, often a regions, often a river or stream will just empty river or stream will just empty into the bottom of the mountain into the bottom of the mountain where it is where it is drydry..

When this happens, the sediment When this happens, the sediment spreads outspreads out and creates an and creates an alluvial fanalluvial fan..

The Flood PlainThe Flood Plain A A floodflood occurs when water occurs when water spillsspills over over

the sides of a river or stream’s the sides of a river or stream’s banksbanks..

During floods, thick During floods, thick depositsdeposits build-up build-up alongside the stream banks, this alongside the stream banks, this forms forms leveeslevees..

Beyond levees, the flood plain is Beyond levees, the flood plain is lowerlower and and swampsswamps form.form.

Flood plains are very Flood plains are very fertilefertile (vegetation grows well) because they (vegetation grows well) because they get so much get so much mineralsminerals and and nutrientsnutrients deposited there during floods.deposited there during floods.

RAPIDS AND RAPIDS AND WATERFALLSWATERFALLS

Rapids Rapids - Different resistance among - Different resistance among rocks cause FAST-FLOWING WATER rocks cause FAST-FLOWING WATER

Waterfalls Waterfalls – Rapids develop into – Rapids develop into waterfalls as softer rock erodeswaterfalls as softer rock erodes

Typical Erosion of Waterfalls