How Do Rivers Begin? Rivers begin as trickles of water that run over the ground and join together in...

Chapter 2

Section 1

Streams and Rivers

How Do Rivers Begin?Rivers begin as trickles of water that run

over the ground and join together in larger streams.

Rain that falls can Evaporate immediately Soak into the soil as groundwater Form runoff (water that flows over the ground surface) that can eventually lead to a river.

Rain that falls…

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Time to review!

Factors That Affect Runoff1. The nature of the ground surface

(water passes through soil easier than cement, so grass/plants will slow water down as it is absorbed)

2. The rate of rainfall (a lot of rain can’t all soak in, so some becomes

runoff)

3. Whether the land is flat or hilly (water falls faster down a steep slope than over flat

ground, so the water moves too fast to be absorbed and forms a stream instead)

River SystemsThe smaller streams

and rivers that feed into a main river are called tributaries.

A river system is made of the main river and all of its tributaries.

WatershedsThe land area that supplies water to a river

system is called a watershed or drainage basin.

The Clinton River Watershed, which ends at Lake St. Clair is the nearest major watershed. However, the Great Lakes Watershed also impacts us as well.

* technically Grosse Pointe is considered “direct drainage” which means we drain directly into Lake St. Clair and not into a watershed

WatershedsOne watershed is separated by another by a

ridge of land called a divide, and streams flow in different directions on each side.

New Vocabulary WordsRiver Systems:Runoff TributaryRiver systemWatershedDivide

Rivers Shape the LandErosion is the process during which

fragments of soil and rock are broken off from the ground surface and carried away.

Rivers Shape the LandDeposition the process during which soil

and rock are left behind and build up.

How do rivers shape the land?Rivers wear away landforms through erosion and build new landforms through deposition.

With erosion, sediment is carried away.

Soil and rock are left behind with deposition.

New terms: erosion and deposition

Rivers Shape the LandRivers wear away landforms through erosion

and build new landforms through depositions.

The particles of rock and soil that are picked up and moved by erosion and deposition are called sediments.

Rivers Shape the LandThe faster the water flows, the more energy

it has to move heavier sediments.

Three factors affect a river’s speed: The steepness of the slope (steeper = faster) The amount of water in the river (more = faster) The shape of the channel (deeper/broader =

faster)

How fast is that river? Time to Review!

Factors affecting the speed of a

river

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Profile of a RiverThe many small

streams that come together at the source of the river are called the headwaters (usually fast, choppy, and narrow).

Profile of a RiverDownriver, the channel

becomes deeper and wider due to erosion, it is less steep, has more water in it from tributaries, and continues to move swiftly but much more smoothly.

The Flood PlainThe broad, flat valley (created by years of

erosion) through which the river flows is called the flood plain.

Profile of a RiverSmall obstacles in the river’s channel cause

the water to flow slightly to one side or the other, creating a bend in the river.

Profile of a RiverThe process of eroding and depositing

sediments on the curves of a river channel will gradually form loops called meanders.

Profile of a RiverThe crescent-shaped,

cutoff body of water that remains after a river breaks through the ends of a meander is called an oxbow lake.

https://www.youtube.com/watch?v=4qKS_Nk7UmY

Profile of a RiverThe mouth is the

point where a river flows into another body of water (a larger river, a lake, or an ocean).

Use the diagram below to answer #14 - #18:

Profile of a River

Profile of a RiverWhen the river hits the larger body of water

at the mouth, it instantly slows down.

This slow speed allows most of the river’s sediment to be deposited and build up at the river’s mouth, in an area called a delta.

Profile of a River

New Vocabulary WordsProfiles of a RiverHeadwatersFlood plainMeandersOxbow lakeMouthDelta

Rivers and FloodsA flood occurs when the

volume of water in a river increases so much that the river overflows its channel.

Precipitation can add more and more water to a river, making it faster and stronger.

Can Floods Be Controlled?

A dam is a barrier across a river that may redirect the flow of the river to other channels or store the water in an artificial lake.

Fear or welcome a flood?

Yeah flood!!!

Deposition leaves a layer of nutrient rich sediment behind.

Boo flood!Destroy farms and

cropsDestroy homes Loss of electricity,

transportation, clean water

Injury or death of people and livestock

Can Floods Be Controlled?Levees are long ridges formed by

deposits of sediments alongside a river channel. Man-made levees are also used to make natural levees stronger.

Can Floods Be Controlled?When Hurricane Katrina hit New Orleans, Louisiana in 2005, some of the levees broke and flooded large areas of the city.

When does a flood occur?

A flood occurs when the volume of water in a river increases so much that the river overflows its channel.

https://www.youtube.com/watch?v=RNde3bnXaVM

Fear or welcome a flood?

Yeah flood!!!

Deposition leaves a layer of nutrient rich sediment behind.

Boo flood!Destroy farms and

cropsDestroy homes Loss of electricity,

transportation, clean water

Injury or death of people and livestock

How can we control floods? Build a dam – a barrier across a river that

may redirect the flow of a river to other channels OR store the water in an artificial lake.

Levees – can be natural or people made. People can build up a natural levee with sandbags.

Vocabulary Words: dam and leveehttps://www.youtube.com/watch?v=oD4Q

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