how do rivers begin? rivers begin as trickles of water that run over the ground and join together in...
TRANSCRIPT
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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