Geography Chap 13

Select consequences to a river when a dam is contructed.

-the dam creates a temporary base level for the river -water released from the dam is clear (no sediment) and has a new capacity to erode and transport sediments downstream -the dam causes the river to deposit its sediment load upstream of the dam

Identify the factors that can begin or end a stream's existence.

-the slopes across which a stream flows change -the source of water or sediment supply changes -a change in the elevation of its base level occurs

Why does the discharge of a stream change during the course of a year?

-the type of precipitation can vary during the year -influx from groundwater can vary during the course of a year -the amount of precipitation can vary by season

In what ways do streams impact people's lives?

-they allow for the generation of energy without the release of carbon dioxide -they provide floodplains with nutrients required by plants and crops -they are used as transportation routes

Which of the following describe the headwaters of mountains streams?

-they have the ability to carry large boulders -they have steep gradients -they have turbulent flow

The erosional base level of a river can be ____.

-a lake -a closed land basin -an ocean

Stream formation or cessation

-changing the slope of the land can cause the formation or cessation of a stream -changing the amount of water or sediment supplied to a basin can cause the formation of a stream or cause its end

At a flow velocity of 12 cm/sec, which of the following statements are true?

-most sand sizes are trasported as bedload -clay is trasported as suspended sediment

What three factors of a dranage basin influence the flow response to rainfall?

-size -shape -slope

Select two ways that mountain streams obtain their sediments

-soil and/or sediment slides down into the drainage area -tributaries bring sediments into the drainage area

Select the characteristics of a braided river or stream.

-steep gradient -variable flow -abundant sediments

Rank in order from beginning the processes necessary to create entrenched meanders

1. a meandering river flows across a floodplain 2. a tectonic even causes an uplift, causing the river to erode downward 3. further incision by the river creates more entrenchment

Beginning processes necessary to create entrenched meanders

1. a meandering river flows across a floodplain 2. a tectonic event causes an uplift, causing the river to erode downward 3. further incision by the river creates more entrenchment

Rank the following particle sizes transported by water from smallest to largest.

1. clay 2. silt 3. sand 4. cobbles 5. boulders

Rank the formation of terraces by rivers from the first stage at the top to the last stage on the bottom

1. deposition of sediment occurs on the floodplain 2. a drop in the base level of the river results in downcutting through deposits 3. further downcutting occurs, and the river abandons the previously formed floodplain 4. the oldest floodplain becomes isolated as the river downcuts, leaving a terrace

What is a braided stream?

A stream that flows in a network of many interconnected rivulets around numerous bars

River effects on drainage system

Dam - changes the base level because of sediment buildup Tectonism - can increase the slope and supply of coarse sediments Runoff - increases flow, causing flooding Geology - streams erode soft rocks more easily than hard rocks Vegetation - plants stabilize stream bank and protect against erosion

What does a hydrologic gauging station do?

Measures and records real-time data about a stream's flow

dendritic drainage pattern

Treelike pattern develops on rocks with similar resistance to erosion

An oxbow lake is an isolated, curved lake formed when ____.

a meander is cut off from a stream

What is a point bar?

a sandbar deposited along the inside of stream meanders due to lower velocity

what is a drainage network?

a series of interconnected streams that when combined drains a larger area than any one stream

Oceans, lakes, or the bottoms of closed basins are all examples of ____ levels of rivers.

base

_____ are formed as rivers slow down when they reach their mouth and empty into an ocean

deltas

_____ are formed as rivers slow down when they reach their mouth and empty into an ocean.

deltas

When the amount of sediment exceeds the ability of the current to carry it, the stream _____ the sediment.

deposits

Structurally controlled pattern

drainage occurs on eroded layers or structures and then cuts across a ridge to follow a different weak layer

The gradient of a stream or river is defined as the change in ____ for a given horizontal distance.

elevation

Rivers and streams ____ the landscape, carry the materials, and later deposit the sediments, thereby acting as major sculptors of Earth's surface.

erode

A(n) ____ is an event in which the amount of water flowing through a river channel overflows its banks.

flood

The amount of discharge needed to overtop a stream's banks and spill onto the surrounding land is the _____ stage.

flood

A(n) _____ is a broad strip of land on either side of a stream channel that is covered by water during a flood and replenished by sedimentation.

floodplain

What is the word used to describe the change in elevation for a given stream or river over a horizontal distance?

gradient

The driving force behind a river's flow is ____.

gravity

The two primary forces that drive a river system are ___ and ___.

gravity; precipitation

In flowing water, the upstream side of an obstruction is subjected to the ____ of abrasion.

greatest amount

The area of the origin of a river is its ____, and the ____ the end of the river.

headwaters; mouth is

What does downstream mean?

it is the direction of flow in which the water is moving

The base level of a river is the ____ elevation to which the river can erode.

lowest

What type of lake is created when a cutoff meander becomes isolated? the answer is just one word

oxbow

A(n) ____ stream or river is one that flows year-round, whereas a(n) ____ stream does not flow the entire year.

perennial; ephemeral

A depositional feature that has been built on the inside of a curve because of lower velocity is a ____.

point bar

____ or bowl-shaped pits are created when flowing water and sediments swirl in small depressions.

potholes

how does rainwater cause erosion on the ground?

rain causes splash erosion as the drop hits the ground and flows over it, causing sheet erosion

when a stream's discharge rapidly rises above and then quickly falls below flood stage, it is known as a _____ flood.

rapid

Rafters enjoying a mountain river trip encounter both turbulent ___ and calm ___ located upstream of the turbulent areas.

rapids; pools

Erosion and deposition by ____ are the principal processes that sculpt Earth's landscape.

rivers

the type of sediment transport that involves a series of leaps or bounces off the bottom of a streambed is ____.

saltation

The amount that a river or stream channel curves in a given lenght is called its _____.

sinuosity

Rainwater creates ____ erosion as it hits the ground.

splash

Stream terraces are composed of either ____ or ____.

stream-derived sediment composing former floodplains; an erosional surface cut into bedrock

What are bedrock streams?

streams that are cutting into the bedrock of the area

River ____ are relatively flat benches that are perched above a river or stream and that stair-step upward and outward from the active channel.

terraces

Sinuosity refers to ____.

the amount that a river or stream channel curves in a given length

Smaller subsidiary channels that feed the main channels of rivers are ____.

tributaries

_____ is a property of a fluid that is defined as the resistance to flow.

viscosity

What is a flood?

water overflows a stream's channel

Landforms associated with the headwaters of mountain streams

waterfall - occurs when a stream or river's gradient is so steep that water goes over a ledge or cliff rapid - occurs along a river and is characterized by turbulent water lake - occurs where water is impounded by some obstruction pool - occurs when water slows down and piles up upstream of a rapid

Rank the seasons from the lowest discharge of water to the highest for a river located in the upper Midwest of the US.

1. winter 2. fall 3. summer 4. spring

Radial drainage pattern

Drainage is found on symmetrical mountains such as volcanoes

Condition to effect

dam - changes the base level because of sediment buildup tectonsim - can increase the slope and supply of coarse sediments runoff - increases flow, causing flooding geology - streams erode soft rocks more easily than hard rocks vegetation - plants stabilize stream bank and protect against erosion

A(n) ____ is formed where a river meets the sea, slows down, and deposits its sediments.

delta

The amount of water flowing through a channel over a given amount of time is called its ___.

discharge

Type of sediment load to description

dissolved - chemically soluble ions transported by the river suspended - clay and silt carried indefinitely above the riverbed bed - material carried on the bottom of a river by pushing, bouncing, rolling, and sliding; usually sand and gravel

A ridge or strip of high ground that separates one drainage basin from another is a drainage ____.

divide

On the outside of a meander, the water velocity is faster and causes ____, and on the inside of a meander, the water velocity is slower, which causes ____.

erosion; deposition

The largest rivers last ____ as features on the landscape.

for a long time