Chapter 16: Streams and Flooding

Rank in order from the beginning (at the top) the 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. (Place the smallest particle size at the top.)

1) Clay 2) Silt 3) Sand 4) Cobbles 5) Boulders

Match the feature with its description. Natural arch

A large opening that goes all the way through a narrow panel of rock

What is a bedrock stream?

A mountainous stream flowing through a carved bedrock channel

Match the feature with its description. Fin

A narrow panel of rocks that is the result of weathering controlled by joints on both sides

What is a point bar?

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

Match the feature with its description. Window

A small opening that goes all the way through a narrow panel of rock

What is a braided stream?

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

These are formed when a steep drainage enters a broad valley and the sediments and debris are deposited.

Alluvial fans

What is a natural bridge?

An arch-shaped features that span a (former) stream

______ are formed as flowing water collects in natural cracks or low spots. Once formed, these capture additional runoff within the drainage basin.

Channels

Select the answer that is not a factor in the deposition of deltas.

Chemical makeup of sediment

What types of sediments or rocks are deposited by low-relief streams?

Clay Silt Sand

Steep slopes in a(n) narrow canyon plus an unusually large thunderstorm resulted in the 1976 Big Thompson River flood near Estes Park in the state of ____________________ , just outside of Rocky Mountain National Park.

Colorado or CO

Select conditions that have an effect on the flow of river systems over time.

Dams Climate Tectonism Geology Runoff

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

Deltas

Which of the following physical parameters show an increase from the headwaters to the mouth of a river?

Discharge Channel size Sediment load

Match the river drainage pattern with the appropriate description of its geology. Radial drainage pattern

Drainage is found on symmetrical mountains such as volcanoes.

Match the river drainage pattern with the appropriate description of its geology. Structurally controlled pattern

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

Which of the following locations would be the two most common areas in which to find a braided stream or river?

Flat-bottomed valleys between mountains Broad, sloping plains that flank mountain ranges

What is a very common and important geologic agent in eroding, transporting, and depositing large amounts of sediment daily?

Flowing water

What types of streams typically deposit clay- to sand-sized sediments?

Low-relief streams

Which of the following physical parameters show a decrease from the headwaters to the mouth of a river?

Maximum grain size

During the 1993 flood on the upper ____________________ River, floodwaters flowed onto the floodplain because levees did not hold the water back. It took months for the floodplains to dry out because the __________________ trapped the water, preventing it from flowing back into the river channel.

Mississippi, levees

Select the conditions that caused the 1976 Big Thompson River flood near Estes Park, Colorado.

Narrow canyon Steep slopes of the river canyon Unusually severe thunderstorm

Define the landforms associated with the headwaters of mountain streams. Rapid

Occurs along a river and is characterized by turbulent water

Define the 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

Define the landforms associated with the headwaters of mountain streams. Lake

Occurs where water is impounded by some obstruction

Which of the following are considered to be causes for severe flooding events other than precipitation alone?

Rainfall coinciding with snowmelt and ice dams in a river Stalled hurricane Prolonged drought followed by intense precipitation Failure of a dam

Select all the natural causes for flooding from the list below.

Regional precipitation Local heavy precipitation Eruption of snow-covered volcano Snowmelt

From the list below, select the factors that control the deposition of a delta.

River and ocean ice Vegetation Wave action Discharge Sediment load

Select common features located along low-gradient rivers.

River terraces Single channels Meanders Floodplains

Which of the following are primary factors that influence a stream's profile?

Rock type Climate Sea level Tectonics

Select the two conditions that resulted in the 1993 upper Mississippi River flood.

Severe precipitation was caused by warm moist air from the Gulf of Mexico and cold Arctic air merging. The ground was already saturated from early spring rains.

Select consequences to a river when a dam is constructed.

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.

What is a drainage basin?

The naturally defined area that a stream drains

What is stream abrasion?

The process of grains chipping, scraping, and sandblasting the streambed as they move downstream

Match the river drainage pattern with the appropriate description of its geology. Dendritic drainage pattern

Treelike pattern develops on rocks with similar resistance to erosion.

What is the name of the subsidiary channels that join up with the main river channel?

Tributaries

Select the human-caused flooding events from the list of flood causes below.

Urbanization Dam failure

What is a flood?

Water overflows a stream's channel.

Do changes in tectonics, human development, and geology affect river systems?

Yes

When steep, narrow drainages enter broader, more gentle valleys and streams deposit the large sediments they are carrying, ________________ _______________ form.

alluvial, fans

The lowest level to which a river can erode is its ______.

base level

The area that a stream naturally drains is called a drainage _______________

basin

A stream in a mountainous area that is carved from bedrock is called a(n) ________________ stream.

bedrock

The process of meander formation begins when a difference in roughness on the ______ causes water to move faster on one side of the channel than on the other.

bottom

A stream that flows in a network of many interconnected rivulets around numerous bars is a(n) _________________ stream.

braided

Flat-bottomed valleys between mountains would be good places to look for ______ rivers or streams.

braided

This is a natural ___________

bridge or arch

As water flows, it accumulates in natural cracks, which eventually form ______ rather than spreading across the land.

channels

Besides sea level and rock type, the other two primary factors that influence a stream or river's profile are ___________________ and _________________ .

climate or weather, tectonics

The feature formed when a river deposits its sediment near its mouth is a(n) ______.

delta

The drainage pattern associated with areas where the rocks have the same resistance to erosion is a ___________________ pattern, whereas _______________________ drainage patterns are found on symmetrical mountains.

dendritic , radial

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

discharge

As meanders develop on a floodplain and either the base level drops or a tectonic event causes uplift, the meanders deepen and become __________________

entrenched or incised

Acting as major sculptors of Earth's surface, rivers and streams ____________________ the landscape, carry the materials, and later deposit the sediments.

erode

An event in which the amount of water flowing through a river channel overflows its banks is a(n) ______________

flood

Viscosity is the resistance to _________________ exhibited by fluids.

flow, movement, or motion

Rivers are dynamic systems driven by precipitation and ____________________ .

gravity

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

greatest amount

The origin of a river is _________________ called its , and the end of a river is called its _______________

headwaters or head, mouth

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

headwaters; mouth is

The ______ the velocity of a river, the ______ its capacity to carry sediment.

higher; larger

Many historic floods are associated with the large precipitation that accompanies a(n) ________________________ ; a good example is the storm named Mitch in 1998 that brought 78 inches of rain in some places in a few days.

hurricanes or typhoons

Meanders, floodplains, and river terraces are commonly found along -____________________ gradient rivers.

low

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

lowest or minimum

Braided rivers carry more volume and larger size ranges of sediment types than ____________________ rivers.

meandering

The discharge of a river is measured in cubic ______________ per second.

meters or feet

The size of sediments in braided rivers typically is ______ than that carried by meandering rivers.

more varied

A large opening that goes all the way through a narrow panel of rock is called a ______. A smaller, but similar opening is called a ______. These features may form in areas where a narrow panel of rocks, called a ______, has formed due to weathering controlled by joints on both sides.

natural arch; window; fin

A cutoff meander may develop into a(n) __________________ lake.

oxbow

A stream or river that flows all year is ______.

perennial

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

perennial, ephemeral or intermittent

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

point bar

Streams are systems driven by ______.

precipitation and gravity

When water flows chaotically through narrow channels or over large rocks and other debris that partially block the channel, _________________ are formed.

rapids

Changes in water or sediment supply, change in slope, or changes to base level elevation can begin or end the life of a(n) ____________

river, stream, or creek

The principal processes that sculpt Earth's landscape are erosion and deposition by ____________________.

rivers or streams

The higher the velocity of a flowing stream, the larger its capacity to carry _________________.

sediment

Construction of dams causes an interruption of river flow. River _________________ are deposited upstream of the dam, shortening the life of the reservoir.

sediments

The particle size transported by water that is in between clay and sand is _______________-

silt

The amount that a river or stream channel curves in a given length is called its _________________

sinuosity

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

terraces

The flat benches that are perched above a river or stream and that stair-step upward and outward from the active channel are ____________________

terraces

Sinuosity refers to ______.

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

Waterfalls, lakes, and large boulders are landforms that characterize ______.

the headwaters of mountain streams

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

tributaries

When the gradient of a stream steepens or the channel is constricted by bedrock or obstacles, the flow of water becomes ______ forming ______.

turbulent; rapids

The property of a fluid that is defined as the resistance to flow is __________________

viscosity

An important and widespread geologic agent in eroding, transporting, and depositing sediment is flowing ____________________

water or H2O

Changes in the ______ can begin or end the life of a river.

water or sediment supply at the source slope the river flows across elevation at the base level