Deck 14: Streams and Floods: The Geology of Running Water

Question 1

The total sediment load of a stream consists of all of the following EXCEPT the ________ load.

A)turbulent
B)suspended
C)bed
D)dissolved

Answer 1

A

Question 2

Landslides along cut banks are common;how would a landslide along a cut bank affect the discharge of a river (hint: the equation for discharge is D = Ac x Vₐ)?

A)The discharge would decrease because the velocity of the river would increase.
B)The discharge would increase because the velocity of the river would decrease.
C)The discharge would increase because the cross-sectional area of the river would decrease.
D)The discharge would increase because the cross-sectional area of the river would increase.

Answer 2

D

Question 3

The figure below shows an example of a ________ drainage network.

A)dendritic
B)radial
C)rectangular
D)trellis

Answer 3

B

Question 4

The slope of a stream surface measured between two points along its course is the ________.

A)base level
B)floodplain
C)gradient
D)thalweg

Question 5

The figure below shows an example of a ________ drainage network.

A)dendritic
B)radial
C)rectangular
D)trellis

Question 6

In a region with prominent orthogonal (perpendicular to each other)sets of joints,a ________ drainage network is expected.

A)dendritic
B)radial
C)rectangular
D)trellis

Question 7

The outer edge of a meander,where material is being eroded,is called a(n)________.

A)meander neck
B)cut bank
C)point bar
D)abandoned meander

Question 8

The inner edge of a meander,where sediment is deposited,is called a(n)________.

A)meander neck
B)cut bank
C)point bar
D)abandoned meander

Question 9

Meandering streams ________.

A)consist of a series of intertwined channels that are overloaded with sediment
B)have flowing water either episodically or during only a portion of the year
C)have a channel that is highly sinuous (curvy)
D)are those that divert flow from streams they have intersected through stream erosion

Question 10

The figure below shows an example of a ________ drainage network.

A)dendritic
B)radial
C)rectangular
D)trellis

Question 11

Ephemeral streams ________.

A)consist of a series of intertwined channels that are overloaded with sediment
B)have flowing water either episodically or during only a portion of the year
C)have a channel that is highly sinuous (curvy)
D)are those that divert flow from streams they have intersected through stream erosion

Question 12

As the velocity of flow decreases,which of the following is NOT true?

A)The flow tends to become more laminar.
B)The competence increases.
C)Suspended sediment starts to be deposited.
D)The saltation of the bed load may cease.

Question 13

The discharge of a river will increase if ________.

A)the water in the river slows down
B)it rains in the drainage basin area
C)the area does not receive rain for a while
D)sediments settle to the bottom of the river

Question 14

Braided streams ________.

A)consist of a series of intertwined channels that are overloaded with sediment
B)have flowing water either episodically or during only a portion of the year
C)have a channel that is highly sinuous (curvy)
D)are those that divert flow from streams they have intersected through stream capture

Question 15

Within a meander,where is sediment most likely to be deposited?

A)on the outer banks of the meander
B)on the inner banks of the meander
C)uniformly to either side of the meander
D)directly in the middle of the meander

Question 16

A small mountain stream will have a ________ competence and a ________ capacity than the Mississippi River.

A)lower;lower
B)lower;greater
C)greater;greater
D)greater;lower

Question 17

The discharge of a river traveling through a temperate region will typically ________ downstream;the discharge of a river traveling through an arid region will typically ________ downstream.

A)increase;increase
B)decrease;decrease
C)increase;decrease
D)decrease;increase

Question 18

Ultimately,the base level of a stream valley can be no lower than the ________.

A)average elevation of the continent on which it is found
B)average elevation of the sea
C)average elevation of the local catchment
D)maximum elevation of the local catchment

Question 19

In uniform sediments with a relatively constant and gentle slope at the surface,a ________ drainage network is expected.

A)dendritic
B)radial
C)rectangular
D)trellis

Question 20

Which of the following is true of ephemeral streams but NOT permanent streams?

A)They are subject to erosion of sediment.
B)They contain water only during rainfall.
C)They can be fed by large drainage basins.
D)They occur only in tropical regions.

Question 21

The competence of a mountain river is ________ than that of a river on a floodplain because ________.

A)lower;the gradient is greater
B)higher;the gradient is greater
C)lower;there are more boulders
D)higher;there is more water

Question 22

A meander that is cut off to become completely isolated from the main channel but which retains water is a(n)________.

A)meander neck
B)cut bank
C)oxbow lake
D)thalweg

Question 23

The flat-lying area surrounding a river channel is termed the ________.

A)base level
B)floodplain
C)stream gradient
D)thalweg

Question 24

Why do meandering rivers meander (move)across their floodplain?

A)because the large amounts of sediments that choke the rivers create point bars that are easily eroded away by additional flow of the rivers
B)because they carry very small amounts of sediment and thus are not slowed down as a result of friction between the sediment and the river bottom
C)because they are curved,which causes erosion on one side of the curve and deposition on the other side of the curve,thus moving the river in the direction of erosion
D)because sediment is constantly being deposited on the river bottom,which causes the river to overflow its banks and create a new channel

Question 25

All else being equal,water will flow faster in a stream that has a ________,which is typically found near the river's ________.

A)steep gradient;source
B)steep gradient;mouth
C)gentle gradient;source
D)gentle gradient;mouth

Question 26

The base level of a tributary would become ________ if a dam and a reservoir were constructed where it flowed into a trunk stream.

A)lower
B)slower
C)faster
D)higher

Question 27

At a river delta,which of the following is FALSE?

A)The stream gradient decreases.
B)A single channel breaks into multiple,radiating distributary channels.
C)The competence decreases.
D)The stream channel becomes very straight because of the large sediment load.

Question 28

Geological evidence suggests that many millions of years ago,the Amazon basin drained toward the west rather than the east.What caused this drainage reversal?

A)a rise in the global sea level
B)a lowering in the global sea level
C)the rise of the Andes Mountains
D)global climate change

Question 29

Using the following graph,predict the discharge for a 100-year flood.

A)600 ft³/s
B)650 ft³/s
C)700 ft³/s
D)100 ft³/s

Question 30

What physical property of the underlying rock would lead to the formation of a cliff over which a waterfall may form?

A)a high resistance to erosion
B)high porosity
C)large permeability
D)very fine grain sizes

Question 31

The stream gradient of most rivers ________.

A)is greater near the source than near the mouth
B)is greater near the mouth than near the source
C)does not change significantly as a river flows downstream
D)is greater for a meandering stream than for any other type

Question 32

The ________ is the average number of years between floods.

A)discharge limit
B)annual probability
C)recurrence interval
D)flood-hazard gap

Question 33

When one stream captures the flow from another stream it is called ________.

A)stream rejuvenation
B)stream piracy
C)antecedent capture
D)beveled capture

Question 34

The figure below is an aerial photograph of a meandering stream.The light-colored features labeled with arrows are ________.

A)thalwegs
B)cut banks
C)flood plains
D)point bars

Question 35

Pirate streams ________.

A)consist of a series of intertwined channels that are overloaded with sediment
B)have flowing water either episodically or during only a portion of the year
C)have a channel that is highly sinuous (curvy)
D)form when headward erosion causes one stream to intersect another

Question 36

________ increases the volume of water in and decreases the lag time of a flood.

A)Establishment of natural levees
B)Urbanization of an area
C)Building a floodway
D)Establishing farms

Question 37

One way to mitigate flooding is to build ________,which are areas that are intended to flood and as such are not zoned for buildings.

A)floodways
B)floodplains
C)peneplains
D)artificial levees

Question 38

Which of the following is FALSE? A 100-year flood ________.

A)has a 1% chance of occurring in any given year
B)is more destructive than a 50-year flood
C)cannot occur in successive years
D)is based on the average recurrence interval of past floods for a particular stream

Question 39

A(n)________ is formed when a meander neck is cut off from the rest of the river.

A)oxbow lake
B)cut bank
C)point bar
D)floodplain

Question 40

The distinction between a valley and a canyon is ________.

A)nonexistent;the two terms are synonymous
B)that the sides of a canyon are more steep than those of a valley
C)that the sides of a valley are more steep than those of a canyon
D)that valleys are often cut by streams,whereas canyons are eroded by the wind

Question 41

If a 50-year flood occurs on the Mississippi River this year,what is the probability that a flood of the same magnitude will occur in the following year?

A)zero
B)1%
C)2%
D)50%

Question 42

If a dam is built on a river,what effects might be felt downstream?

A)increase in the fish population
B)decrease in sediment supply
C)increase in the sediment load
D)increase in flood potential

Question 43

Building dams on rivers traps sediment behind the dams-sediments that would normally have traveled all the way down the river and out into the ocean.How might this sediment starvation affect the coastal beaches?

Question 44

________ release extra sediment to rivers,while ________ cause(s)a decrease in the sediment supply downriver.

A)Dams;urbanization
B)Farms;urbanization
C)Dams;farms
D)Farms;dams

Question 45

Name and describe two methods to mitigate flood hazards.

Question 46

Urbanization causes an increase in the volume of water entering a stream due to the abundance of ________ surfaces in cities and towns.

A)permeable
B)impermeable
C)pourous
D)potable

Question 47

You are a geologist trying to determine the discharge of a River.The stream is semi-circular in shape with a width of 10 meters.You measure the velocity of the river to be 0.2 m/s.What is the discharge of the river? Make sure to show your work for full credit.

Question 48

________ provide hydroelectric power;however,they also form barriers for migrating fish.

A)Dams
B)Levees
C)Floodways
D)Floodplains

Question 49

What is a stream? How is it similar/different from a river or a creek?

Question 50

Dead zones occur due to a lack of ________ in the oceans.

A)sediments
B)phosphorus
C)oxygen
D)nitrogen

Question 51

Dead zones are areas along the coasts where rivers spill excess nutrients into the oceans.Microorganisms feed on these nutrients,which in turn causes them to use up all the ________ in the water and kill larger organisms like fish.

A)sediments
B)phosphorus
C)oxygen
D)nitrogen

Question 52

What is the effect on a river that runs through farmland?

A)Sediment load will increase.
B)Sediment load will decrease.
C)The farm will dry out the river.
D)The farm will add water to the river.

Question 53

If a large airport,complete with paved runways,parking lots,and many new structures,is built next to a river,what might the effect be?

A)a decrease in the fish population
B)diminished nutrient supply for fish
C)an increase in the likelihood of flooding
D)Overuse of water will dry out the river.

Question 54

What will happen to a stream if the local base level is increased,for instance,by adding a dam to the river?

Question 55

Why are artificial levees only useful for some flooding events?

A)Levees cannot be built larger than the surrounding floodplain.
B)Flash floods occur too quickly for officials to close the levees.
C)Levees are built in rural areas and will not help for flooding in the city.
D)Large floods can create high pressures and undermine the levee.