Deck 17: Streams and Floods: the Geology of Running Water

Question 1

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

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

Answer 1

D

Question 2

Which river has the greatest discharge of any stream on the Earth?

A) Nile
B) Mississippi
C) Congo
D) Amazon

Answer 2

D

Question 3

The deepest part of a curved stream channel,where the flow is fastest,is called the ________.

A) base level
B) point bar
C) stream gradient
D) thalweg

Answer 3

D

Question 4

In a region with prominent orthogonal sets of joints,a ________ drainage network is expected.

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

Question 5

Which type of drainage network is associated with badlands topography?

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

Question 6

The primary stream fed by tributaries within a dendritic drainage network is termed a ________ stream.

A) lead
B) trunk
C) taproot
D) pirate

Question 7

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

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

Question 8

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 9

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

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

Question 10

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 11

Runoff is NOT commonly derived from ________.

A) sheetwash
B) rainfall or snowfall
C) ocean currents
D) groundwater springs

Question 12

Along a large cone-shaped volcano,a ________ drainage network is expected.

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

Question 13

The region below a streambed where groundwater flows in the same direction as the stream but at a slower rate is termed the ________ zone.

A) low flow
B) vadose
C) water table
D) hyporheic

Question 14

Water in a stream flows from its _________ to its __________.

A) mouth,headwaters
B) mouth,source
C) source,headwaters
D) headwaters,mouth

Question 15

In a region characterized by a parallel series of ridges and valleys,a ________ drainage network is expected.

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

Question 16

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

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

Question 17

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

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

Question 18

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 19

A stream is ________.

A) flowing water confined to a channel
B) a small river found near its headwaters
C) a small river near the mouth
D) a large river near its source

Question 20

Along a uniform and steep slope of relatively weak substrate,a ________ drainage network is expected.

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

Question 21

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 22

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 23

Ultimately,the base level of a stream valley cannot be lower than ________.

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

Question 24

A "bird's foot" delta configuration,similar to that of the Mississippi River delta,forms when the ________.

A) oceanic current exceeds the river current
B) oceanic current is so strong that all sediment is removed as it arrives
C) river and oceanic currents are equal
D) river current exceeds the oceanic current

Question 25

In some cases,the push of flowing water can break chunks of solid rock off of the channel bed.These pieces are then carried along by a stream as _________

A) suspended load
B) dissolved load
C) bedload
D) discharge

Question 26

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 27

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 28

The lowest elevation to which a stream can downcut is the ________.

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

Question 29

V-shaped stream valleys result from the downcutting of stream erosion and ________.

A) mass wasting on the valley sides
B) isostatic rebound
C) the topographic rule of V's
D) conservation of angular momentum

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 shape of a delta is primarily determined by ________.

A) the shape of the river channel near the mouth
B) the average grain size of the suspended and bed loads
C) whether river currents or ocean currents are locally predominant
D) the type of rock that is weathering at the outcrop near the headwaters of the river

Question 32

The figure below shows two hypothetical streams that have identical cross-sectional areas but different channel shapes.Assuming all other factors are equal,stream ________ will have the fastest flow because of the difference in ________.

A) A; width
B) A; wetted perimeter
C) B; width
D) B; wetted perimeter

Question 33

The capacity of a stream depends on its __________.

A) discharge only
B) velocity only
C) bed load and velocity
D) competence and discharge

Question 34

A stream carrying sediment flows over the solid rock of its channel,polishing the rock and wearing it away.This is an example of __________.

A) scouring
B) abrasion
C) dissolution
D) saltation

Question 35

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 36

Running water dissolves soluble minerals.This material is most likely to be transported by a stream as _________.

A) suspended load
B) dissolved load
C) bedload
D) discharge

Question 37

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

A) be unchanged
B) become unpredictable
C) fall
D) rise

Question 38

All else being equal,water will flow faster in a stream with ________ and a ________ wetted perimeter.

A) well-developed meanders; small
B) well-developed meanders; large
C) a straight channel; small
D) a straight channel; large

Question 39

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 40

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

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

Question 41

Which of the following scenarios is more likely to cause a flash flood than a slow-onset flood?

A) the melting of snowpack in the spring time,coupled with rain
B) sustained rains during a distinct wet season
C) the failure of a stream channel's levees
D) the sustained presence of a storm over a region

Question 42

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 43

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

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

Question 44

Contrast the gradient of a typical stream at its headwaters versus its mouth.Sketch the longitudinal profile of this stream.

Question 45

Runoff from farm fields entering a stream system is likely to be __________ than that from naturally vegetated fields.

A) greater and more sediment-laden
B) smaller but more sediment-laden
C) greater but less sediment-laden
D) smaller and less sediment-laden

Question 46

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 47

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 48

Differentiate between dissolved load,suspended load,and bed load.

Question 49

Which of the following is MOST likely to result in stream rejuvenation?

A) the discharge of a stream decreases
B) the base level of a stream drops
C) the land surface beneath a stream subsides
D) a drainage reversal occurs

Question 50

Using the image below label the stream channel,meander,floodplain,headwaters,and mouth.Additionally,sketch a cross-section of this stream from A to A' and from C to C'.

Question 51

First identify,then compare and contrast the features in the two photographs below.

Question 52

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

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

Question 53

Two 100-year floods can occur in two consecutive years.Use the concept of recurrence interval to explain how this is possible.

Question 54

Contrast the drainage patterns in the illustrations below.Why do they differ in appearance?

Question 55

Urbanization of a watershed is most likely to result in __________.

A) increased infiltration of rainwater
B) a longer lag time between storms and the onset of flooding
C) an increase in the volume of water entering streams after rainfall
D) a decrease in the likelihood of flash flooding

Question 56

Geologists are trying to determine the discharge of a river.The stream is semicircular in shape with a width of 10 m.They measure the velocity of the river to be 0.2 m/s.What is the discharge of the river? Sketch this cross section,and show your work.

Question 57

Which of the following is NOT true? 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 58

What is a flash flood? Suggest two circumstances that might lead to flash flooding.

Question 59

The hydrograph below shows the discharge of a stream in a natural system following a rainfall event.Draw a similar graph showing how the discharge curve might change following urbanization of this same system.Why has this change taken place?

Question 60

Sketch a meandering stream in map view.Your drawing should include (labeled)the channel,floodplain,meanders,and at least one oxbow lake.How does an oxbow lake form?