Deck 6: Streams and Flooding

Question 1

The total amount of material transported by the stream is called

A) Capacity.
B) Strength.
C) Volume.
D) Load.

Answer 1

D

Question 2

A stream's load consists of

A) The amount of water it carries over a specified time period.
B) The amount of material (solid and dissolved) carried by the water in a stream.
C) The amount of water and solid material carried downstream.
D) The amount by which a delta increases in size in a year.

Answer 2

B

Question 3

What develops a pattern of many complex channels that divide and rejoin and when the sediment load is considerably larger in relationship to the volume of water?

A) Oxbow lake
B) Meander
C) Braided stream
D) Floodplain

Answer 3

C

Question 4

When a stream bends or curves what begins to form

A) Point bars.
B) Cut banks.
C) Meanders.
D) Oxbow lakes.

Question 5

If the width of the stream is 20 feet,the depth 5 feet,and velocity 10 feet per second,then the discharge is

A) 1000 feet/second.
B) 1000 square feet/second.
C) 1000 cubic feet per second.
D) None of the answers are correct.

Question 6

A depositional feature formed when a fast-flowing stream joins a slower one or a mountain stream flows out into a plain is

A) An oxbow.
B) A meander.
C) A floodplain.
D) An alluvial fan.

Question 7

A stream generates its own floodplain by

A) Erosion during meander migration.
B) Sediment deposition during meander migration.
C) Sediment deposition during flooding.
D) All of the choices are correct.

Question 8

Streams draw their water from a region known as the

A) Drainage divide.
B) Drainage lake.
C) Drainage aquifer.
D) Drainage basin.

Question 9

A drainage basin

A) Includes the area from which surface water flows into a stream segment.
B) For a river includes all the drainage basins for that river's tributaries.
C) Increases in size and proportion to the size of the stream or river it feeds, for the same climate.
D) All of the choices are correct.

Question 10

The volume of water flowing past a point along a stream in a given period of time is the stream's

A) Drainage basin.
B) Discharge.
C) Load.
D) Capacity.

Question 11

A hydrograph is:

A) A plot of stream stage or discharge versus time
B) A map showing the extent of a floodplain
C) A diagram that illustrates flood recurrence intervals
D) A graph of variations in precipitation through time

Question 12

A flood crest

A) Usually increases downstream from the area covered by the rain storm.
B) Is the maximum stage of the river at any point along the stream from a flood event.
C) Can take years to travel from its initiation point to the mouth of a river.
D) Is when a stream overflows its normal flow channel and spills out onto the floodplain.

Question 13

The principal source of evaporated water that becomes precipitation are

A) Streams.
B) Glacier ice.
C) The oceans.
D) Volcanic eruptions.

Question 14

The suspended load of a stream consists of

A) Fine sediment carried in suspension.
B) Material rolled along the streambed.
C) Dissolved material in solution.
D) Sediment trapped in a reservoir behind a dam.

Question 15

The steepness or slope of a stream channel in the direction of flow is the channel's

A) Capacity.
B) Bed load.
C) Base level.
D) Gradient.

Question 16

A cut-off meander is also known as

A) A drainage basin.
B) An oxbow.
C) A floodplain.
D) A delta.

Question 17

A fan-shaped pile of sediment deposited at a stream's mouth is a

A) Delta.
B)
B) Alluvial fan.
C) Discharge.
D) A or

Question 18

On the inside bank of a meander,where water flow slowly,__________ may be deposited.

A) A delta
B) An oxbow
C) A point bar
D) An alluvial fan

Question 19

All other factors being equal,the risk of stream flooding is probably greatest

A) In an area of high rainfall evenly distributed through the year.
B) In a very cold climate where snow rarely melts.
C) In an area that receives its rain mostly in a few intense storms.
D) In an area that receives little rain.

Question 20

Below ground,water moves through soils and rocks by a process known as

A) Infiltration.
B) Percolation.
C) Seepage.
D) Discharge.

Question 21

Channelization strategies include all of the following except

A) Dredging and deepening a channel.
B) Straightening a channel.
C) Building a flood-control dam.
D) Deliberately cutting off a meander.

Question 22

A basin designed to hold surplus surface runoff,keeping it out of a stream is

A) A retention pond.
B) A drainage basin.
C) A delta.
D) An oxbow lake.

Question 23

A stream's base level is the lowest level to which it can cut down or erode its channel.

Question 24

Once formed,meanders enlarge downward only,cutting deeper and deeper over time.

Question 25

When a stream carrying suspended sediment enters a reservoir,

A) It deposits its suspended sediment load.
B) Scouring by the suspended sediment carves the reservoir deeper.
C) The sediment stays suspended in the reservoir water and pollutes it.
D) The suspended sediment stays in suspension and is released below the dam, polluting water downstream.

Question 26

Strategies designed to reduce damage to structures in floodplains include

A) Planting vegetation within the stream channel.
B) Filling in land in the floodplain to reduce flood volume.
C) Raising buildings on stilts to elevate floor levels.
D) All of the choices are correct.

Question 27

A flood stage is reached when the stream stage supersedes the

A) Bank width.
B) Bank length.
C) Bank height.
D) Bank stage.

Question 28

Hazards regarding floods can be greatly reduced where open lands are available by using

A) Slope stabilization.
B) Rock bolts.
C) Channelization.
D) Retention ponds.

Question 29

Saltation is a process by which streams dissolve soluble minerals and become saltier.

Question 30

A cut bank is the outside bank of a meander that is subject to erosion.

Question 31

Urbanization in a floodplain

A) Does not occur because it would be unsafe.
B) Reduces flood hazards by preventing infiltration.
C) Has no effect on flood hazards.
D) Increases flood hazards by reducing floodplain storage capacity and increasing surface runoff.

Question 32

Tile drainage systems and city storm sewers

A) Reduce flood hazards by removing water quickly.
B) Have no effect on flood hazards; they do not drain into streams.
C) Increase flood hazards by preventing infiltration.
D) Reduce flooding where they are installed but may increase it along a stream into which the discharge flows.

Question 33

A dam breaks and stream stage is being monitored just below the dam and several kilometers downstream.Which of the following is true?

A) The upstream hydrograph will show a lower, broader peak.
B) The flood will produce identically shaped peaks on the hydrographs at both places.
C) The downstream hydrograph will show a lower, broader peak.
D) Overall stream discharge will be unaffected; hydrographs will show no changes.

Question 34

Highly porous and permeable soils would reduce flooding.

Question 35

Stream-deposited sediments are often well sorted because the size of particles moved is a function of stream velocity,quantity of water,and discharge.

Question 36

Artificial levees built along a stream

A) Effectively stop all flooding, as along the Mississippi River.
B) May, if breached, trap floodwaters behind them.
C) Reduce stream stages by moving water faster.
D) All of the choices are correct.

Question 37

An increase in sedimentation along a stream can be caused by

A) A recent forest fire.
B) A beaver dam.
C) Fish spawning.
D) Animal migration.

Question 38

Suitable uses for floodplain land include all of the following except

A) Grazing land for livestock.
B) A municipal sewage treatment plant.
C) A municipal park.
D) A golf course.

Question 39

The U.S.Geological Survey and the National Weather Service work together to

A) Alert the public about impending flash flooding by using drainage basin characteristics (USGS) and meteorological events (NWS) to predict areas and timing where rapid water level rise may occur.
B) Judge the amount of sedimentation that will fill a river channel in a year and thus help in flood forecasting.
C) Keep public officials informed about the narrowing or widening of the 100-year floodplain in upstream drainage basins.
D) Inform insurance companies that provide flood insurance to individuals about locations where flooding is most probable.

Question 40

A region has just had a 100-year flood.That means that

A) A flood event of that size has a 1 percent probability of occurrence in the next year.
B) Another equally large flood will occur in one hundred years.
C) Another flood of that size cannot happen in the same year.
D) All of the choices are correct.

Question 41

When flood recurrence intervals are estimated from historic records,the estimated intervals depend strongly on the length of time represented by the records.

Question 42

The term "flood-frequency curve",though in common use,may be misleading in that it implies that floods of certain sizes recur at regular intervals.

Question 43

Most human activities tend to reduce flood hazards,so the frequency of floods of a given size has been decreasing for nearly all streams.

Question 44

Plants can reduce the risk of flooding by consuming water,keeping soil loose and permeable and slowing surface runoff.

Question 45

Maximum stage is used to describe the magnitude of the flood and when the maximum stage is reached the stream is said to trough.

Question 46

Use of dams to form reservoirs for water supply may conflict with the flood-control functions of the dam/reservoir system.

Question 47

Streams respond quickly to water input,so once a heavy rainstorm has stopped,floodwaters will rise no higher.

Question 48

Flash floods may be especially likely where runoff water is confined to a narrow valley.

Question 49

A flash flood is a variety of upstream flood.

Question 50

The height of the surface of the water is at any given point is indicated by the stage of the stream.

Question 51

The difference of time between a precipitation event and peak flood discharge is termed as peak lag time.

Question 52

Because upstream floods affect localized areas,they are more likely to be brief than are downstream floods.

Question 53

After disastrous natural floods in the Grand Canyon in 1942 and 1996,the Glen Canyon Dam was built to control those floods.

Question 54

Floods only occur where human activities tamper with natural stream systems.

Question 55

A diversion channel is used to shorten a stream and increase its gradient.

Question 56

Constructing levees may increase the amount of property at risk from future flooding by encouraging floodplain development.

Question 57

Infiltration of water below an artificial reservoir can induce earthquakes.

Question 58

Concern about floods is such that accurate flood-hazard maps are now available for all streams in the United States.

Question 59

Unlike streams,lakes do not flood because runoff does not drain into lakes.

Question 60

Only surface runoff reaches streams; subsurface water is stagnant and does not move.

Question 61

To minimize the disturbance to a stream spanned by a bridge,supports for the bridge should be founded within the stream and made as wide as possible.

Question 62

The Aswan High Dam in Egypt has resulted in diminished crop production in the Nile River floodplain downstream because annual flooding no longer brings new and fertile soil.

Question 63

The Glen Canyon Dam,built on the Colorado River between 1956 and 1966 forming Lake Powell is now considered by many to be an environmental liability.