Streams & Flooding (Chapter 13 Quiz)
Compared with curve 2 on this hydrograph, what is a possible explanation for curve 1?
-The basin for curve 1 has steeper slopes than the basin for curve 2. -The storm recorded by curve 1 was shorter and more intense than the storm represented by curve 2. -Curve 1 shows the same area as curve 2 but after urbanization.
This figure shows four numbered river terraces, with 1 being the highest and 4 being the lowest. Which is the oldest terrace?
1
If a stream drops 15 meters in 15 kilometers, what is its gradient?
1 meter per kilometer
If a river originates 200 meters above sea level and travels 100 kilometers to the ocean, what is the average gradient in meters per kilometer?
2 meters per kilometer
Using this plot of annual peak discharge, which of the following sizes of flood is most likely to be exceeded in any given year?
200 cubic meters per second
This figure shows four numbered river terraces, with 1 being the highest and 4 being the lowest. Which is the youngest terrace?
4
Which of the features on this aerial photograph is a point bar?
A
If erosion and deposition occur at the same rate, how can we best describe the particles of sediment on a streambed?
As the sediment moves downstream, it is replaced by a similar volume of sediment.
In the accompanying hydrograph for a major river, a flood was caused by a single episode of heavy rainfall 50 kilometers upstream. When did the rain most likely occur?
At time A
At which site along this stream would a point bar form?
B
Using this plot of annual peak discharge, what is the probability each year that a flood of 1,000 cubic meters per second will occur?
Between 10% and 20%
What type of stream is shown in this figure?
Braided stream
What type of stream is shown in this photograph?
Braided stream
Which of the features on this aerial photograph represents the former position of a meander?
C
In the diagram below, the most likely place where sediment will be deposited on the streambed is at
D (On/By concrete)
Which of the following is true about a delta?
Deltas form some layers that are horizontal and form some that are inclined toward the ocean.
What is the pattern of discharge shown by this hydrograph?
Discharge quickly increases and gradually decreases.
What units of measure would most likely be represented by letters A-E on the bottom of the accompanying hydrograph?
Hours
What could cause this stream to begin carving into the landscape? (Seas up)
If base level is lowered, such as a drop in sea level If the land is uplifted relative to the sea If a change in climate weathers and weakens the rocks
Which of the following is the most common cause of river and stream flooding?
Intense precipitation
Where do mountain streams get most of their load of sediment?
Landslides, slope failures, and erosion of the mountain sides
Which of the following typically decreases downstream in a river?
Maximum sediment grain size
What type of stream is shown in this figure?
Meandering stream
Which of the following features are generally not associated with mountain streams and rivers?
Meanders
Which of the following is true about the formation and migration of meanders?
Migration of meanders back and forth can help form a floodplain.
Which of the following is true about the base level of a stream?
Most streams have a lower gradient close to their base level.
What was the cause of flooding in the 1993 upper Mississippi River flood?
Persistent thunderstorms caused large amounts of rainfall over a several-state region.
Which of the following features can be formed by deposition along a low-gradient stream?
Point bar
Which of the following features is most related to erosion along a low-gradient stream?
Point bar Floodplain Levee None of these are correct.
How is an alluvial fan formed?
Sediment is deposited by debris flows and streams that decrease in velocity along the mountain front.
What does the associated graph indicate about a stream?
Silt and clay are carried in suspension under most stream velocities. Sand and gravel are deposited at low velocities but transported at higher velocities. Sand is carried in suspension only at high velocities. As fast-moving water slows down, fine sand can switch from transport by suspension to the bed load.
Which particles of sediment are most likely to be transported as suspended load?
Small, low density particles
Which of the following statements about streams is not true?
Streams typically do not respond to a change in climate.
What is the mostly likely setting for this drainage pattern?
The area has folded or faulted rocks with different resistances to erosion.
What could cause a canyon to be deeper upstream than downstream?
The area upstream could be uplifted more than areas downstream. The area upstream is higher above base level and so results in deep erosion. A steeper gradient allows more erosion upstream. All of these are correct.
What is a reasonable interpretation for the flow event recorded by this hydrograph?
The drainage basin has several distinct parts.
Which of the following influences whether a flood occurs?
The height of levees The amount of discharge Urbanization (replacing farms or natural land with buildings) The width of the channel
What can you conclude by comparing the left and right hydrographs, each of which depict the same amount of time?
The left diagram has a higher peak discharge.
Which of the following is true of a 100-year flood?
The probability of a 100-year flood occurring on any given year is 1:100.
What are some effects of building a dam?
The reservoir (lake) traps sediment that over time fills up part of the reservoir.
What is the mostly likely setting for this drainage pattern?
The rocks have a relatively equal resistance to erosion.
What happens to a river as it flows through a delta and encounters the sea?
The total sediment load carried by the river decreases.
Which of the following is the main reason that a delta forms when a stream flows into a lake or sea?
The velocity of the stream decreases.
What would happen if the amount of ice in this area increases?
The weight of the ice depresses the land, possibly causing the river to change direction.
Which of the following does not influence whether sediment is picked up by a stream?
Whether the stream flows north-south or east-west
On this graph of discharge versus season for a river in the Rocky Mountains, why is the highest runoff likely to be in the spring?
Winter snow melts in the spring.
Feature A, formed where the Nile River encounters the Mediterranean Sea, is
a delta.
When water in a stream or desert wash decreases in velocity, sediment that the stream carries can be deposited in
a delta. an alluvial fan. a floodplain.
Comparing these two curves on this hydrograph, the solid curve could record
a shorter but more intense precipitation event. the response of the stream to urbanization. a more rapid spring snowmelt.
Which of the following features is NOT formed by stream deposition?
a waterfall
Which of the following is NOT associated with braided streams?
cutoff meanders
The type of feature shown in this figure is
entrenched meanders.
Construction of a dam results in
increased erosion by clear water released from the dam.
In this diagram, water velocity downstream generally
increases.
Bedrock and sediment in a stream is most susceptible to erosion if it is
located in a turbulent part of the river.
Formation of entrenched meanders can result from a
low-gradient river followed by downcutting.
Which of the following can have a significant effect on a river?
rises and drops in sea level tectonics types of bedrock in the river changes in climate
The size of clasts that a stream can carry is primarily controlled by
the velocity and turbulence of the current.
What does a profile of a river from its headwaters to its mouth typically show?
A curved shape that flattens out downstream
Which of the following is a condition favoring deposition of sediment?
A decrease in gradient of the stream
Which of the following is unlikely to cause deposition of sediment along a stream?
A drop in sea level
Which of the following is true about levees?
A levee can trap water on the floodplain after the flood has subsided.
How did the entrenched meanders shown in this figure form?
A meandering river carved into the land due to uplift or falling base level.
Which of the following is true about how a stream erodes material?
Abrasion is concentrated on the upstream side of obstructions.
What is not true about terraces?
According to superposition, the lowest terrace is the oldest.
Which of the following is commonly associated with tributaries?
Rapids when the tributary joins the main river Delivery of sediment to the main river An increase in the discharge in the main river
What would happen if the ice in this area melted away?
Rivers could change direction and flow away from the area once covered by ice.
Which of the following accompanies urbanization (replacing farms and open areas with cities)?
Runoff occurs more quickly and produces a higher peak flow.
Which of the following is true about transport of sediment in a stream?
Sand can be transported in a series of bounces along the stream bed.