Question 1

Figure 16.20 
-Using Figure 16.20 in your textbook, which statement comparing stream patterns is true?

Accepted Answer

The braided pattern is characterized by a highly variable stream channel with numerous interconnected channels, whereas the meandering pattern has a single channel with pronounced curves. The braided pattern is less stable because flow is divided among multiple channels, and sediment is deposited on bars between channels, which can change rapidly in position and size. Meandering patterns tend to have coarser sediment grains because the slower flow allows sediment to settle out, while braided patterns have finer sediment because of the high flow velocities required to move the sediment.

Question 2

During a flood, which factor does not decrease further away from the channel during a flood?

Accepted Answer

The answer of During a flood, which factor does not...

Question 3

What is the recurrence interval that is considered acceptable by insurers for development on flood plains?

Accepted Answer

Insurers generally consider a 100-year recurrence interval as an acceptable level of risk for development on flood plains. This means that there is a 1% chance of a flood occurring each year that would cause damage equal to or greater than the level defined as a 100-year flood. Development in areas with higher recurrence intervals would be considered too risky for insurance purposes.

Question 4

What is the base level of a stream?

Accepted Answer

The base level of a stream is the elevation at which it enters a larger body of water, such as a lake or ocean. This elevation is determined by the elevation of the larger body of water and the slope of the stream.

Question 5

A smooth concave-up profile suggests that a river

Accepted Answer

A smooth, concave-up profile indicates that the river is well-adjusted to its sediment load and discharge, allowing for a steady, consistent flow. If the flow were too fast or too slow, it would result in a different profile. Meandering is also not indicated by a smooth profile, and changes in bedrock type would likely result in a more variable profile.

Question 6

A(n) ________ is formed on a floodplain when ground water seeps into a cutoff channel of a meandering river.

Accepted Answer

When a meandering river changes its course, it can leave behind a crescent-shaped body of water called an oxbow lake. This occurs when a cutoff channel is formed due to erosion and sediment deposition. Groundwater can seep into the cutoff channel, leading to the formation of a lake. Therefore, the correct term for this type of feature on a floodplain is an oxbow lake.

Question 7

To make the data fall into a line that can be analyzed for a 100-year flood, scientists use

Accepted Answer

Nonlinear axes are used to make the data fall into a line that can be analyzed for a 100-year flood, allowing for a more accurate representation and analysis of extreme events that do not fit well into linear scales.

Question 8

Which of the following is not a reason that grain size of sediment tends to decrease downstream?

Accepted Answer

Gravity is not a reason for the decrease in grain size downstream; rather, it is the force that causes sediment to move. Abrasion, decreasing shear force, and rounding contribute to the reduction in grain size as sediment is transported.

Question 9

The area where the flow is faster and deeper around the outside of a channel bend is called

Accepted Answer

Cutbanks occur on the outer edge of a meander bend where the water flows faster and deeper, eroding away the bank over time. Choice B) a meander refers to the bend in the channel itself. Choice C) a point bar is the opposite of a cutbank, forming on the inside of a meander bend where the water flow is slower and deposits sediment. Choice D) a braid refers to a channel with multiple, interconnected channels, not specific to bends in the channel.

Question 10

How are natural levees formed?

Accepted Answer

Natural levees are formed when suspended load (sediment) is deposited on the river banks during floods. As the water spreads over the floodplain, its velocity decreases, causing the sediment it carries to settle out and gradually build up the banks.

Question 11

You are walking along a stream and you find small, smooth grains and sediment, that is very well-sorted. What can you deduce from this observation?

Accepted Answer

The small, smooth grains and well-sorted nature of the sediment suggest that it has traveled a long distance, allowing for the sorting and smoothing processes to occur. The slow stopping of the water indicates a gradual deposition, which is consistent with the well-sorted characteristic of the sediment.

Question 12

Which appears to be the best method of living near floodplains?

Accepted Answer

Effective land use planning can involve avoiding building in areas that are prone to flooding or building infrastructure that can withstand floods. This approach can reduce the risk of damage to property and loss of life. While sandbags and flood-proofing buildings can help, they are often only temporary solutions and may not be enough in the face of severe flooding. Avoiding living near floodplains altogether, as option D suggests, may not be feasible or desirable for everyone. Effective land use planning can balance the benefits of living near water with the risks, creating safer and more sustainable communities.

Question 13

Where does a point bar accumulate?

Accepted Answer

A point bar is an accumulation of sediment on the inside of a meander where slow-moving water deposits sediment.

Question 14

In terms of the 100-year flood area, estimates of water depth calculations generated by computer models are uncertain. Evaluate the impact of this fact on insurers of landowners residing near that area.

Accepted Answer

The uncertainty in water depth calculations generated by computer models can lead to differences in depth, which may cover a large area of land near the 100-year flood area. As a result, insurers may need to investigate further and evaluate the potential impact of this uncertainty on landowners residing near that area.

Question 15

In a channel, where is flow velocity the fastest?

Accepted Answer

Flow velocity is fastest near the outside bank of a meander because that's where the channel is deepest and the flow has the most energy. It slows down near the inside of a meander and in the middle of a curve where the channel is shallower.

Question 16

________ would not increase the intensity of a flash flood.

Accepted Answer

A broad alluvial fan would not increase the intensity of a flash flood because it allows for the dispersion and absorption of water over a wide, flat area, reducing the speed and intensity of the water flow. In contrast, steep slopes, paved ground, and narrow bedrock canyons all contribute to faster runoff and higher water speeds, which can increase the intensity of flash floods.

Question 17

A student in the field is taking observational notes about a stream and postulates, "This stream must be shallower and slower downstream." Evaluate this statement.

Accepted Answer

The statement is probably false because discharge always increases as streams proceed downstream. While this might not be true in all cases, it is generally true for most streams. Additionally, the statement is not necessarily related to the depth or speed of the stream.

Question 18

What increases the severity of a prolonged flood?

Accepted Answer

Increased saturation of the ground can lead to increased severity of a prolonged flood as it means the ground cannot absorb any more water, causing it to accumulate and worsen the flooding. Options A, B, and D do not necessarily increase the severity of a prolonged flood.

Question 19

Figure 16.28 
-Using Figure 16.28 in your textbook, a flood level that occurred five times in 50 years is known as

Accepted Answer

A flood level that occurred five times in 50 years has a recurrence interval of 50 years divided by 5 events, which equals 10 years, making it a 10-year flood.

Question 20

Which is not an effect resulting from dam construction on a river?

Accepted Answer

Dam construction typically causes sedimentation to accumulate upstream of the dam and channel bed erosion downstream of the dam. Bank stabilization can also occur downstream of the dam. However, increased sediment build-up below the dam is not a common effect of dam construction.

Quiz 16: Streams: Flowing Water Shapes the Landscape

Figure 16.20 -Using Figure 16.20 in your textbook, which statement comparing stream patterns is true?