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The frequency of flooding onto floodplainsthe lands situated adjacent
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04 Jun 2020, 09:00
04 Jun 2020, 09:00
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The frequency of flooding onto floodplains—the lands situated adjacent to rivers and other waterways—depends on factors such as climate, drainage area, channel slope, and the absorptive capacity of soil. In rainy regions, the floodplain may be inundated frequently, and in arid regions the floodplain may remain dry for years. In many regions, floods occur primarily during the snowmelt runoff season.
Floods are often described in terms of their statistical frequency. A 100-year flood, for example, describes the level of floodwater expected to be equaled or exceeded once every 100 years. Such a flood is also considered the 1% annual exceedance probability flood (i.e., a flood with a 1% chance of being equaled or exceeded in any given year). Hydrologists commonly map the boundaries of 100-year floods to advise public officials on flood risk management and containment strategies.
Floods are often described in terms of their statistical frequency. A 100-year flood, for example, describes the level of floodwater expected to be equaled or exceeded once every 100 years. Such a flood is also considered the 1% annual exceedance probability flood (i.e., a flood with a 1% chance of being equaled or exceeded in any given year). Hydrologists commonly map the boundaries of 100-year floods to advise public officials on flood risk management and containment strategies.
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Difficulty:
65%
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Question Stats:
50% (03:43) correct
50%
(03:43)
wrong
based on 517
sessions
1. Which one of the following can be most logically inferred from the information given?
| The drainage area and channel slope of a waterway are positively correlated. | |
| The channel slope of a waterway is positively correlated with the area of the 100-year floodplain boundary. | |
| A 5-year flood has a 20% annual exceedance probability. | |
| The larger a waterway’s drainage area, the more frequently its floodplain becomes inundated. | |
| The greater the average channel slope of a waterway, the more prone the waterway is to snowmelt flooding. |
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Official Answer
A 5-year flood has a 20% annual exceedance probability.
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Difficulty:
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Question Stats:
52% (00:45) correct
48%
(00:41)
wrong
based on 526
sessions
2. For each of the following, select Yes if it is explicitly mentioned in the passage (Discussion) but not in the table. Otherwise select No.
| Yes | No | |
| Snowmelt flooding | ||
| Absorptive capacity of soil | ||
| Drainage area |
ShowHide Answer
Official Answer
Snowmelt flooding: No
Absorptive capacity of soil: Yes
Drainage area: No
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Difficulty:
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Question Stats:
56% (01:35) correct
44%
(01:46)
wrong
based on 449
sessions
3. For each of the following statements, select Yes if the information provided indicates that the statement is true. Otherwise select No.
| Yes | No | |
| A 100-year flood on the Jackson River would directly affect more people than would such a flood on the Porter River. | ||
| In Region X, Evans Creek drains into Jackson River. | ||
| The area representing the 1% annual exceedance probability for Deer Creek is 17 sq km. |
ShowHide Answer
Official Answer
A 100-year flood on the Jackson River would directly affect more people than would such a flood on the Porter River.: No
In Region X, Evans Creek drains into Jackson River.: No
The area representing the 1% annual exceedance probability for Deer Creek is 17 sq km.: Yes
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Re: The frequency of flooding onto floodplainsthe lands situated adjacent
[#permalink]
Updated on: 04 Jun 2020, 09:26
Updated on: 04 Jun 2020, 09:26
2
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A-No,since drainage area decreases but channel slope both Increases and decreases,no positive correlation.
B-No, because when channel slope Increases the area of the 100-year floodplain boundary both Increases and decreases,no positive correlation.
C-100 year flood has 1% annual exceedance probability,so a 5 year flood has more frequency so it's probability of occurrence will also be more ,here 100 year flood =20*5 year flood , meaning 20*1% probability of occurrence=20% annual exceedance probability
D-No it is not sure because the inundation depends on various other cases such as season,climate, absorptive capacity of soil,channel slope.
E-Flooding occurs due to snowmelt runoff season but there is no dependency directly show
2) Snowmelt flooding and drainage area are both shown in Discussion and in the table and only absorptive capacity of soil is only shown in Discussion
3)a)No,since it is not known that how many people live near Jackson or porter river
b)No,Evans creek and Jackson river data is shown independently.
C)Yes, beacuse for Deer creek the flood plain boundary is 17 sq km and 1% annual exceedance probability is in flood plain boundary area
B-No, because when channel slope Increases the area of the 100-year floodplain boundary both Increases and decreases,no positive correlation.
C-100 year flood has 1% annual exceedance probability,so a 5 year flood has more frequency so it's probability of occurrence will also be more ,here 100 year flood =20*5 year flood , meaning 20*1% probability of occurrence=20% annual exceedance probability
D-No it is not sure because the inundation depends on various other cases such as season,climate, absorptive capacity of soil,channel slope.
E-Flooding occurs due to snowmelt runoff season but there is no dependency directly show
2) Snowmelt flooding and drainage area are both shown in Discussion and in the table and only absorptive capacity of soil is only shown in Discussion
3)a)No,since it is not known that how many people live near Jackson or porter river
b)No,Evans creek and Jackson river data is shown independently.
C)Yes, beacuse for Deer creek the flood plain boundary is 17 sq km and 1% annual exceedance probability is in flood plain boundary area
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Re: The frequency of flooding onto floodplainsthe lands situated adjacent
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14 Apr 2021, 06:26
14 Apr 2021, 06:26
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Expert Reply
Official Explanation
1. Which one of the following can be most logically inferred from the information given?
Explanation
According to the table, Bear Run Creek has the least drainage area (2.3 square kilometers) and the greatest average channel slope (12.7 meters per kilometer), so drainage area and average channel slope are not positively correlated (ruling out A). Likewise, Bear Run Creek has the greatest average channel slope (12.7 meters per kilometer) but the second-to-least 100-year floodplain boundary area (1.8 square kilometers), so average channel slope and 100-year floodplain boundary are not positively correlated (ruling out B). Although the passage indicates that drainage area is a factor in the frequency of flooding onto floodplains, it does not suggest that a larger drainage area leads to more frequent flooding (ruling out D). Again, Bear Run Creek has the greatest average channel slope (12.7 meters per kilometer), but there are two other waterways in the table (Jackson River and Evans Creek) with a greater percentage of their floods that are snowmelt floods, showing that average channel slope and likelihood of snowmelt flooding are not positively correlated (ruling out E). The passage indicates that a 100-year flood level is expected to be equaled or exceeded once every 100 years. It follows logically that a 5-year flood is expected to be equaled or exceeded once every 5 years, making its annual exceedance probability 20% (C).
The correct answer is A 5-year flood has a 20% annual exceedance probability.
Explanation
According to the table, Bear Run Creek has the least drainage area (2.3 square kilometers) and the greatest average channel slope (12.7 meters per kilometer), so drainage area and average channel slope are not positively correlated (ruling out A). Likewise, Bear Run Creek has the greatest average channel slope (12.7 meters per kilometer) but the second-to-least 100-year floodplain boundary area (1.8 square kilometers), so average channel slope and 100-year floodplain boundary are not positively correlated (ruling out B). Although the passage indicates that drainage area is a factor in the frequency of flooding onto floodplains, it does not suggest that a larger drainage area leads to more frequent flooding (ruling out D). Again, Bear Run Creek has the greatest average channel slope (12.7 meters per kilometer), but there are two other waterways in the table (Jackson River and Evans Creek) with a greater percentage of their floods that are snowmelt floods, showing that average channel slope and likelihood of snowmelt flooding are not positively correlated (ruling out E). The passage indicates that a 100-year flood level is expected to be equaled or exceeded once every 100 years. It follows logically that a 5-year flood is expected to be equaled or exceeded once every 5 years, making its annual exceedance probability 20% (C).
The correct answer is A 5-year flood has a 20% annual exceedance probability.
2. For each of the following, select Yes if it is explicitly mentioned in the passage (Discussion) but not in the table. Otherwise select No.
The question asks for information explicitly mentioned in the Discussion but not the table.
RO1
Snowmelt floods is a column heading in the table, so it does not meet the question’s criterion.
The correct answer is No.
RO2
Absorptive capacity of soil does not appear in the table, but the Discussion lists it as a factor that affects the frequency of flooding onto floodplains.
The correct answer is Yes.
RO3
Drainage area is a column heading in the table, so it does not meet the question’s criterion.
The correct answer is No.
The question asks for information explicitly mentioned in the Discussion but not the table.
RO1
Snowmelt floods is a column heading in the table, so it does not meet the question’s criterion.
The correct answer is No.
RO2
Absorptive capacity of soil does not appear in the table, but the Discussion lists it as a factor that affects the frequency of flooding onto floodplains.
The correct answer is Yes.
RO3
Drainage area is a column heading in the table, so it does not meet the question’s criterion.
The correct answer is No.
3. For each of the following statements, select Yes if the information provided indicates that the statement is true. Otherwise select No.
RO1
Neither the Discussion nor the table provides information about the number of people affected by flooding, so there is no basis for determining the truth of this statement.
The correct answer is No.
RO2
Neither the Discussion nor the table provides information about the location of the rivers in Region X, so there is no basis for determining whether Evans Creek drains into Jackson River.
The correct answer is No.
RO3
According to the passage, a 100-year flood … is also considered a 1% annual exceedance probability flood. The table indicates that the area of the floodplain boundary of a 100-year flood for Deer Creek is 17 square kilometers.
The correct answer is Yes.
RO1
Neither the Discussion nor the table provides information about the number of people affected by flooding, so there is no basis for determining the truth of this statement.
The correct answer is No.
RO2
Neither the Discussion nor the table provides information about the location of the rivers in Region X, so there is no basis for determining whether Evans Creek drains into Jackson River.
The correct answer is No.
RO3
According to the passage, a 100-year flood … is also considered a 1% annual exceedance probability flood. The table indicates that the area of the floodplain boundary of a 100-year flood for Deer Creek is 17 square kilometers.
The correct answer is Yes.
