GY 102 Assignment 8

During the 1993 upper _________ River flood, floodwaters flowed onto the floodplain because levees did not hold the water back. It took months for the floodplains to dry out because the ________ trapped the water, preventing it from flowing back into the river channel.

1. mississippi 2. levees

Steep slopes in a(n) _________ canyon plus an unusually large thunderstorm resulted in the 1976 Big Thompson River flood near Estes Park, _________

1. narrow 2. colorado

A 500-year flood has a 1/ ________ probability of occurring during any given year.

500

A 10-year flood event, or one that has a 1/10 chance of occurring during any given year on this river, would have a discharge of approximately ______ m3/s. a. 1,200 b. 275 c. 2,000 d. 400

a. 1,200

What is the probability that a flow event will reach 800 m3/s in any given year on this stream? a. 20% b. 80% c. Can't deduce from the information on the chart d. 0% e. 100%

a. 20%

The discharge of the Mississippi River in St. Louis stayed above flood stage continuously for over ______ days in 1993 (as shown on this hydrograph.) a. 90 days b. 60 days c. 30 days

a. 90 days

Select the human-caused flooding events from the list of flood causes below. a. Dam failure b. Local heavy precipitation c. Volcanic eruption d. Urbanization e. Regional precipitation f. Snowmelt

a. dam failure d. urbanization

Select all the natural causes for flooding from the list below. a. Eruption of snow-covered volcano b. Hydroelectric dam failure c. Regional precipitation d. Snowmelt e. Dense urbanization f. Local heavy precipitation

a. eruption of snow covered volcano c. regional precipitation d. snowmelt f. local heavy precipitation

Which of the following are considered to be special causes for severe flooding events? a. Prolonged drought followed by intense precipitation b. Failure of a dam c. Rainfall coinciding with snowmelt and ice dams in a river d. Stalled hurricane e. Oil spills and oily tides

a. prolonged drought followed by intense precipitation b. failure of a dam c. rainfall coinciding with snowmelt and ice dams in a river d. stalled hurricane

Select the two conditions that resulted in the 1993 upper Mississippi River flood. a. The ground was already saturated from early spring rains. b. Several dam breaches along the tributaries of the Mississippi River happened at once. c. Severe precipitation was caused by warm moist air from the Gulf of Mexico and cold Arctic air merging.

a. the ground was already saturated from early spring rains. c. severe precipitation was caused by warm moist air from the gulf of Mexico and cold Arctic air merging.

The term "100-year flood" signifies ______. a. the size of a flood that is predicted to have a 1 in 100 probability of occurring in a given year b. a general term for a very large flooding event c. the size of a flood that is predicted to occur every year for 100 years continuously

a. the size of a flood that is predicted to have a 1 in 100 probability of occurring in a given year.

In what ways do streams impact people's lives? a. They provide floodplains with nutrients required by plants and crops. b. They are the top source of atmospheric carbon dioxide, a greenhouse gas. c. They allow for the generation of energy without the release of carbon dioxide. d. They are used as transportation routes.

a. they provide floodplains with nutrients required by plants and crops. c. they allow for the generations of energy without the release of carbon dioxide. d. they are used as transportation routes.

Select the three measurements needed to calculate discharge of a river at a certain point. a. Velocity of the water b. River length c. River width d. River depth

a. velocity of the water c. river width d. river depth

If you examined a hydrograph and saw a peak discharge in a small amount of time, then a quick decline in discharge, what might have been a possible explanation for the peak? a. A slow melting from a snow-packed mountain b. A heavy rainstorm event upstream

b. a heavy rainstorm event upstream.

If you examined a hydrograph and saw an extended peak discharge over a fair amount of time, then a slow decline in discharge, what might have been a possible explanation for the peak? a. A heavy rainstorm event upstream b. A slow melting from a snow-packed mountain

b. a slow melting from a snow packed mountain.

True or false: Modern and affordable human-constructed levee systems can last forever. a. True b. False

b. false

Which of the following statements best represents the lessons of history regarding the use of levees as a flood prevention method? a. Levees have proven to be essentially useless. b. Levee systems invariably fail, and affordable systems cannot withstand the largest floods. c. Where levee systems are built, river towns are protected from flooding.

b. levee systems invariably fail, and affordable systems cannot withstand the largest floods.

The cross-sectional area of the channel of a stream or river is calculated by ______. a. dividing the channel's depth by its width b. multiplying the channel's width by its average depth c. multiplying the channel's depth by its average length d. adding the channel's width and average length

b. multiplying the channels width by its average depth.

The ability to determine the ______ of a flooding event is based on river flow data. The more data collected and the greater the time span for data collection, the better understanding we have of the chance of future flooding events. a. timing b. probability c. length

b. probability

A flash flood occurs when ______. a. the vast majority of the water in the channel is experiencing turbulent flow b. water level quickly rises over flood stage and then falls rather quickly c. water in a floodplain becomes deep enough to achieve laminar flow d. a flood occurs without discharge officially reaching flood stage

b. water level quickly rises over flood stage and then falls rather quickly.

What two measurements are required to determine the cross-sectional area of a stream at a specific location? a. Water velocity b. Water temperature c. Average depth of water d. Average width of channel e. Height of channel banks

c. average depth of water. d. average width of channel.

Which of the following summaries best describes how flooding by streams impacts humans? a. Floods have a completely positive impact on people as they create flat land suitable for farming. b. Floods are completely negative in human terms considering the damage caused. c. Floods have both negative and positive aspects as they cause destruction and yet also provide floodplains with sediments and nutrients.

c. floods have both negative and positive aspects as they cause destruction and yet also provide floodplains with sediments and nutrients.

The more years of river flow data that are collected, the ______ the probability of predicting a major flooding event. a. riskier b. lower c. higher

c. higher

Select the conditions that caused the 1976 Big Thompson River flood near Estes Park, Colorado. a. Failed earthen dam upstream b. Heavily developed banks along the river c. Narrow canyon d. Steep slopes of the river canyon e. Unusually severe thunderstorm

c. narrow canyon d. steep slopes of the river canyon e. unusually severe thunderstorm

______ are formed beside low-gradient rivers when floods occur and sediments build up along the channels. These features become barriers to water returning to the river from the floodplain. a. Meander scars b. Point bars c. Natural levees d. Oxbow lakes

c. natural levees

The hydrograph of the Mississippi River in St. Louis during the 1993 flooding event shows increases in discharge due to prolonged ______ upstream and decreases in discharge due to ______ and the eventual ending of the natural disaster. a. drought; precipitation b. snowmelt; human diversions c. precipitation; levee breaches

c. precipitation; levee breaches

What is a flood? a. Erosion exceeds deposition along the river channel bed. b. Precipitation exceeds infiltration for a single event. c. Water overflows a stream's channel.

c. water overflows a streams channel.

What does a hydrologic gauging station do? a. Tries to prevent flooding by compacting water in specialized pipes b. Tries to prevent flooding by piping water to water catchment areas c. Cools or warms the water in an effort to adjust the amount of dissolved oxygen in the stream d. Measures and records real-time data about a stream's flow

d. measures and records real time data about a streams flow.

How is flood stage defined? Flood stage is reached when ______. a. the slope in the plot of the change in discharge over time is greater than one b. the slope in the plot of the change in discharge over time is greater than two c. the discharge is greater than it has been in a predefined amount of time (e.g., ten years) d. the amount of discharge needed to overtop a stream's banks and spill onto the floodplain is reached

d. the amount of discharge needed to overtop a streams banks and spill onto the floodplain is reached.

The volume of water flowing through a stretch of a river is the _________ and is measured by multiplying the river depth by river width and river velocity.

discharge

When a stream's discharge rapidly rises above and then quickly falls below flood stage, it is known as a _______ flood.

flash

The amount of discharge needed to overtop a stream's banks and spill onto the surrounding land is the ______ stage.

flood

Human-constructed barriers such as levees are beneficial because they can help prevent _________; however, it is difficult to construct an affordable levee that will not fail during the worst situations.

flooding

Stream measurements are collected continuously and automatically at a(n) _______ station.

gauging

Catastrophic flooding often accompanies _______ like Mitch in 1998 that stalled over Central America and brought 75 inches of rain.

hurricanes

A natural ______ is created when a river floods and deposits sediment parallel to and along the river channel.

levee

Flooding can be prevented by building _________ parallel to river channels. However, these structures do fail, and construction to prevent the worst possible flooding events is not affordable.

levees