GY Final Lecture Exam- Topic 8
In what ways do streams impact people's lives?
-They allow for the generation of energy without the release of carbon dioxide. -They are used as transportation routes. -They provide floodplains with nutrients required by plants and crops.
From the list below, select the characteristics of a braided river or stream.
-Variable flow -Abundant sediments -Steep gradient
What two measurements are required to determine the cross-sectional area of a stream at a specific location?
-Average width of channel -Average depth of water
Which of the following locations would be the two most common areas in which to find a braided stream or river?
-Broad, sloping plains that flank mountain ranges -Flat-bottomed valleys between mountains
At a flow velocity of 12 cm/sec, which of the following statements are true?
-Clay is transported as suspended sediment. -Most sand sizes are transported as bedload.
Select the conditions that caused the 1976 Big Thompson River flood near Estes Park, Colorado.
-Narrow canyon -Steep slopes of the river canyon -Unusually severe thunderstorm
Select all the natural causes for flooding from the list below.
-Regional precipitation -Snowmelt -Local heavy precipitation -Eruption of snow-covered volcano
Select the three measurements needed to calculate discharge of a river at a certain point.
-River depth -River width -Velocity of the water
Select the two conditions that resulted in the 1993 upper Mississippi River flood.
-Severe precipitation was caused by warm moist air from the Gulf of Mexico and cold Arctic air merging. -The ground was already saturated from early spring rains.
Select common features located along low-gradient rivers.
-Single channels -River terraces -Floodplains -Meanders
Which of the following are considered to be special causes for severe flooding events?
-Stalled hurricane -Prolonged drought followed by intense precipitation -Failure of a dam -Rainfall coinciding with snowmelt and ice dams in a river
Select conditions that have an effect on the flow of river systems over time.
-Tectonism -Runoff -Dams -Geology -Climate
Why does the discharge of a stream change during the course of a year?
-The amount of precipitation can vary by season. -The type of precipitation can vary during the year. -Influx from groundwater can vary during the course of a year.
Select consequences to a river when a dam is constructed.
-The dam causes the river to deposit its sediment load upstream of the dam. -The dam creates a temporary base level for the river. -Water released from the dam is clear (no sediment) and has a new capacity to erode and transport sediments downstream.
From the list below, select the factors that control the deposition of a delta.
-Vegetation -Wave action -River and ocean ice -Discharge -Sediment load
The erosional base level of a river can be ______.
-a closed land basin -an ocean -a lake
Order the sequence of layers produced as a delta builds out into the oceans from flowing rivers, as you would see them in a cross section.
1. Horizontal beds deposited partly on land 2. Cross-bedded sediments 3. Marine clays
Summarize changes to stream systems in the US southwest since the mid-1800s by putting the sentences in the correct chronological order from top to bottom.
1. Settlers built farms on floodplains that were at the same level as the streams. 2. Wetter climate patterns resulted in an increase in stream erosion; some parts of the old floodplain were abandoned and dried up. 3. Changes in climate patterns resulted in channel deposition and rebuilding of floodplains.
Rank the seasons from the lowest discharge of water to the highest for a river located in the Upper Midwest of the U.S. (Place the season with the lowest discharge on top.) -Spring -Winter -Summer -Fall
1. Winter 2. Fall 3. Summer 4. Spring
What is the probability that a flow event will reach 800 m3/s in any given year on this stream?
20%
The elevation of a river at its headwater is 735 meters, and at its mouth is 685 meters over a distance of 2000 km. The gradient of the river is 1m/(BLANK) km.
40
A 500-year flood has a 1/(BLANK) probability of occurring during any given year.
500
The discharge of the Mississippi River in St. Louis stayed above flood stage continuously for over ______ days in 1993 (as shown on this hydrograph.)
90
What is a floodplain?
A broad strip of land built up by sedimentation on either side of a stream channel and covered with water during a flood
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 heavy rainstorm event upstream
What is a drainage divide?
A ridge or strip of high ground separating one drainage basin from another
What is a point bar?
A sandbar deposited along the inside of a stream meander due to lower velocity
What is a drainage network? --A series of interconnected streams that when combined drains a larger area than any one stream -The different types of flows in a single channel that combine to move water downstream -The combined processes (e.g., evaporation) that remove water from streams -A system of streams that loses all of its surface water before reaching base level
A series of interconnected streams that when combined drains a larger area than any one stream
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 slow melting from a snow-packed mountain
Match the type of sediment load to its description. A) Dissolved B) Suspended C) Bed
A) Dissolved- Chemically soluble ions transported by the river B) Suspended- Clay and silt carried indefinitely above the riverbed C) Bed- Material carried on the bottom of a river by pushing, bouncing, rolling, and sliding; usually sand and gravel
A) Structurally controlled pattern B) Radial drainage pattern C) Dendritic drainage pattern
A) Structurally Controlled- Drainage occurs on eroded layers or structures and then cuts across a ridge to follow a different weak layer. B) Radial Drainage-Drainage is found on symmetrical mountains such as volcanoes. C) Dendritic- Treelike pattern develops on rocks with similar resistance to erosion.
Where is the approximate location of the fall line on this profile?
C
Rank the following particle sizes transported by water from smallest to largest. (Place the smallest particle size at the top.) Sand Silt Clay Boulders Cobbles
Clay, Silt, Sand, Cobbles, Boulders
What kind of changes occurred to stream systems in the US southwest in the last 200 years in response to changes in precipitation?
Deposition and erosion both created and changed the size and position of floodplains.
What is the term for small, shifting channels that carry water away from the main river channel and distribute it over the surface of the delta?
Distributaries
Which of the following summaries best describes how flooding by streams impacts humans?
Floods have both negative and positive aspects as they cause destruction and yet also provide floodplains with sediments and nutrients.
Catastrophic flooding often accompanies (BLANK) like Mitch in 1998 that stalled over Central America and brought 75 inches of rain.
Hurricane
What is the problem often caused by hardening a stream channel to prevent erosion or flooding in one area?
Increased rates of erosion downstream
What is the Fall Line in the eastern United States?
It is a line of rapid elevation change from the resistant rocks of the Piedmont to the softer sediments of the coastal plain.
What is stream abrasion?
Large grains collide with other grains in a stream and break them into smaller pieces
Which of the following statements best represents the lessons of history regarding the use of levees as a flood prevention method?
Levee systems invariably fail, and affordable systems cannot withstand the largest floods.
Which of the following best describes the migration of meanders across a floodplain?
Meanders continue to migrate as they continuously erode and deposit material.
What does a hydrologic gauging station do?
Measures and records real-time data about a stream's flow
During the 1993 upper (BLANK) 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 (BLANK) trapped the water, preventing it from flowing back into the river channel.
Mississippi; levees
On the diagram shown, look at the channel profile at the place labeled "cutbank." Where is the deepest water? The shallowest water?
On the outside of the bend; on the inside of the bend
The Colorado River starts in the (BLANK) Mountains, and its delta is in (BLANK).
Rocky; Mexico
At a flow velocity of 100 cm/sec, which of the following statements is true regarding sand-sized sediment?
Smaller sand grains are transported as suspended sediment, and larger grains are transported as bedload.
With respect to the seasons, the highest discharge of a river in the Upper Midwest is usually in the (BLANK) and the lowest discharge is during (BLANK).
Spring; Winter
True or false: The amount of winter snowfall and the rate at which it melts in the spring can greatly affect the timing and amount of discharge in a stream.
True
What is a flood?
Water overflows a stream's channel.
A decrease in the size of sediments carried by a river usually reflects ______ in the gradient of the river.
a decrease
The headwaters of the Colorado River ______, and the mouth is at the Gulf of California.
are in the Rocky Mountains
Oceans, lakes, or the bottoms of closed basins are all (BLANK) levels of rivers.
base
A drainage (BLANK) is an area in which all drainages merge into a single stream or move to a single body of water.
basin
A (BLANK) stream flows in a network of many interconnected rivulets around numerous bars.
braided
Flat-bottomed valleys between mountains would be good places to look for ______ rivers or streams.
braided
Which of the following physical parameters increase from the headwaters to the mouth of a river?
channel size, sediment load, velocity, discharge
Which of the following is not a characteristic of a braided river or stream?
constant flow
The (BLANK) at the end of the Colorado River has changed dramatically in response to the cutoff water supply now used for drinking and irrigation.
delta
When rivers enters a lake or an ocean, they slow down and lose their capacity to carry sediments, forming ______.
deltas
______ are formed as rivers slow down when they reach their mouth and empty into an ocean.
deltas
(BLANK) drainage patterns are associated with areas where the rocks have the same resistance to erosion, whereas (BLANK) drainage patterns are found on symmetrical mountains.
dendritic, radial
When the amount of sediment exceeds the ability of the current to carry it, the stream (BLANK) the sediment.
deposits
Potholes or bowl-shaped pits are formed when flowing water and sediments swirl in small (BLANK) in the rock.
depressions
What parameters do you need to know to calculate the discharge of a river?
depth, width, velocity
The direction of stream flow from higher elevations to lower elevations is referred to as the ______ direction.
downstream
Streams often combine their flows and in doing so remove water from a larger area than any one stream does. This interconnected system of streams forms a(n) ______.
drainage network/stream system
The gradient of a stream or river is defined as the change in (BLANK) for a given horizontal distance.
elevation/height
Some of the most beautiful, and photographed, sections along the Colorado River are the (BLANK) meanders that first formed their curvy paths before uplift allowed them to cut down through the rocks.
entrenched
Rivers and streams (BLANK) the landscape, carry the materials, and later deposit the sediments, thereby acting as major sculptors of Earth's surface.
erode
A(n) (BLANK) is a broad strip of land on either side of a stream channel that is covered by water during a flood and replenished by sedimentation.
floodplain
What is the word used to describe the change in elevation for a given stream or river over a horizontal distance?
gradient
(BLANK) is the force behind a river's flow from high to low elevations.
gravity
The driving force behind a river's flow is ______.
gravity
The two primary forces that drive a river system are ______ and ______.
gravity; precipitation
In flowing water, the upstream side of an obstruction is subjected to the ______ of abrasion.
greatest amount
The profile of a river is steeper at its ______.
headwaters
The origin of a river is called its (BLANK) , and the end of a river is called its (BLANK).
headwaters, mouth
The more years of river flow data that are collected, the ______ the probability of predicting a major flooding event.
higher
The ______ the velocity of a river, the ______ its capacity to carry sediment.
higher; larger
A(n) (BLANK) is a type of graph used to display the change in a river's discharge over time.
hydrograph
The channel size, discharge, velocity and sedimentary load of a stream ______ downstream, and the maximum sediment grain size ______.
increases; decreases
What is the difference between a centripetal and radial drainage pattern? In a radial drainage pattern, the flow ______.
is outward in all directions, and a centripetal pattern is when the flow is inward from several directions
The current location of the Mississippi River Delta is heavily controlled by human interference; the nature of this delta system ______.
is to create and abandon deltas in different locations
A natural (BLANK) is created when a river floods and deposits sediment parallel to and along the river channel.
levee
Flooding can be prevented by building (BLANK) parallel to river channels. However, these structures do fail, and construction to prevent the worst possible flooding events is not affordable.
levees
Meanders, floodplains, and river terraces are commonly found along (BLANK) gradient rivers.
low
The base level of a river is the (BLANK) elevation to which the river can erode.
lowest
Stream channels rarely stay straight and quickly develop (BLANK) due to differences in roughness on the channel bottom.
meanders
The discharge of a river is measured in cubic (BLANK) per second.
meters
The size of sediments in braided rivers typically is ______ than that carried by meandering rivers.
more varied
The cross-sectional area of the channel of a stream or river is calculated by ______.
multiplying the channel's width by its average depth
The volume of water flowing through any part of a river per unit of time (discharge) is calculated by ______.
multiplying the velocity by the cross-sectional area of the river
Steep slopes in a(n) (BLANK) canyon plus an unusually large thunderstorm resulted in the 1976 Big Thompson River flood near Estes Park, (BLANK) .
narrow; Colorado
______ 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.
natural levees
Trellis and annular drainage patterns are similar in that they are both structurally controlled. How do they differ? A trellis pattern follows ______.
one structure before cutting across a ridge and following a different structure and an annular pattern follows curved layers around a central area
What type of lake is created when a cutoff meander becomes isolated? The answer is just one word.
oxbow
When meander scars are filled with water, they are ______.
oxbow lakes
A stream or river that flows all year is ______.
perennial
A(n) (BLANK) stream or river is one that flows year-round, whereas a(n) (BLANK) stream does not flow the entire year.
perennial; intermittent/ephemeral
A depositional feature that has been built on the inside of a stream channel curve because of lower velocity is a ______.
point bar
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.
precipitation; levee breaches
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.
probability
The (BLANK), or gradient, of a stream is steeper near the headwaters than at the mouth.
profile/slope
Erosion and deposition by (BLANK) are the principal processes that sculpt Earth's landscape.
rivers or streams
The movement of sand grains by a series of short leaps or bounces along a streambed is (BLANK).
saltation
The type of sediment transport that involves a series of leaps or bounces off the bottom of a streambed is ___________.
saltation
Meander (BLANK) are left behind by meandering rivers as exposed curved ridges, lines of vegetation, or as curved, dry depressions. When the depressions are filled with water, they are (BLANK) lakes.
scars, oxbow
A delta is formed where a river meets a(n) ocean because (BLANK) is deposited as the river loses speed.
sediment
The total amount of sediment carried by a river is the ______.
sediment load
The amount that a river or stream channel curves in a given length is called its (BLANK).
sinuosity
Dissolution is the process by which (BLANK) materials are removed and transported by flowing water.
soluble/dissolved/water-soluble
The hydrograph for a steeply-sloped basin will peak ______ than that for a basin with gentle slopes.
sooner
How does stream aggradation occur? Aggradation occurs as ______.
streams deposit more sediment than they erode and by doing so increase the stream's gradient
How is flood stage defined? Flood stage is reached when ______.
the amount of discharge needed to overtop a stream's banks and spill onto the floodplain is reached
A hydrograph shows ______.
the change in a river's discharge over time
The term "100-year flood" signifies ______.
the size of a flood that is predicted to have a 1 in 100 probability of occurring in a given year
Smaller subsidiary channels that feed the main channels of rivers are ______.
tributaries
What is the name of the subsidiary channels that join up with the main river channel?
tributaries
Use the following information to calculate the gradient of River X. If the vertical change is 10 meters in 1 kilometer, then the gradient expressed in m/km is ______.
10
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.
1200
If a large section of a stream is channelized by artificially straightening and hardening the bottom or sides, what will be the result of this action immediately downstream?
Erosion will increase as the higher velocity stream can erode more and deposit less sediment.
What does downstream mean?
It is the direction of flow in which the water is moving.
In a meandering river, the deeper outside bend is eroded into the (BLANK), and on the shallower oppostite side of this is a(n) (BLANK).
cutbank, point
Select the human-caused flooding events from the list of flood causes below.
dam failure; urbanization
As the gradient decreases in a river, the size of the sediment that can be transported
decreases
A(n) (BLANK) is formed where a river meets the sea, slows down, and deposits its sediments.
delta
The amount of water flowing through a channel over a given amount of time is called its ______.
discharge
The volume of water flowing through a stretch of a river is the (BLANK) and is measured by multiplying the river depth by river width and river velocity.
discharge
Soluble materials in flowing water are removed and transported by a process called ______.
dissolution
The numerous small channels that run over this delta in multiple directions are called (BLANK).
distributaries
A ridge or strip of high ground that separates one drainage basin from another is a drainage (BLANK).
divide
On the outside of a meander, the water velocity is faster and causes ______, and on the inside of a meander, the water velocity is slower, which causes ______.
erosion; deposition
True or false: Modern and affordable human-constructed levee systems can last forever.
false
True or false: The Mississippi River delta has been located in the same place for at least 10,000 years.
false; Reason: It has moved at least 6 times, and we are now trying to keep it in place.
Meanders cause differences in water velocity in the river channel. On the outside of a meander, water velocity is ______ and causes erosion, while on the inside of a meander, water velocity is ______ and deposition of sediments occurs.
faster; slower
When a stream's discharge rapidly rises above and then quickly falls below flood stage, it is known as a (BLANK) flood.
flash
A(n) (BLANK) is an event in which the amount of water flowing through a river channel overflows its banks.
flood
Human-constructed barriers such as levees are beneficial because they can help prevent (BLANK); however, it is difficult to construct an affordable levee that will not fail during the worst situations.
floods
Stream measurements are collected continuously and automatically at a(n) (BLANK) station.
gauging
When is sediment most likely to be deposited? When the ______.
sediment supply exceeds a stream's capacity to transport it
Construction of dams causes an interruption of river flow. River (BLANK) are deposited upstream of the dam, shortening the life of the reservoir.
sediments
The size of the drainage basin and the ______ the drainage basin influence the flow response to rainfall.
shape of
What three factors of a drainage basin influence the flow response to rainfall?
shape, size, slope
The particle size transported by water that is in between clay and sand is (BLANK).
silt
When a river enters an ocean and begins depositing sediments to form deltas, the first particles to settle out are large particles and sand followed by (BLANK) and (BLANK), which settle farther offshore.
silt, clay