Chapter 16 Reading Assignment
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.
Which of the following are ways in which tectonism, such as an uplift of a mountain, can affect drainage?
-The uplift can increase the slope of the drainage. -The uplift can increase precipitation into the drainage. -The uplift can cause a rain shadow on the other side, causing a decrease in the runoff into the drainage. -The uplift can increase the supply of coarse sediment.
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
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
What is a drainage divide?
A ridge or strip of high ground separating one drainage basin from another
From the list below, select the characteristics of a braided river or stream.
Abundant sediments Steep gradient Variable flow
These are formed when a steep drainage enters a broad valley and the sediments and debris are deposited.
Alluvial fans
Which two of these do you multiply to determine the discharge of a river?
Area of the river Velocity of the river
The image shows a stream hydrograph of a flood where discharge is on the vertical axis, time is on the horizontal axis, and the red line is the flood stage. Which labeled point shows where the flood begins?
B, where the stream rises to the flood stage
What is the discharge for a river that is 5 meters deep, 15 meters wide, and has a stream velocity of 2 meters per second? m3/sec
Blank 1: 150
On a field trip, you measure the following: river depth = 7 feet; river width = 12 feet; and river velocity = 3 feet/sec. What is the discharge? ft3/sec
Blank 1: 252
What is the name for small, branching channels that carry water away from the main river channel and distribute it over the surface of the delta?
Blank 1: Distributaries
The part of the Mississippi River that carved itself a river valley over Cenozoic sedimentary rocks when sea level was low, and then filled the valley with deposits when sea level rose, is the Mississippi.
Blank 1: Lower
When steep, narrow drainages enter broader, more gentle valleys and streams deposit the large sediments they are carrying, form.
Blank 1: alluvial Blank 2: fans
The area that a stream naturally drains is called a drainage .
Blank 1: basin
The type of rivers that are characterized by a network of interweaving sinuous channels, with the overall channel being fairly straight, are rivers.
Blank 1: braided
One stream may divert the flow of another stream into a different basin through the process of stream . This occurs during erosion.
Blank 1: capture Blank 2: headward
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 and , which settle farther offshore.
Blank 1: clay Blank 2: silt
Besides sea level and rock type, the other two primary factors that influence a stream or river's profile are and .
Blank 1: climate or weather Blank 2: tectonics
As the gradient decreases in a river, the size of the sediment that can be transported .
Blank 1: decreases or declines
When the amount of sediment exceeds the ability of the current to carry it, the stream the sediment.
Blank 1: deposits
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.
Blank 1: discharge
A ridge or strip of high ground that separates one drainage basin from another is referred to as a drainage .
Blank 1: divide
A flood that is characterized by high discharge over a short time frame is called a(n) flood.
Blank 1: flash
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.
Blank 1: flooding or floods
A broad strip of land on either side of a stream channel that is covered by water during a flood and replenished by sedimentation is a(n) .
Blank 1: floodplain
Viscosity is the resistance to exhibited by fluids.
Blank 1: flow, movement, or motion
The force behind a river's flow from high to low elevations is .
Blank 1: gravity
The uplift of high mountain ranges increases slope and precipitation causing a subsequent in the amount of sediment available for a stream to transport.
Blank 1: increase
When a river floods and deposits sediment parallel to and along the river channel, a(n) is formed.
Blank 1: 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.
Blank 1: levees
The base level of a river is the elevation to which the river can erode.
Blank 1: lowest or minimum
A stream that flows year-round is a(n) stream, whereas a(n) stream does not flow the entire year.
Blank 1: perennial Blank 2: ephemeral or intermittent
The gradient, or of a stream is steeper near the headwaters than at the mouth.
Blank 1: profile or slope
Meandering rivers leave behind exposed curved ridges called meander marked by lines of vegetation or as curved dry depressions. When the depressions are filled with water, they are lakes.
Blank 1: scars Blank 2: oxbow
A tributary that itself has a tributary within a drainage system is a(n) -order stream.
Blank 1: second
The higher the velocity of a flowing stream, the larger its capacity to carry .
Blank 1: sediment
Construction of dams causes an interruption of river flow. River are deposited upstream of the dam, shortening the life of the reservoir.
Blank 1: sediments
Rivers and streams are similar bodies of flowing water. A(n) is a body of water with a current that flows downstream within a channel. A(n) is a large body of water with considerable volume and permanent or seasonal flow.
Blank 1: stream Blank 2: river
The 1993 flood of the Mississippi River at St. Louis began June 26 when the river reached the flood stage, and peaked August 1st. The flood peak was about feet above flood stage.
Blank 1: twenty or 20
The property of a fluid that is defined as the resistance to flow is .
Blank 1: viscosity
When comparing their ages, the Upper Mississippi is than the Lower Mississippi.
Blank 1: younger
Select the answer that is not a factor in the deposition of deltas.
Chemical makeup of sediment
What types of sediments or rocks are deposited by low-relief streams?
Clay Sand Silt
Which of the following is not a characteristic of a braided river or stream?
Constant flow
Select the human-caused flooding events from the list of flood causes below.
Dam failure Urbanization
______ are formed as rivers slow down when they reach their mouth and empty into an ocean.
Deltas
Match the type of sediment load to its description.
Dissolved <> Chemically soluble ions transported by the river Suspended <> Clay and silt carried indefinitely above the riverbed Bed <> Material carried on the bottom of a river by pushing, bouncing, rolling, and sliding; usually sand and gravel
Select all the natural causes for flooding from the list below.
Eruption of snow-covered volcano Local heavy precipitation Snowmelt Regional precipitation
Which drainage basin covers the largest area in the United States?
Gulf of Mexico
Which two drainage divides are separated by the Continental Divide?
Gulf of Mexico Pacific Ocean
What problems are associated with straightened or channelized stream channels?
Increased erosion downstream Reduced sediment deposition downstream Downstream flooding
Match the location of the diagram with a description of the shape of the river.
Left-side diagram <> Braided river Middle diagram <> River with low sinuosity Right-side diagram <> Meandering river
What types of streams typically deposit clay- to sand-sized sediments?
Low-relief streams
Which of the following physical parameters show a decrease from the headwaters to the mouth of a river?
Maximum grain size
______ 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
How long was the Mississippi River above flood stage in St. Louis during the summer of 1993?
Over 3 months
Select the three measurements needed to calculate discharge of a river at a certain point.
River depth Velocity of the water River width
What occurred to decrease the gradient of the Lower Mississippi River, causing it to deposit sediment within the valley it has previously incised?
Sea level rose.
Which of the following physical parameters show an increase from the headwaters to the mouth of a river?
Sediment load Discharge Channel size
What three factors of a drainage basin influence the flow response to rainfall?
Size Shape Slope
What are distributaries?
Small, branching channels that carry water away from the main channel
Which of these would indicate a flood on a stream hydrograph?
Stream discharge that is greater than the flood stage for the channel
Which of the following are primary factors that influence a stream's profile?
Tectonics Climate Sea level Rock type
A community experiences two floods with stream discharge equal to the 100-year recurrence interval. The floods occur in 1980 and 1990. When will or did the next flood occur?
The next 100-year flood could occur in any year.
What characteristics do rivers and streams share?
They flow downhill due to gravity. They can be braided or meandering. They flow within a channel.
From the list below, select the factors that control the deposition of a delta.
Wave action River and ocean ice Sediment load Vegetation Discharge
A decrease in the size of sediments carried by a river usually reflects ______ in the gradient of the river.
a decrease
Geologists use large water tanks in laboratories to study braided river dynamics. They control the slope, the ______, and the consistency of water flow to study how the variables affect the stream system.
amount and type of sediment
What is a drainage basin?
an area of land drained by a river and its tributaries
The lowest level to which a river can erode is its ______.
base level
The feature formed when a river deposits its sediment near its mouth is a(n) ______.
delta
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
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
A stream with no tributaries is a ______-order stream.
first
Large water tanks in laboratories are used by geologists to study water ______ in river systems because the tanks can be used to control the slope of the river and the type of sediments.
flow
The driving force behind a river's flow is ______.
gravity
Streams can expand the area of the basin by ______ which may lead to ______.
headward erosion; stream capture
The profile of a river is steeper at its ______.
headwaters
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
The probability that a discharge of a certain size will occur during any given year is calculated using ______.
historic raw data
As water velocity in a stream increases, turbulence increases, resulting in a(n) ______ in the water's ability to erode and transport sediment within a channel.
increase
The Upper Mississippi River ______.
is young was created by glacial meltwaters
A flash flood ______.
lasts a short time often results from intense rainfall
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
When meander scars are filled with water, they are ______.
oxbow lakes
A stream or river that flows all year is ______.
perennial
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 ______ load is the total amount of sediment carried by a river.
sediment
The size of the drainage basin and the ______ the drainage basin influence the flow response to rainfall.
shape of
We disrupt the balance of a river system when we discourage the process of migration and meandering by ______ streams.
straightening
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
The graphs geologists use to estimate river flow probability are ______.
unique to each stream
The turbulence of water increases as the water's ______ increases, which can increase the water's ability to erode and transport materials within the channel.
velocity
A stream deposits the sediment it is carrying ______.
when it no longer has the capacity to do so
