GEOL100 Chapter 16

Discharge =

(width) x (depth) x (velocity)

Characteristics of a braided stream

- Abundant sediments - Steep gradient - Variable flow

Which parameters increase as they go down from headwaters to the delta?

- Channel size - Discharge rate - Sediment load

Which factors affect stream profile?

- Climate - Rock type - Tectonics - Sea level

match the condition on the left with the effect on the river of drainage system on the right:

- Dam: Changes the base level because of sediment buildup - Tectonism: Can increase the slope and supply of coarse sediments - Runoff: Increases flow, causing flooding - Geology: Streams erode soft rocks more easily than hard rocks - Vegetation: Plants stabilize stream bank and protect against erosion

Match the type of sediment load to its description:

- Dissolved: chemically soluble ions - Suspended: Clay and silt carried above riverbed - Bed: materials carried on the bottom of the river

What features characterize low gradient rivers?

- Floodplains - Meanders - Point-bars - Single channels - Stream terraces

Which conditions have an effect on river flow system?

- Geology - Tectonism - Human engineering - Runoff - Climate - Vegetation

Factors that control the deposition of a delta are:

- Ice in streams and the sea - Vegetation - Wave erosion - Discharge - Sediment load

How does tectonism affect drainage?

- Increases slope - Increases supply of broad sediment - Increased precipitation flowing into drainage - Creates a rain shadow for the other side

Which of the following describes the great flooding in the Colorado river?

- It was measured by geomorphologists - It occurred before any settlement - Had an estimated discharge of 8500m^3/s

What conditions caused the Mississippi river flood of 1993?

- Severe precipitation caused by warm, moist air from the Gulf of Mexico and Cold dry Arctic air meeting. - Already saturated grounds

3 factors that influence drainage basin response to rainfall are:

- Slope - Shape - Size

Ranks stages of terrace formation in order:

1. Deposition of sediment occurs on the floodplain. 2. A drop in the base level of the river results in downcutting through deposits. 3. Further downcutting occurs, and the river abandons the previously formed floodplain. 4. The oldest floodplain becomes isolated as the river downcuts, leaving a terrace.

Order the sequence of layers as delta build further out:

1. Horizontal beds 2. Cross bedded sediments 3. Marine clays

How is an entrenched meander created?

1. River flows across floodplain 2. Tectonic activity causes uplift 3. Further incision caused by flow

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.)

1. Winter 2. Fall 3. Summer 4. Spring

What is a 100-year flood?

A flood with a 1% chance of occurring a year

What is a bedrock stream?

A mountainous stream flowing through carved bedrock channel

An erosional base level of a river can be _____ .

An ocean, a lake or a closed land basin

Antecedent vs superposed

Antecedent: Incises its surrounding geology Superposed: is confined by its surrounding environment

What is evidence that the Mississippi river moved over the last 7000 years?

At least six abandoned deposit marks where deltas were created.

_____ are created as flowing water collects in natural cracks and capture additional runoff.

Channels

What type of sediment is most common in floodplains?

Clay and Silt

Human-caused floods are created by which events?

Dam failure and urbanization

Which graph has a concave up shape?

Elevation profile???

Problems associated with channelizing a stream and countering its sinuosity?

Flooding, increased erosion and reduced deposition downstream

What is a dendritic flow pattern?

It is generally tree-like

What are the two large reservoirs created by damming in the Colorado river?

Lake Powell and Lake Mead

Features that occur along the Colorado river include:

Lakes, Geological structures, Dams, Lava flows

What caused the gradient of the lower portion of the Mississippi river to flatten?

Rise in sea levels

What are distributaries?

Small, shifting channels that distribute sediments throughout the surface of a delta away from the main river

How do mountainous streams obtain their sediment?

Soil/sediment slides down drainage area, tributaries bring sediments to drainage area

Wtf are "eddies"?

Swirls within a current caused by increased velocity and turbulence.

What is stream abrasion?

The process of grains chipping, scraping and sandblasting the streambed as they moved downstream.

What is an alluvial fan?

When a steep drainage enters a broad valley and sediments are deposited

Where and when does a graded stream occur?

When there is stability in conditions such as climate.

An area that a stream naturally drains is called a drainage _____ .

basin

Flat bottomed valleys between mountains is where _____ rivers can be found.

braided

Deposition occurs when water velocity _____ .

decreases

Potholes are formed when water flows in small _____ in the rock.

depressions

Outside of meander, velocity is _____ while on the inside it is _____ .

faster, slower

A flood that is characterized by high discharge over a short time frame is called a _____ .

flash flood

Any drainage basin can erode upward in a process called _____ . This can lead to _____ , the natural diversion of water from one stream into another

head-ward erosion, stream capture

Origin of a river is the _____ , and the end is called the _____ .

headwaters, mouth

Channel beds erode faster than channel sides in _____ streams.

higher velocity, turbulence and gradient

The _____ the stream velocity, the _____ it's capacity to carry sediment.

higher, larger

The upper portion of the Mississippi river _____ .

is young and was created by glacial meltwater

Flooding can be prevented by constructing _____ .

levees

A(n) _____ stream or river is one that flows year-round, whereas a(n) _____ stream does not flow the entire year.

perennial, intermittent

A sandbar deposited along the inside of a stream meander due to lower velocity is called the _____ .

point-bar

Two main driving forces behind a stream are _____ .

precipitation and gravity

Nickpoints can form a _____ .

rapid or waterfall

The type of sediment transport that involves a series of leaps or bounces off the bottom of a steamed is known as _____ .

saltation

A river can not erode below _____ .

sea-level

The amount that a channel curves for a given length is its _____ .

sinuosity

River _____ are relatively flat benches perched above rivers/streams and step upward.

terraces