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GEOG 1190 > Chapter 15 - River Systems > Flashcards

Chapter 15 - River Systems Flashcards

1
Q

River

A

a river is water in a channel on the surface of the Earth moving downhill due to gravity

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2
Q

Drainage Basin

A

the area of land drained by a river.

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3
Q

Drainage divide

A

the high point of land that separates water flow. The limits of a drainage basin marked by ridges and highlands.

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4
Q

Summarize the process of water flow down a drainage basin

A

3 STEPS

  • The water that collects high in the drainage basin, nearest the divide, is in many small channels.
  • converge into fewer, larger channels
  • eventually all the water flows out of the basin in a single large channel.
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5
Q

Summarize the process of water flow down a drainage basin through channels

A

3 STEPS

  • the water that collects high in the drainage basin, nearest the divide, is in many small channels.
  • these channels eventually converge into fewer, larger channels
  • eventually all the water flows out of the basin in a single large channel.
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6
Q

Deranged Pattern

A
  • common in Canadian North
  • result of three contributing factors:
  1. the ground is permanently frozen (permafrost).
  2. there is a lot of exposed bedrock
  3. there are many old glacial deposits
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7
Q

How is permafrost a contributing factor to the formation of a Deranged drainage pattern?

A

Because the ground is frozen, it’s difficult for surface water to erode a channel.

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8
Q

How are exposed bedrock and old glacial deposits contributing factors to the formation of a Deranged drainage pattern?

A

They block or deflect flow.

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9
Q

Two common types of river

A
  1. Meandering

2. Braided

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10
Q

Braided River Features

A
  1. Number of channels:more than 1
  2. Size of channel:smaller
  3. Shape of Channelwide and shallow
  4. Discharge:variable
  5. Sediment Load:poorly sorted coarse or large moving as bedload
  6. Gradient:Steep
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11
Q

Meandering River Features

A
  1. Number of channels:1
  2. Size of channel:larger
  3. Shape of Channelwide and Deep
  4. Discharge:consistent and stable
  5. Sediment loadwell sorted, fine or small moving in suspension
  6. Gradient

shallower

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12
Q

Fluvial or river erosion

A

The way in which a river sets sediment in motion

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13
Q

3 ways fluvial erosion occurs

A

THE IMPACT OF

  1. moving water
  2. sediment that is already moving

Together these two processes are ABRAISION

  1. Hydraulic lift
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14
Q

Hydraulic lift

A

When moving water flows around a grain and it cannot move, it speeds up (velocity increases)

At the the same time, pressure decreases as the water flows around this grain

As a result the grain is lifted upward and set in motion.

If it doesnt lift the sediment grain off the river bed, it reduces contact so that the water around it can move it.

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15
Q

Fluvial Transport

A

How sediment already in motion is moved by a river.

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16
Q

Fluvial Transport modes

A
  1. Solution
  2. Suspension
  3. Saltation
  4. Traction
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17
Q

SOLUTION as a mode of Fluvial Transport

A

Dissolved elements or molecules carried throughout the river. These are deposited when they precipitate.

example: sodium and chlorine dissolved in the water, and they precipitate (salt).

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18
Q

SUSPENSION as a mode of Fluvial Transport

A

The finest/smallest solid particles that are carried in the water. This sediment rarely makes contact with the channel bottom.

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19
Q

SALTATION as a mode of fluvial transport

A

These are larger sediment grains that bounce along the bottom making frequent but only short term contact with the channel bottom.

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20
Q

TRACTION as a mode of fluvial transport

A

The largest sediment in motion. These grains roll or slide along the bottom. (too heavy!)

21
Q

Traction and saltation together make up…

A

BEDLOAD

22
Q

Fluvial Deposition

A

How sediment in a river stops moving.

23
Q

When does deposition of solid particles occur?

A

when water velocity drops

24
Q

Threshold or critical velocity

A

The water velocity necessary to set in motion (erode) a grain of a certain size

25
Q

Why are very small grain sizes (<0.002mm) harder to erode?

A

Because they often contain clay minerals. Clay minerals are flat, sheet-like grains.

Clay minerals are flat, sheet-like grains that have an electric charge on their surface. This means that clay minerals stick together and are hard to erode.

26
Q

Thalweg

A

The place in the river where the deepest, fastest water is..

27
Q

Cut Bank is a product of ____

A

erosion

28
Q

Point Bar is a product of _____

A

deposition

29
Q

Where is the fastest water (Thalweg) found?

A

The fastest water is found next to the outside bank of the river where it erodes sediment to produce a CUT BANK.

30
Q

Where is the slowest water found?

A

next to the inside bank of the river where it deposits sediment to produce a POINT BAR

31
Q

Once a bend or meander in a river starts to form the process will continue until..

A

well developed meanders form as channels migrate laterally

32
Q

3 FACTORS controlling the FORMATION OF A DELTA

A
  1. River (dominated delta)
  2. Wave (dominated delta)
  3. Tide (dominated delta)
33
Q

River dominated delta

A
  • the delta grows into the lake or ocean.
  • a number of longer, linear extensions grow as multiple channels transport and deposit sediment.

Example: Mississippi “Bird Foot Delta”

34
Q

Wave dominated delta

A

Waves originating on the lake or ocean will rework sediment at the front of the delta to create beaches.

35
Q

Tide dominated delta

A

Sediment on the surface of the delta is reworked into a series of linear bars by the back and forth motion of water as the tide rises and falls.

36
Q

Rivers flood only ____ly and when they do the size of the flood will ___. Not all rivers have flood ___

A

Rivers flood only rarely and when they do the size of the flood will vary. Not all rivers have flood plains

37
Q

flood plain

A

A flat, low-lying area along a stream channel, created by and subject to recurrent flooding

38
Q

Flooding can be prevented, or at least minimized by artificial structures such as ___

A

Levees

39
Q

Flood hydrograph

A

A graph plotting river discharge over time

40
Q

Describe flooding in urban settings (hydrograph)

A

In an urban setting water collects quickly due to hard, impermeable surfaces and enters the river channel quickly It also drops quickly.

41
Q

Describe flooding in rural settings (hydrograph)

A

In a rural setting the ground is more porous i.e. farm fields and covered in vegetation. These ensure that water collects more slowly and moves through the river system over a longer period of time

42
Q

Describe flooding in rural settings (hydrograph)

A

In a rural setting the ground is more porous i.e. farm fields and covered in vegetation. These ensure that water collects more slowly and moves through the river system over a longer period of time

43
Q

Levees

A

elevated banks of a river

44
Q

Fluvial processes

A

processes that are related expressly to streams and rivers

45
Q

Drainage density

A

total length of all stream channels in the basin divided by the total area of the basin

46
Q

Base Level

A

level below which the stram cannot erode its valley

47
Q

Discharge

A

Volume of flow in a river that passes by a given point in a given unit of time. (cubic metres per second)

48
Q

Most important thing to remember about the four things used to define a river

A

They are all related

49
Q

The dominant processes controlling channel processes is..

A

climate which controls precipitation, which . controls discharge

GEOG 1190 (7 decks)

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