Fluvial Systems

Question 1

Describe the drainage system of the Amazon River

Answer 1

• 7,050,000 km2

- Q = 209,000 m3 s-1

Question 2

Describe the drainage system of the Mississippi River

Answer 2

• 2,981,076 km2

- Q = 16,792 m3 s-1

Question 3

What are desert micro catchments?

Answer 3

Designed to increase run off from rain

Question 4

Outline Hortons stream morphometry

Answer 4

• Measures the shape of streams
• Channels originating at source with no tributaries are 1st order
• When two streams of order join, a stream of order ω + 1 is created
• When two streams of different order join, the segment downstream has the higher order

Question 5

What are river channels?

Answer 5

River channels are 3 dimensional features

Question 6

What are the 3 main types of river channels?

Answer 6

• Straight
• Meander
• Braided

Question 7

What is aggradation?

Answer 7

• The deposition of material by a river, stream, or current

- Sediment supply > transport capacity = aggradation

Question 8

When is erosion caused in a river channel?

Answer 8

Sediment supply < transport capacity = erosion

Question 9

Why is sediment important for river channels?

Answer 9

• All sediment in river comes from mountains and moves downstream
• The movement of sediment is key for enabling the growth and collapse of bedrooms (dunes) and landforms (deltas)

Question 10

What are the 3 different types of sediment load?

Answer 10

• Bedload
• Suspended load
• Dissolved load

Question 11

What is the equation to measure river discharge and material fluxes?

Answer 11

Q = W X D X V

- Measures cross section

Question 12

What is the principle of mass conservation?

Answer 12

Principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system’s mass cannot change, so quantity can neither be added nor be removed

Question 13

What is an alluvial system?

Answer 13

A landform produced when a stream or river, that is, some channelized flow slows down and deposits sediment that was transported either as bedload or in suspension

Question 14

How are rivers self formed alluvial systems?

Answer 14

• Over geological time scales, river channels adjust through erosion and deposition to carry their discharge
• Use the energy of flowing water to perform geomorphic work – displace material downstream
• Carve a form (cross section and planform, slope and grain size) to carry their discharge and sediment load

Question 15

What are equilibrium channel forms?

Answer 15

• Channel equilibrium occurs when all 4 variables are in balance
• Adjustable variables: width, depth, slope, planform, sediment cover
• River form adjusts so that for a prevailing discharge and sediment load, the flows in bank and the bed sheer stress sufficient to transport the sediment, but not cause erosion or deposition