factors affecting stream energy & channel processes

Question 1

3 main factors

Answer 1

1. Resistance of bed material
2. Load calibre
3. Type of flow

Question 2

Resistance of material

Answer 2

More resistant rock type = mone energy needed for water to flow
- more collusive material (i.e. finer material) = fewer changes in channel morphology

Factors affecting:
- vegetation
- degree of particle consolidation& cementation
- particle size

Question 3

Load calibre

Answer 3

Size of individual particles carried by a river
- larger calibre seen in the upper course⇒ coarser sediments get deposited first upstream

Question 4

Flow type

Answer 4

More turbulent flow = mone energy required/used
- helicoidal flow ⇒ corkscrew motion (more turbulent)
- laminar flow ⇒ no mixing between layers of water

Question 5

3 channel processes

Answer 5

1. Deposition
2. Transportation
3. Erosion

Question 6

4 erosional processes

Answer 6

1. Hydraulic action → high velocity water dislodges particles/fragments of unconsolidated material
2. abrasion → mechanical breakage of sediment load by particles grinding against one another
3. corrosion → when chemical reactions take place with rock surfaces
4. attrition → breakdown of sediment load

Question 7

directions of erosion

Answer 7

1. vertical → downward cutting of the channel bed at the upper course
2. lateral → erosion of the channel banks, where there is side-cutting because of high discharge levels
3. headward → backwards erosion along the long profile, when adjusting to changes in stream energy

Question 8

deposition

Answer 8

when stream energy falls → river cannot carry existing sediments & maintain discharge levels → larger sediments get deposited [first]
- happens because of flow deceleration or precipitation events that cause the load calibre to increase

Question 9

3 transport processes

Answer 9

1. traction → transport of large particles via sliding & rolling on the channel bed
2. saltation → traction & suspension [particles get uplifted by turbulent forces & can set other particles in motion]
3. suspension → transport of FINE particles as suspended load