1.River Processes Flashcards
What is erosion?
The breaking down of rock by a moving agent e.g. the river
Erosion is a key process in shaping landscapes by removing material.
Define transportation in the context of river systems.
The carrying of load by the river
Transportation is crucial for the movement of sediments downstream.
What occurs during deposition?
The drop in energy in the river and resulting dropping of transported load
Deposition leads to the formation of various landforms like deltas.
What is hydraulic action?
The force of the water into the bed and banks as well as the pressure of air being compressed into cracks
Hydraulic action is a significant erosional process.
Explain abrasion (or corrasion).
The sandpaper effect of load grinding against the bed and bank
Abrasion shapes riverbeds and banks through physical wear.
What is solution (corrosion) in river processes?
The weak chemical reaction of water that dissolves minerals in rock
This process is particularly important in limestone regions.
Define attrition.
The breaking down of rocks and pebbles as they knock into each other
Attrition contributes to the rounding of sediment particles.
What is vertical erosion?
The cutting down of the river into the bed, deepening the channel
Vertical erosion is most prominent in the upper course of rivers.
What is lateral erosion?
The cutting in of the river to the bank, widening the channel
Lateral erosion is significant in the middle course of rivers.
Differentiate between traction and saltation.
Traction is the rolling of bedload along the bed; saltation is the bouncing of bedload along the bed
Both are key methods of sediment transportation.
What is suspension in river transportation?
The transportation of suspended load (clays, mud) in the flow of water
This method allows fine particles to be carried over long distances.
Define capacity in the context of rivers.
The total amount of load being transported in the river
Capacity is influenced by flow velocity and sediment size.
What does competence refer to in river systems?
The maximum size of individual rocks the river can transport
Competence varies with flow velocity.
Describe how erosion patterns change from the upper to lower course of a river.
The upper course is dominated by erosion; the middle course focuses on transportation; the lower course is characterized by deposition
This progression is influenced by energy levels and sediment load.
What is the effect of peak flow on hydraulic action?
Hydraulic action is greatest during times of peak flow and floods
Increased flow leads to enhanced erosional power.
True or False: Abrasion is more common in the lower course of rivers.
False
Abrasion is more prevalent in the upper course due to more exposed bedrock.
What are the main types of river transportation?
Bedload (traction and saltation), suspended load (suspension), and dissolved load (solution)
Each type of transportation operates under different conditions.
Fill in the blank: The division between transportation and _______ is small.
deposition
A slight decrease in flow velocity can lead to significant deposition.
What characterizes dynamic braided environments?
Frequent changes in discharge, flow velocity, and variations in erosion, transportation, and deposition
Braided channels are often found in glacial and arid environments.
What is the time scale of river processes in braided rivers?
High frequency, lasting over hours and days
In more defined environments, processes can take tens to hundreds of years.
