Rivers Flashcards
What is a river regime?
The annual pattern of discharge in a river during the year in response to precipitation, temperature, evapotranspiration, and drainage basin characteristics
Name 5 factors that affect river discharge
- Shape of the land
- Climate
- Soil type
- Urbanisation
- Antecedent moisture
What is a river?
A body of water that flows in open channels
Why are rivers known as dynamic?
Due to many variables; precipitation, temperature, drainage basins, erosion, overland flow etc.
What is the dynamic equilibrium?
The constantly adjusting balance of the river channel shape, due to changes in inputs of water and material.
What are the two key ideas relating to the rivers energy and efficiency?
- Mannings equation
- Hydraulic radius
How is hydraulic radius calculated?
Cross sectional area/wetted perimeter.
What does a higher hydraulic radius indicate?
The more efficient the river is, therefore the faster it will flow with more energy.
What is lateral erosion?
Erosion that makes a river wider, and usually occurs in the middle and lower course.
What is vertical erosion?
Erosion that makes a river deeper, and happens more in the upper course.
What is headward erosion?
Erosion that makes a river longer, and happens near the source. This is due to surface run off and through flow causing erosion at the point where water enters the valley head.
How are potholes formed in a river?
- River water is swirled around in irregular patterns in the river bed, creating vertical eddies
- Rocks are quest into small depressions and abrade the hollow deeper, these rocks are known as grinders
- This process continues, deepening the river bed into potholes
What is the competence of the river?
The maximum size of load a river is able to carry
What is the capacity of the river?
The total volume of material a river can transport.
What causes a river to lose energy?
When discharge or velocity decreases, usually close to river barns and shallow areas.
