Channel types Flashcards
What are the 3 channel types?
1) Straight
2) Meandering
3) Braided
What is the sinuosity of a river channel?
A measure of how ‘bendy’ it is
How is the sinuosity of a river calculated?
By dividing the length of the river channel by the length of the valley in which it flows.
Why does water not ever flow in a straight line?
The thalweg moves around stones and other obstructions, causing areas of slow and fast water movement.
Why does a river develop a meandering pattern?
As a need to distribute energy, and is driven by the thalweg.
What is a point bar?
A gently sloping deposit of sand, gravel and pebbles.
What causes meanders to form?
Where the river swings towards the bank (thalweg) erosion causes undercutting. On the inner bank, material is deposited due to less velocity.
Continued erosion causes a river cliff or bluff to form.
A point bar forms on the inner bank (river beach)
Also helicoidal flow contributes to this, as when it hits the outer bank it corkscrews, flows along the river bed and deposits eroded material on the inner bank.
What is a braided river channel?
One that is divided into smaller channels by temporary islands called eyots.
Where do braided channels form?
Where there is:
- Significant amounts of sedimentary load
- A steep profile
- A regularly fluctuating discharge
Why do braided channels form?
When the rivers carrying capacity is exceeded, the river deposits its load into the channel and eyots and bars form.
