One characteristic of a meandering stream is its erosion pattern.
The erosion pattern in the form of gravel bars is concentrated along the outside of the turn in between meanders or near any place where there are obstacles or constrictions on the stream.
This gives evidence that it moves around quicker than areas upstream and downstream, which doesn’t have any erosional deposits since water moves more slowly over time.
A meandering stream moves around quicker than an area upstream or downstream because the water’s velocity is accelerated when it turns downhill (water accelerates when it falls).
It also flows kinematically outward in one side and inwards in the other side; this is called superpositioning.
These two flow patterns create a slight which deflects the water all the way to its outer bank, which causes erosion.
This occurs because of the water velocity and the gradient of the stream. The velocity is how fast water travels, and it can be determined by surface area per time; therefore, velocity is proportional to gradient.
Together, this results in a quick decrease in depth and width of a river over time because of erosion from moving velocities and gradients.
Where is erosion concentrated along a meandering stream?
1. Along the outside of the turn in between meanders or near any place where there are obstacles or constrictions.
2. Where water moves quickly because of moving velocities and gradients (acceleration) caused by water flow and water falls.
3. The density of the erosional deposits is concentrated along the outside of the turn in between meanders.
4. The concentration of erosional deposits is greater than other areas (water moves quickly over time) because the constrictions force water velocity to accelerate, resulting in faster movement and greater erosion.
5. The speed due to surface area (velocity) and gradient are larger downstream than upstream because there are more obstacles or constrictions on the stream.
Also, there’s less distance per time traveled so velocity is greater.
6. The speed (velocity) of water is greater downstream because the surface area is larger.
7. It’s more difficult to move water over obstacles along a meandering stream because of the gradient and velocity; therefore, there’s more resistance along the outermost part of the turn in between meanders. This results in erosion on the outside.
8. The flow pattern creates sediment deposits mainly on the outside of a meandering stream with sharp turns; this happens because there are many obstacles and constrictions on its banks that force water velocity to accelerate (accelerate “augmented by friction”).
9. The flow pattern results in erosion along the outermost part of the turn in between meanders because there are less obstructions on the banks and water is moving faster.
10. The increase of erosion over time increases with distance downstream and becomes more concentrated because of friction (movement over obstacles or constrictions).
11. The speed is greater upstream than downstream not because velocity increases but because distance traveled decreases as velocity increases:
V=d/t
where V = m/s, which is proportional to gradient; t = s, which is proportional to time.
12. The speed of water upstream is slower because of friction caused by obstacles and constrictions along the stream banks.
13. The speed of water downstream is faster than upstream because there’s less friction due to the angle of the stream and less obstruction along banks; therefore, more velocity (speed) is created.
14. Velocity increases as the angle decreases and there are fewer obstructions on banks (less friction).
15. The flow pattern results in erosion on the outside of a meandering stream because it’s easier to move over obstacles along a straight path than one that curves.
16. The erosional patterns show greater consistency along the outermost part of a meandering stream because it’s easier to see velocity and acceleration over time; this is called superpositioning, as water flows kinematically outward in one side and inwards in the other side.
17. The flow pattern affects erosion because it depends on friction, sediment concentration, and obstruction of banks (obstacles or constrictions).
18. The flow pattern affects erosion because it depends on the surface area and obstacles that decrease velocity and increase friction.
19. The flow pattern affects erosion because it depends on the surface area, friction, concentration of sediment, and how fast water moves over time (acceleration).
20. Why are there erosional deposits on the outside of a stream? It’s easier to move over obstacles from a straight path than one that curves (straight “leads”).
Also, water is less likely to move against the flow; therefore, all water tends to go with the flow (downhill) resulting in increased velocities that create greater friction and erosion.
