rivers

Question 1

sliding

Answer 1

Downhill movement of large amounts of rock, soil or mud. Occur on steep slopes that have been previously weakened by weathering.

Question 2

Slumping

Answer 2

Occurs after long periods of rainfall. The rains seeps through the permeable rock, when it meets impermeable rock the highly saturated soil and weaker rock moves in a rotational manner along a curved surface.

Question 3

Valley profile in upper course

Answer 3

V-shaped in upper course as the river has the potential to erode vertically, as it is way above sea level.

Question 4

Gradient change throughout the river.

Answer 4

Gradient decreases as the river moves downstream as the river begins to erode laterally

Question 5

Discharge change throughout the river.

Answer 5

Increases as the river moves downstream as width and depth increase and velocity increases.

Question 6

information about River Creedy

Answer 6

Flows 16km through Devon.
Upper course is shallow and narrow with a steep gradient.
Middle course meets the River Binneford and river becomes wider and deeper.
Lower course meets the river Yeo creating lateral erosion forming meanders.

Question 7

Formation of waterfalls.

Answer 7

A waterfall is a sudden drop along the river course. It forms when there are horizontal bands of hard rock positioned over exposed, less resistant soft rock.

1. The soft rock is eroded quicker than the hard rock and this creates a step.
2. As erosion continues, the hard rock is undercut forming an overhang.
3. Abrasion and hydraulic action erode to create a plunge pool.#
4. Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
5. This process continues and the waterfall retreats upstream.
6. A steep-sided valley is left where the waterfall once was. This is called a gorge.

Question 8

Formation of meanders.

Answer 8

As the river makes its way to the middle course, it gains more water and therefore more energy. Lateral erosion starts to widen the river. When the river flows over flatter land they develop large bends called meanders.

As a river goes around a bend, most of the water is pushed towards the outside. This causes increased speed and therefore increased erosion (through hydraulic action and abrasion).

The lateral erosion on the outside bend causes undercutting of the bank to form a river cliff.

Water on the inner bend is slower, causing the water to slow down and deposit the eroded material, creating a gentle slope of sand and shingle.

The build-up of deposited sediment is known as a slip-off slope (or sometimes river beach).

Question 9

Oxbow lakes.

Answer 9

Due to erosion on the outside of a bend and deposition on the inside, the shape of a meander will change over a period of time. Erosion narrows the neck of the land within the meander and as the process continues, the meanders move closer together. When there is a very high discharge, the river cuts across the neck, taking a straighter and shorter route. Deposition will occur to cut off the original meander, leaving an oxbow lake.