river landforms

cross profile

cross section of a river's valley and channel.

used to display the channel changes (width, depth, etc.)

Vertical erosion

involves the wearing away and deepening of the river bed. It is common in the upper course

- as the river flows downhill there is an increase in vertical erosion.

lateral erosion

causes the widening of a particular stream channel. It is common in the middle course

upper course

waterfalls, gorges, interlocking spurs, v shaped valley, rapids

Waterfall

descent of a river or stream over a vertical or very steep slope in its bed.

- Waterfalls occur in the upper and middle courses of rivers.

how Waterfall forms

Occur when rivers flow over layers of soft & hard rock.

- soft rock is eroded more easily, this leads to the hard rock being undercut.

- A ledge of hard rock forms until it breaks and collapses into the plunge pool.

gorge

narrow, steep sided valley, often formed as a waterfall retreats upstream.

how is a gorge formed

formed as a waterfall retreats up a valley. This happens when a river flows over a band of hard rock that lies over the top of the softer, less resistant rock.

rapids

part of a stream where the water flows very swiftly over rocks

Interlocking spurs

caused because the river wants to erode vertically. It therefore winds it way around areas of hard rock, avoiding them in favour of softer rock which is more easily eroded and leaves them as ridges

middle course

wider, shallower valleys, meanders, and oxbow lakes.

lower course

wide flat-bottomed valleys, floodplains and deltas.

type of erosion in the upper course

VERTICAL EROSION

type of erosion in the middle course

LATERAL EROSION

type of erosion in the lower course

deposition

Deposition

laying down of sediment carried by wind, flowing water, the sea or ice.

erosion

Processes by which rock, sand, and soil are broken down and carried away

Potholes

smooth, rounded hollows in the bedrock of the river

in the upper course

Deltas

When a river meets the sea its velocity suddenly reduces. This reduction in velocity means that much of the rivers load is deposited at the mouth of the river. If the river deposits quicker than the sea can erode then a delta starts to develop

types of delta

Arcuate or fan-shaped

Cuspate

Bird's foot

Arcuate or fan-shaped

land around the river mouth arches out into the sea and the river splits many times on the way to the sea, creating a fan effect.

Cuspate

land around the mouth of the river juts out arrow-like into the sea.

Bird's foot

river splits on the way to the sea, each part of the river juts out into the sea

Meander

a bend in the river. usually occur in the middle or lower course, and are formed by erosion and deposition

How meanders form

- due to both deposition and erosion and meanders gradually migrate downstream.

- The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction.

- On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction.

Over time the horseshoe become tighter, until the ends become very close together.

Ox Bow Lakes/C shaped lakes

formed when meanders continually erode

Riffles

areas of shallow water created by deposition of coarse sediment.

Helicoidal Flow

A corkscrewing motion responsible for the formation of meanders

river cliff

This is a feature formed on the outside of a meander where the fast moving water erodes the banks

River beach/slip-off slope

This is a feature formed on the inside bend of a meander due to deposition

discharge

the quantity of water in a stream that passes a given point in a period of time

Levees

Embankment of sediment along the bank of a river. It may be formed naturally by regular flooding or be built up by people to protect the area against flooding.

how are leeves formed

formed by the repeated flooding of the river. When the river floods, the biggest, most coarse material will be dumped close to the river banks.

Floodplains

area of land which is covered in water when a river bursts its banks.

A floodplain is a very fertile area due to the rich alluvium deposited by floodwaters

How are floodplains formed?

form due to both erosion and deposition. Erosion removes any interlocking spurs, creating a wide, flat area on either side of the river.

alluvium

deposited silt from a river flood