landforms made by rivers

Question / Term

Answer / Definition

What are the main processes that shape river landforms?

Erosion, transportation, and deposition — working together over time to sculpt valleys, meanders, floodplains, and deltas.

What is river erosion?

The wearing away of the riverbed and banks by the flowing water and its load.

Name the four main erosion processes in rivers.

Hydraulic action, abrasion (corrasion), attrition, and solution (corrosion).

Hydraulic action

The force of moving water compresses air in cracks and breaks rock apart along the banks and bed.

Abrasion (Corrasion)

Eroded material carried by the river scrapes and grinds against the channel, wearing it away like sandpaper.

Attrition

Rock fragments carried by the river collide, breaking into smaller, smoother, and rounder pieces.

Solution (Corrosion)

River water dissolves soluble minerals (e.g. limestone, chalk), contributing to erosion by chemical action.

What factors influence the rate of river erosion?

Gradient (slope), velocity, volume of water, and sediment load.

Describe the long profile of a river.

The gradient of a river from its source (steep) to its mouth (gentle), typically concave in shape.

What are the three stages of a river?

Upper course (erosional), middle course (transportational), and lower course (depositional).

Upper course characteristics

Steep gradient, narrow V-shaped valleys, interlocking spurs, vertical erosion dominant.

Middle course characteristics

Gentler slope, wider valley, lateral erosion increases, meanders form.

Lower course characteristics

Very gentle slope, wide floodplains, deep channel, deposition dominant, deltas may form.

Vertical erosion

Downward cutting of the riverbed that deepens the valley, common in upper course.

Lateral erosion

Sideways erosion that widens the valley, most active in middle and lower courses.

Transportation (in rivers)

The movement of eroded material downstream by the flowing river.

List the four methods of river transportation.

Traction, saltation, suspension, and solution.

Traction

Large boulders and rocks roll along the riverbed due to strong current.

Saltation

Small pebbles bounce or hop along the riverbed, lifted temporarily by the flow.

Suspension

Fine particles like silt and clay are carried within the water column.

Solution (transportation)

Dissolved minerals are carried in the river water invisibly.

When does deposition occur in a river?

When the river loses energy — usually when it slows down, enters a gentler gradient, or meets still water.

What factors cause a river to lose energy?

Decrease in gradient, reduction in discharge, increase in friction, or when entering a lake or sea.

Landforms of the upper course

V-shaped valleys, interlocking spurs, waterfalls, and gorges.

How do V-shaped valleys form?

Vertical erosion deepens the valley; weathering weakens slopes, causing material to collapse and form a “V” shape.

Interlocking spurs

Projections of high land that alternate from each side of a valley, formed when the river winds around harder rock.

Formation of a waterfall

Occurs when a river flows over alternating layers of hard and soft rock; soft rock erodes faster, creating a drop.

How does a gorge form?

The waterfall retreats upstream due to undercutting and collapse, leaving a steep-sided gorge behind.

Landforms of the middle course

Meanders and oxbow lakes.

How does a meander form?

Lateral erosion occurs on the outer bend (fast flow) and deposition on the inner bend (slow flow), creating a curve.

What is a river cliff?

The steep, eroded outer bank of a meander formed by hydraulic action and abrasion.

What is a slip-off slope?

The gentle inner bank of a meander where sediment is deposited due to slower flow.

Formation of an oxbow lake

The neck of a meander narrows due to erosion, and during flooding, the river cuts through; the loop is cut off, forming a lake.

Landforms of the lower course

Floodplains, levees, deltas, and estuaries.

Floodplain

The wide, flat area of land on either side of a river that floods periodically, receiving layers of deposited silt.

How does a floodplain form?

Lateral erosion widens the valley, and repeated flooding deposits sediment, creating a flat fertile plain.

Levee

Natural embankments of sediment along riverbanks formed when a river overflows and deposits heavy material first.

How do levees form?

During floods, heavier materials are deposited near the banks, building up raised ridges over time.

Delta

A depositional feature where a river meets still water (sea or lake) and deposits sediment faster than it can be removed.

Conditions needed for delta formation

Low tidal range, gentle gradient, and large sediment supply.

Three main types of deltas

Arcuate (fan-shaped), bird’s foot, and cuspate.

Estuary

The tidal mouth of a large river where freshwater mixes with seawater; sediment is deposited in tidal mudflats.

Why are river deltas and floodplains fertile?

Because of frequent deposition of nutrient-rich alluvium.

River rejuvenation

A renewed period of vertical erosion due to a fall in base level or land uplift.

Features formed by river rejuvenation

River terraces, incised meanders, and knickpoints.

What are river terraces?

Step-like landforms along valley sides, remnants of former floodplains left after renewed downcutting.

Incised meander

A meander that cuts deeply into the landscape due to renewed vertical erosion.

Knickpoint

A sudden change in river gradient, often marking where rejuvenation began (like a mini-waterfall).

Human impacts on river systems

Dams, channelization, deforestation, and urbanization can alter flow, increase erosion, or disrupt sediment transport.

How do dams affect river landforms?

They trap sediment, reduce downstream deposition, and may cause increased erosion below the dam.

Why is understanding river landforms important?

It helps manage flood risks, plan land use, and understand natural landscape evolution.