Geography IGCSE - Rivers

Water cycle

the journey water takes as it moves from the land to the sky and back again

Precipitation

transfer of water from atmosphere to Earth's surface in the form of hail, sleet, rain or snow

Interception

how precipitation is prevented from reaching the ground → usually by leaves or branches

Infiltration

Process where water enters the ground by seeping through soil or any other surface

Surface runoff

the flow of water that occurs when excess stormwater, meltwater, or other sources flows over the earth's surface

Throughflow

the water moving through the soil below the surface and above the water table

Percolation

The downward movement of water from the soil into the rock beneath

Groundwater flow

Water flows through the rock below the water table towards the river

River discharge

the volume of water flowing through a river channel

Transpiration

process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers

Evapotranspiration

all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration

Confluence

the point where 2 rivers meet

Drainage basin

area of land drained by a major river and its tributaries

Watershed

area of high land forming the edge of a river basin

Tributary

a small river or stream that joins a larger river

Bradshaw model

River erosion

River transportation

Solution: Minerals dissolve in water and move in solution

Suspension: Fine particles are carried within the water flow

Saltation: Small pebbles and stones bounce along the riverbed

Traction: Larger boulders and rocks roll along the bottom

River deposition

Decreasing velocity: Slower water flow reduces river’s capacity to carry material

Reduced gradient: Flatter riverbeds slow water flow → leads to sediment deposition

Increased width: Wider sections of a river have slower flow

Landforms of erosion

Long and cross profiles

Potholes

• Stones that have been broken by waterfalls and banks by hydraulic action have been transported down the river

• These rocks get rounded by the process of attrition

• When they reach small depressions they get stuck → force of the river water is not great enough to lift it out of the depression

• But if there is enough energy in the river flow, currents circulate around the depression and form eddies

• The rocks circulate, causing abrasion → drills down into the bedrock forming potholes 

• They vary in size depending on the force of the river

• Different sizes of potholes will eventually join → the rock in between these potholes will be eroded away

• Over long periods of time, potholes erode through the rock

Waterfalls

Develop where river flows over layer of hard rock followed by layer of softer rock → softer rock erodes more quickly through hydraulic action and abrasion → leads to undercutting of hard rock layer → unsupported hard rock collapses due to gravity → form steep drop that is characteristic of waterfalls

Meanders

Formed by erosion (outer bends) and deposition (inner bends) within river channel → process of hydraulic action and abrasion erodes outer banks → deposition of sediments on inner banks occurs where water flow has less energy → leads to formation of these sinuous curves in the river channel

Oxbow lake

Form from meanders that become extremely curved over time → during high-flow events → river may cut through a narrow neck of land → through hydraulic action and abrasion → shortens river path and leaving the meander loop cut off from the main flow → forms an oxbow lake

Delta

When rivers deposit sediments as they enter slower-moving or standing bodies of water → reduction in water velocity allows for deposition of sediments → gradually builds up delta over time → process of sedimentation creates these complex landforms characterized by multiple channels known as distributaries

Levees

When river overflows its banks in flood conditions → depositing heavier sediments close to river channel → process of deposition during flood events builds up the levees over time → creates natural embankments along river

Flood plains

Formed through deposition → when rivers flood and overflow their levees → sediment-laden water spreads out across the wider valley floor → deposits its load of sediments as water slows down → creates flat, fertile areas alongside rivers

Hazards from rivers

Flooding → residential areas near rivers, particularly in floodplains, are vulnerable to floods → lead to loss of life, damage to homes, destruction of infrastructure + economic losses

Erosion and Land Loss → riverbank erosion can threaten properties, agricultural land + infrastructure by washing away soil + ground stability → lead to displacement of communities + loss of arable land

Opportunities living near a river

Water resources → essential for human survival, providing water for drinking, cooking, bathing → also crucial for irrigating crops, supporting agriculture → backbone of many economies

Economy → facilitate various economic activities → fishing (supports livelihoods) transportation + trade (rivers are economical routes for transporting goods) + energy production → particularly hydroelectric power → major electricity source worldwide

Recreational + culture → recreational activities → boating, fishing, + watersports → important for leisure + tourism industries → culturally, rivers have been central to many societies, featured in rituals, festivals + sacred places

Habitat → provide habitats for diverse aquatic + terrestrial species → contributes to ecological health + biodiversity → not only crucial for environmental balance → also supports human life through ecosystem services