Physical Landscapes UK: River Landscapes and Processes Flashcards
Hydrological cycle
Moves water between the land, sea and atomosphere:
1) Evaporation
2) Transpiration
3) Condensation
4) Precipitation
5) Surface flow
6) Infiltration
7) Through flow
8) Groundwater flow
9) Percolation
10) Interception
Transpiration
Water lost through leaves of plants.
Precipitation
Moisture falling from clouds as rain, snow or hail.
Surface runoff
Water flowing over surface of land into rivers.
Infiltration
Water absorbed into the soil from the ground.
Interception
Vegetation prevents water from reaching the ground.
Source
Start of a river.
Tributary
Smaller rivers that join to larger ones.
Confluence
Where 2 rivers join.
Mouth
End of a river, usually where a river joins the sea.
Watershed
Edge of river basin, usually highland.
Drainage basin
A catchment area for precipitation. Rain is drained by one river and its tributaries. Every river has a drainage basin.
Upper course features
When a river is near its SOURCE, it often develops V-SHAPED valleys as the river erodes DOWN (vertical erosion).
The GRADIENT here is STEEP and the river CHANNEL is NARROW.
VERTICAL erosion also causes the river to wind and bend to avoid areas of hard rock. This creates INTERLOCKING SPURS.
When a river runs over alternating layers of hard and soft rock, RAPIDS and WATERFALLS may form.
Formation of a waterfall:
When a river flows over different bands of rock:
1) Soft rock erodes more quickly, undercutting the hard rock.
2) Hard rock is left overhanging and because it isn’t supported, it eventually collapses.
3) Fallen rocks crash into the plunge pool at base of waterfall. They swirl around, causing more erosion.
4) Over time, this process is repeated and the waterfall moves upstream.
A steep-sided gorge is formed as the waterfall retreats.
Middle course features
In the middle course the river has MORE ENERGY and a HIGH VOLUME of water.
The GRADIENT here is GENTLE and LATERAL (sideways) EROSION has WIDENED the river CHANNEL.
The river channel has also DEEPENED. A larger river channel means there is LESS FRICTION, so the water FLOWS FASTER.
Lateral erosion causes the formation of MEANDERS and, eventually, OXBOW LAKES.
Oxbow lake
Over time, meanders start to erode towards each other.
Gradually the neck of the meander narrows until is is completely broken through to form a new straighter channel.
Water now takes the shortest route through the thalweg and deposition seals off the old meander, forming an oxbow lake.
Lower course features
In the lower course, the river has a HIGH VOLUME and a LARGE DISCHARGE.
The river CHANNEL is now DEEP and WIDE and the LANDSCAPE is FLAT. The river now has a wide FLOODPLAIN.
As a river reaches the end of its journey, ENERGY levels are LOW and DEPOSITION takes place. ESTUARIES are found at the mouth.
Meander
A bend in the river formed by lateral erosion + deposition.
Erosion + a river cliff are found on the outside of the bend. Water flows fastest (thalweg) there, where water flow has most energy due to decreased friction.
Deposition + a slip off slope are found on the inside of the bend, where there is more friction and water flow is slower.
Floodplain
A wide, flat area of marshy land on either side of the river that is covered in times of a flood. Found in middle and lower courses.
Made of alluvium, which is the sediment deposited during floods.
Floodplains are used for agriculture as alluvium is very fertile.
Formed when meanders reach end of floodplain due to lateral erosion, which widens the valley.
Levee
A raised riverbed formed by flooding over many years.
When a flood occurs, the river loses energy. The largest material is deposited first on the sides of the river banks and smaller material further away.
Water spreads the sediment out across the floodplain, building up the levee.
After many floods, the river bank is higher, so the channel can carry more water and flooding is less likely to occur in the future.
Estuary
Transitional zone between the river and the sea. The main process effecting estuaries is deposition.
During a rising tide river water can’t flow into the sea. The river’s velocity falls and sediment is deposited.
At low tide these deposits form mudflats. Overtime, mudflats develop into important natural habitats called saltmarshes.
River case study: River Tees
Location and Background
Located in North of England and flows 137km from the Pennines to the North Sea
River case study: River Tees
Upper course
- Source high in the Pennine Hills
- High Force is UK’s largest waterfall at 21m high made from harder Whinstone and softer limestone rocks
- Plunge pool
- Gorges
- Rapids
- Vertical erosion has formed V-shaped valleys
- Rocks are smoothed as they move down the river by attrition
- Bed load of large rocks
River case study: River Tees
Middle course
- Lateral erosion has formed meanders near Barnard Castle
- Floodplains
- 95% land is farmland
- River is very powerful here
- Bed load is much smaller
River case study: River Tees
Lower course
- Meanders are much larger and oxbow lakes have formed near Yarm
- Levees have formed when river has flooded
- River not as powerful here
- Very large estuary with mudflats and sandbanks, which support wildlife in the area
- Very industrially developed
- Mouth at North Sea