Water On The Land Flashcards Preview

Geography > Water On The Land > Flashcards

Flashcards in Water On The Land Deck (82):
1

Alluvium

Rock particles (clay, silt, sand, gravel) deposited by a river

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Attrition

Erosive process where particles of load and knocked about as they are transported and gradually become more rounded/reduced in size

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Base level

Altitude of the mouth of the river and point where the gradient becomes zero. No further erosion possible during normal river flow at this point

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Bed load

Material carried by a river by being bounced or rolled along it's bed

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Channel

Course for the river water (straight or meandering)

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Condensation

When water vapour changes to liquid

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Confluence

Point at which 2 or more rivers meet

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Cross profile

Shape of a slice across a river

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Deforestation

Removal of a forest/stand of trees where land is thereafter converted to a non-forest use

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Delta

River mouth choked with sediment causing the main channel to split into smaller branching channels or distributaries

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Depth

Measurement of the distance between the bed of the river and surface. Increases downstream (joined by lots of tributaries)

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Discharge

Volume of water passing a specific point at a given time. Becomes larger downstream (many tributaries join). Cross sectional area x velocity (cumecs - cubic metres per second m3/sec)

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Drainage basin

Land that is drained by a river and it's tributaries enclosed by the watershed

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River engineering

Steps that can be taken to manage flooding. Often involve trying to lengthen amount of time it takes for water to reach river channel (increasing lag time). Can be hard or soft

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Erosion

Wearing away of bed and banks of river channel by abrasion, hydraulic action, solution and attrition

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Estuary

The tidal mouth of a river with large flat expanses of mud exposed at low tide

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Evaporation

Water lost from the ground/vegetation surface

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Flood plain

Wide, flat floor of a river valley. It consists of fertile sediments (alluvium) deposited by the river during flood conditions

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Flood plain zoning

Procedure used to identify areas of varying flood hazard and therefore constructing buildings of high land value away from areas of flood risk

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Gorge

Steep-sided narrow rocky valley marking the retreat of a waterfall

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Gradient

Slope of river profile, steep close to the source, gradually becoming more gentle until the river reaches sea level

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Groundwater

Water stored in rock beneath the surface

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Groundwater flow

Water flowing through the rock layer parallel to the surface

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'Hard' options

River management that tends to be more expensive and have a greater impact on the river and the surrounding landscape (forceful human intervention)

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Hydraulic action

An erosive process where the sheer force of the water by itself can erode material from the bed and banks of the river channel

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Infiltration

Water sinking into soil from the ground surface

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Interception

Water being prevented from reaching the ground by trees or other vegetation. A store of water

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Interlocking spurs

As the river descends from the highland it begins to meander between spurs which interlock down the valley

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Lateral erosion

Erosion by a river on the outside of a meander channel. It eventually leads to the widening of the valley and the formation of the flood plain

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Levées

River embankments built by deposition as the river floods (natural or man-made)

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Load

The material transported by a river as bedload, suspended load or dissolved load (in solution)

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Long profile

A slice through the river from source to mouth

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Lower course

The section of the river near the sea, where deposition is the most important process and the valley becomes wider and flatter

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Meander

A bend in the river. The outside of the meander has the fastest flow and deepest water

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Middle course

The section of the river between the mountains and the lowland, where transport of eroded material is important and the river begins to cut sideways due to the reducing gradient

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Mouth

Where a river ends, at a lake or the sea

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Oxbow lake

A meander which has been cut off from the main river channel and abandoned

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Peak discharge

Maximum discharge in a river

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Peak rainfall

Time period on a flood hydrograph when the most rain fell

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Percolation

Water seeking deeper below the surface, often from the soil into the bedrock

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Pervious

A soil which allows relatively free movement of water

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Plunge pool

Deep pool below a waterfall

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Precipitation

Any source of moisture reaching the ground eg. snow, rain, frost

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Profile

The cross-section of the river from it's source to it's mouth concave in shape

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Rapids

Found where the river meets a band of resistant rock and usually precede a waterfall

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River cliff

Steep sided slope, created on the outside of a meander bend by the erosive effect of fast-flowing water

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Saltation

A process of transport; material bounced along the bed of the river

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Sedimentation

The settling out of suspended particles from a body of water (or in some cases very fine particles settled from the air or blown by the wind)

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Slip-off slope

Forms on the inside of a meander bend as a result of deposition in the slower flowing water

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'Soft' options

Flood protection that is more ecologically sensitive

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Solution

Some rocks such as limestone are subject to chemical attack and slowly dissolve in the water

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Source

Where a river starts, usually in the mountains

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Straightening meanders

This involves digging a straighter shorter channel in areas where rivers meander. The logic behind this is to speed up water flow in flood prone areas and stop water from 'hanging around'

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Storm hydrograph

Graphs that show how a drainage basin responds to a period of rainfall. They are useful in planning for food situations and times of drought

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Surface run-off (overland flow)

Water flowing on top of the ground

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Surface storage

Water held on the ground surface eg. puddles/ponds

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Suspended load

Very small and light material, usually find clay and silt, transported by the river suspension

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Throughflow

Water flowing through the soil layer parallel to the surface

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Traction

Material rolled along the bed of the river

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Transpiration

Water lost through pores in vegetation

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Transportation

The river moves material as bedload, suspended load or dissolved load (in solution). Bedload can be moved by saltation and traction

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Tributary

A smaller river which joins a larger one

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Upper course

The mountain stage of a river with steep gradients and much erosion

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V-shaped valley

A deep v-shaped valley is usually found in the upper course of the river where the water has considerable erosive power

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Velocity

The speed of the water flow

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Waterfalls

Form where the river meets a band of softer rock after flowing over an area of more resistant material. Waterfalls progressively cut back leaving a gorge

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Watershed

The highland separating one river basin from another

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Water stress

This occurs when the demand for water exceeds the available amount during a certain period or when poor quality restricts it's use

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Water table

Upper level of saturated rock/soil - top of the groundwater store

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Abrasion

An erosive process where pebbles being transported wear away bed and banks of river channel (sandpaper)

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Distributaries

Finger-like river channels which branch away from a main river channel in a delta

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Eutrophication

High nitrate levels combined with phosphate cause excessive plant and algae growth, a deteriorating process that results in loss of oxygen and the biological death of the river

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Freeze-thaw weathering

Also called frost-shattering as it occurs in cold climates when temperature are often around freezing point and where exposed rocks contain many cracks. Water enters the cracks during the warmer day and freezes during the colder night. As the water turns into ice it expands by 9% and exerts pressure on the surrounding rock, causing pieces to break off

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Floatation

A transport process whereby the lightest bit of material float along the surface

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Particle size

Range from clay (0.001mm) through silt, sand, pebbles, gravel, cobbles and boulders (500+mm)

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Physical weathering

The disintegration of rocking I smaller pieces without any chemical change in the rock; this is most likely in areas of bare rock where there is no vegetation to protect the rock from extremes of weather eg. freeze-thaw and exfoliation (or onion weathering)

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Point bar

Slip off slope

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Pot holes

Holes eroded in the solid rock of a river channel. They are drilled by pebbles caught in eddies in the river

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Soil moisture

Water held in soil layer

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Spur

A narrow neck of high land extending into a river valley, often forming the divide between two tributaries

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Time

An important factor in river erosion and deposition

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Weathering

The break-down or decomposition of rock by biological, physical or chemical processes