Water On The Land Flashcards
Alluvium
Rock particles (clay, silt, sand, gravel) deposited by a river
Attrition
Erosive process where particles of load and knocked about as they are transported and gradually become more rounded/reduced in size
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
Bed load
Material carried by a river by being bounced or rolled along it’s bed
Channel
Course for the river water (straight or meandering)
Condensation
When water vapour changes to liquid
Confluence
Point at which 2 or more rivers meet
Cross profile
Shape of a slice across a river
Deforestation
Removal of a forest/stand of trees where land is thereafter converted to a non-forest use
Delta
River mouth choked with sediment causing the main channel to split into smaller branching channels or distributaries
Depth
Measurement of the distance between the bed of the river and surface. Increases downstream (joined by lots of tributaries)
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)
Drainage basin
Land that is drained by a river and it’s tributaries enclosed by the watershed
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
Erosion
Wearing away of bed and banks of river channel by abrasion, hydraulic action, solution and attrition
Estuary
The tidal mouth of a river with large flat expanses of mud exposed at low tide
Evaporation
Water lost from the ground/vegetation surface
Flood plain
Wide, flat floor of a river valley. It consists of fertile sediments (alluvium) deposited by the river during flood conditions
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
Gorge
Steep-sided narrow rocky valley marking the retreat of a waterfall
Gradient
Slope of river profile, steep close to the source, gradually becoming more gentle until the river reaches sea level
Groundwater
Water stored in rock beneath the surface
Groundwater flow
Water flowing through the rock layer parallel to the surface
‘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)
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
Infiltration
Water sinking into soil from the ground surface
Interception
Water being prevented from reaching the ground by trees or other vegetation. A store of water
Interlocking spurs
As the river descends from the highland it begins to meander between spurs which interlock down the valley
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
Levées
River embankments built by deposition as the river floods (natural or man-made)
Load
The material transported by a river as bedload, suspended load or dissolved load (in solution)
Long profile
A slice through the river from source to mouth
Lower course
The section of the river near the sea, where deposition is the most important process and the valley becomes wider and flatter
Meander
A bend in the river. The outside of the meander has the fastest flow and deepest water
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
Mouth
Where a river ends, at a lake or the sea
Oxbow lake
A meander which has been cut off from the main river channel and abandoned
Peak discharge
Maximum discharge in a river
Peak rainfall
Time period on a flood hydrograph when the most rain fell
Percolation
Water seeking deeper below the surface, often from the soil into the bedrock
Pervious
A soil which allows relatively free movement of water
Plunge pool
Deep pool below a waterfall
Precipitation
Any source of moisture reaching the ground eg. snow, rain, frost
Profile
The cross-section of the river from it’s source to it’s mouth concave in shape
Rapids
Found where the river meets a band of resistant rock and usually precede a waterfall
River cliff
Steep sided slope, created on the outside of a meander bend by the erosive effect of fast-flowing water
Saltation
A process of transport; material bounced along the bed of the river
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)
Slip-off slope
Forms on the inside of a meander bend as a result of deposition in the slower flowing water
‘Soft’ options
Flood protection that is more ecologically sensitive
Solution
Some rocks such as limestone are subject to chemical attack and slowly dissolve in the water
Source
Where a river starts, usually in the mountains
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’
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
Surface run-off (overland flow)
Water flowing on top of the ground
Surface storage
Water held on the ground surface eg. puddles/ponds
Suspended load
Very small and light material, usually find clay and silt, transported by the river suspension
Throughflow
Water flowing through the soil layer parallel to the surface
Traction
Material rolled along the bed of the river
Transpiration
Water lost through pores in vegetation
Transportation
The river moves material as bedload, suspended load or dissolved load (in solution). Bedload can be moved by saltation and traction
Tributary
A smaller river which joins a larger one
Upper course
The mountain stage of a river with steep gradients and much erosion
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
Velocity
The speed of the water flow
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
Watershed
The highland separating one river basin from another
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
Water table
Upper level of saturated rock/soil - top of the groundwater store
Abrasion
An erosive process where pebbles being transported wear away bed and banks of river channel (sandpaper)
Distributaries
Finger-like river channels which branch away from a main river channel in a delta
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
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
Floatation
A transport process whereby the lightest bit of material float along the surface
Particle size
Range from clay (0.001mm) through silt, sand, pebbles, gravel, cobbles and boulders (500+mm)
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)
Point bar
Slip off slope
Pot holes
Holes eroded in the solid rock of a river channel. They are drilled by pebbles caught in eddies in the river
Soil moisture
Water held in soil layer
Spur
A narrow neck of high land extending into a river valley, often forming the divide between two tributaries
Time
An important factor in river erosion and deposition
Weathering
The break-down or decomposition of rock by biological, physical or chemical processes
