Abrasion
The bed/banks are eroded by rocks/material carried by the river which scrape against, and wear away the channel.
Antecedent Rainfall
Previous rainfall
Attrition
Reduction in size of fragments/particles within a river due to erosion, and as fragments hit each other/the bed and banks, and wear down becoming small and smooth
Braiding
If the river has a high sediment load, and low energy, the sediment is deposited, blocking the rivers route, this caused the river to continually change route.
Baseflow
Water that reaches the channel largely through slow through flow, and from permeable rock below the water table
Channel flow
The water that eventually flows out of the drainage basin
Competance
The largest size particle a river can carry
Condensation
The process by which water vapour is converted into water
Corrosion/Solution
The minerals in the rock are dissolved by the water and carried away in solution, particularly carbonates
Critical erosion velocity
The velocity needed to pick up (erode) particles of different sizes. In general the larger the particle, the higher the velocity needed to pick it up
Delta
Areas of sediment deposited at the mouth of the river when it enters a slow-moving body water (eg the sea/a lake)
Discharge
The volume of water flowing in a river per second (measured in cubic meters per second)
Drainage basin
The land area or catchment area drained by a single river and its tributaries.
Eustatic Rejuvination
Where the sea level rises or falls causing a GLOBAL change
Evaportation
The process by which liquid water is transformed into water vapoure
Evapotranspiration
The loss of warer from a drainage basin into the atmosphere from leaves of plants
Flocculation
When clay and silt particles stick together
Flood
A temporary excess of water which spills over onto land
Floodplain
Flat areas of land either side of the river channel, made from deposited silts and clays
Gradient
The slope of the land
Graded profile
Long profile of a river where erosion and deposition are in equilibrium
Groundwater flow
The slowest transfer of water in the drainage basin, through the underlying permeable rock strata
Groundwater storage
The storage of water underground in permeable rock strata
Helicoidal flow
The corkscrew flow inside a meander, responsible for moving material from the outside of one bend to the inside of the next
Hydrological cycle
The continuous movement of water between the land, sea and air
Hydraulic action
The sheer force of the moving water forces air into cracks and drags water over sediment, lifting it.
-most effective during times of high flow
Hydraulic radius
The ratio of cross sectional area of the channel and the length of its wetter perimeter
Impermeable
Not permitting the passage of fluid through the pores, interstices etc
Infiltration
The downward movement of water into soil from the surface
Interception
Prevention of precipitation from reaching the Earths surface by plants and trees
Interception storage
The total volume of water held on the surface of vegetation
Interlocking spurs
Outcrops of land which the river in the upper course must wind around as it hasn’t got the energy to erode through them. Usually accompanied by V Shaped valleys
Isostatic change/rejuvination
Changes in sea level resulting from the rise and fall of land masses
Lag time
The delay between peak rainfall and peak discharge
Lateral erosion
Erosion of width
Levées
Naturally occuring raised embankments formed when a river overflows its banks and material is deposited along the banks
Long Valley Profile
The profile of a river from source to mouth
Meander
Bends causing sinuosity within the river - typically found in the middle course
Meander scar
Formed when an oxbow lake dries up
Oxbow Lake
Horseshoe shaped lakes formed when a river erodes through the meander bend forming a new straight channel
Overland flow
The movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense for infiltration to occur
Percolation
The gravity of water within soil
Pools
Areas of deeper water with a more gentle flow, caused by difference in river energy
Pothole
Holes within the riverbed carved into rock. Turbulent, high velocity water loaded with pebbles ‘drills’ into the rock. Pebbles become trapped in the rock
Percipitation
Water in any form that falls from the atmosphere to the surface of the Earth.
Rapids
If there is a sudden change in gradient, the river becomes more turbulent and has more erosive power
Recurrence interval
The time period between floods of a particular level
Rejuvination
When there is a fall in sea level relative to the land, or a rise in land relative to the sea, this gives the river more potential energy
Relief
Shape of the land
Riffles
Areas of shallower water with fast flow, caused by difference in river energy
Sinuosity
The ‘curviness’ of the river
Soil moisture
When precipitation is greater than evapotranspirtaion, any empty pores in the soil will be filled with water
Soil storage
The total volume of water help within the soil
Surface storage
Includes water in puddles, ponds and lakes
Stem flow
The water that runs down the stems and branches of plants and trees during and after rain to reach the ground
Thalweg
The line of greatest velocity or fastest flow with the river
Surface Run off/Overground flow
The down slope flow of water over the surface
Throughflow
Water moving slowly downhill through the soil
Water table
The surface of the saturated layer of soil or rock
Transpiration
The process by which water is lost into the atmosphere from a plant through stomata
Watershed
The boundary of a drainage basin/the margin between 2 watersheds
Wetted perimeter
Length of bed and banks that is in contact with the water