Unit 1 - Rivers -
Glossary
Definitions provided by the AS Class of
14/15
A
Antecedent soil moisture level: The degree of saturation within the soil
that has been reached before a precipitation event. DBa
B
Baseflow/groundwater flow: Water which flows
through the bedrock. DM
Bedload: The material carried
by a river by being bounced or rolled along its bed. ASh
C
Cavitation: intense erosion due to
the surface collapse of air bubbles found in rapid flows of water. PS
Cascades: Small waterfalls, typically one of several that
fall in stages down a steep rocky slope. PS
Cross profile: The cross profile of is a cross section through the river channel. It
varies from source to mouth. DBo
D
Deposition: Soil and sediments being transported by the velocity of the river are released from (dropped by) the river to form landforms such as deltas. NL
Depression storage: Is water retained in pits and depressions, for
example puddles and ponds, thus preventing it from flowing. KK
Discharge: The volume of water that passes through a certain point in the river measured in cubic metres per second (cumecs). HN
Dispersion graphs: Used to show main patterns in the distribution of
data. They show both the range of data and the distribution of each
piece of data recorded. They can be used in order to compare the distribution
between multiple sets of data. They are sometimes known as box and whisker
diagrams. DM
Drainage basin: An area of land where water
from precipitation, glaciers or ice from mountains drain via rivers
to the lowest point. The lowest point would be a larger river, a lake
or a sea. SB
E
Evapotranspiration: Water
transferred from the land to the atmosphere by evaporation from
the soil and on vegetation and transpiration by leaves. SB
F
Field capacity:
The amount of water that an area can hold before run-off begins. DBa
Flow: The movement of water through the
hydrological cycle. DM
G
H
I
Impermeable: When water cannot be absorbed. Typically used to describe surfaces/bedrock within a drainage basin. RT
Infiltration: Then process in which water moves from the ground surface into the soil by absorption, where it can either be stored or move further into the ground. HN
Inputs/outputs: These processes put in and take out
water into the water cycle. HN
Interception: When
rainwater does not reach the soil. Instead, the vegetation above the soil
catches it. SB
Inter-quartile range:
The value of the upper quartile minus the value of the lower quartile. DM
J
K
L
Lateral Erosion: Is erosion that widens the river channel,
often on the outside of a meander channel, as a result of hydraulic action,
corrasion by suspended material, or corrosion. It eventually leads to the
widening of the valley and the formation of the flood plain. DBo
Load: Material transported
by a river as bedload, suspended load or dissolved load (in solution). ASh
Long profile: A
river long profile shows the shape of the river's course
(length, height, gradient) from source to mouth. DBo
Lower course: The section of the river closest to the
mouth. Here, the river has a high volume and a large discharge. The river
channel is deep and wide and the landscape around it is flat. However, as a
river reaches the end of its journey, energy levels are low and deposition
takes place. The features here include floodplains and deltas. DBo
Lower quartile: The X value at 25% of a set of data (sometimes known as the 25th percentile) DM
M
Meander: A greatly looping bend of the
river. Over time, the loop contracts to such an extent it becomes cut off from
the river channel. This then produces an ox-bow lake. DM
Median: The
middle value in a set of data once it has been ordered chronologically. DM
Middle course: This is the middle section of the river, which may consist of meanders and oxbow Lakes. The gradient here is gentle and the river channel has widened & deepened due to lateral erosion. DBo
O
Overhang: A section of hard rock, which ‘overhangs’ a waterfall. The overhang isn’t
supported and, over time, the overhang will collapse and fall into the plunge
pool. AS
Overland flow: When water flows over the surface of the
ground due to either impermeable rock or saturated soil. In these cases, water
cannot be absorbed so it is forced to flow overland, leading to rapid
transfer. RT
P
Percolation: When
rainwater trickles through from the soil into the bedrock. Eventually, it will
get stored as groundwater storage. SB
Permeable: When water can be absorbed. Typically used
to describe surfaces/bedrock within a drainage basin. RT
Pervious: Similar to permeable in the sense that it allows
substances through. RT
Plunge pool: A concave shape formed at the bottom of the river bed, at the base of a waterfall. It is created by falling of the water scouring
(eroding) where it lands. ASi
Porous: When a substance such as water can penetrate the
small gaps between a rock, for example joints in limestone. RT
Precipitation: Any form of water that travels from the
atmosphere to the ground surface e.g snow, hail or rain. HN
Q
R
Rapids: A fast-flowing, turbulent part of a river, resulting from a steep gradient and irregularities in the rocks. ASi
River channel: the physical landform in which there is
a stream of water starts from a source and cuts through the land and meets
the sea at its mouth. HN
S
Saltation: Load bounced along
the bed, e.g. small pieces of shingle or large sand grains. Currents cannot
keep this sediment afloat for long periods. ASh
Soil moisture: Soil
moisture is the water that is held in the spaces between soil particles. KK
Soil moisture deficit: The amount of water needed to bring the
soil back to its field moisture capacity, which is the amount of watery the
soil can hold against the force of gravity. NL
Soil moisture recharge: Soil moisture recharge is the replenishment of water stores during warmer periods in the year when evapotranspiration exceeds that of precipitation. Water lost is replaced during cooler periods. DBa
Soil moisture surplus: Is when the soil has reached its full
moisture capacity and any excess water is used as runoff into the river. NL
Soil moisture utilisation: Soil moisture utilisation is when the water within
the soil is used, for example by plants. DBa
Solution: Minerals dissolved in
water and carried in solution. This load is not visible and comes from chalk or
limestone (calcium carbonate) in the banks or bed of the river. ASh
Spread- The distribution
of data on a graph e.g. wide spread. Can be used to see patterns in large
amounts of data. DM
T
Through flow: The
horizontal movement of water through the soil and towards a sea or
lake. SB
Traction: Pebbles and larger
sediment are rolled along the river bed. ASh
Transport: When rivers pick up and carry material as they flow downstream is
known as transport. There are four different types of transport process:
solution, suspension, saltation and traction. ASh
U
Upper course: This is the section of the long
profile nearest the source. The gradient here is steep and the river
channel is narrow. As the river moves through the upper
course it cuts downwards. This vertical erosion helps to create steep-sided
V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges. DBo
Upper quartile: The X value at 75% of a
set of data (sometimes known as the 75th percentile). DM
V
Vegetation: The plants in a area named as one thing. RT
Vertical erosion: Is erosion that cuts downwards. Near the source of a river there is more vertical erosion, as material is bounced and rolled along the riverbed. DBo
Velocity: The rate/speed in which the water moves along the
river at a certain point measured in metres per second (m/s). HN
W
Water budget/balance: The balance between inputs and outputs is known as
the water balance or budget. The water balance can be shown using the formula:
Precipitation (P) = stream flow (Q) +
evapotranspiration (E) +/- changes in storage (S)
P=Q+E +/- S DBa
Waterfall: A landform resulting from erosion, where section
of a river or stream flows over a steep vertical drop, often
landing in a plunge pool below. ASi
Watershed: A ridge that
separates the drainage basins of rivers flowing into different lakes or seas.
The watershed marks the highest part of a drainage basin. SB
X
Y
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