Option A: Freshwater- 1.1 Drainage Basin Hydrology and Geo...
Study
Option A: Freshwater- 1.1 Drainage Basin Hydrology
and Geomorphology
Terms in this set (90)
An area of land that is drained by a river and its
tributaries. The highest land forms a natural
dividing line between drainage basins.
Drainage Basin
Area of land within which water is collected in a
drainage basin.
Catchment
Source
Point at which a river starts, usually high in the hills
in V shaped valleys.
Point at which a river ends. This is right out on the
coast. At this point, the river is slow filling wide
and is surrounded by a flat river valley.
Mouth
A stream
or river
which flows
intoGeo...
a mainstream
(or
Study
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and
parent) river and which does not flow directly into
that sea.
Tributary
Meeting of two or more bodies of water. Usually
refers to the point where a tributary joins a more
major river, called the mainstream.
Confluence
The line separates drainage basins. It runs along a
geographical barrier between drainage basins
such as a ridge, hill or mountain. Other terms used
to describe this are: Catchment area, catchment
Water Shed
basin, drainage area, river basin & water basin.
The section of the river near the mouth that is
tidal.
Estuary
A wide
straight
or waterwayand
between
two
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
Geo...
Study
landmasses that lie close to each other.
Channel
A bend in a river channel that occurs on flat land
where the river is large and established.
Meanders
What is a system?
Open Systems
A set of interrelated parts.
A system where water/energy/matter can be
added or lost and pass across boundaries.
Has a range of inputs, outputs, stores, transfers
and flows.
Has stores such as lakes, rivers, cryosphere (ice),
Open System Example:
Drainage Basin
aquifers, vegetation.
Energy from the sun (solar) and precipitation
(including rain & snow) enter the system and
waters leave it.
Flow includes movement of water such as
infiltration & through flow.
Energy but not mass passes across system
Closed System
boundary e.g. Water Cycle
The Earth
WhenBasin
water and
other things
are Geo...
added to the
Study
Option A: Freshwater- 1.1 Drainage
Hydrology
and
system.
Examples:
Input Definition and Examples
Water
Energy
Rocks
Sediment material
When water is moving in the system.
Processes/Transfers Definition
and Examples
Examples:
Erosion
Transportation
Deposition
When water is stationary in the system.
Examples:
Stores Definition and
Lakes
Examples
Aquifers
Groundwater
Dams
When water leaves a system.
Outputs Definition and
Examples
Examples:
Water
Energy
Sediment
Processes at work within a
Drainage Basin: Precipitation
(Input)
Any moisture that falls from the sky.
Examples:
Rain
Snow
Processes at work within a
When water travels from unsaturated ground into
Drainage Basin: Percolation
saturated ground.
(Transfer)
Study
ProcessesA:
at Freshwaterwork within a 1.1 Drainage
The movement
of water through
Option
Basin Hydrology
and saturated
Geo... ground.
Drainage Basin: Groundwater
Flow (Transfer)
Processes at work within a
Water that is travelling in river or streams.
Drainage Basin: Channel Flow
(Transfer)
Processes at work within a
When water travels across the surface of the
Drainage Basin: Surface Run
earth.
off (Transfer)
Processes at work within a
When intercepted water than travels down the
Drainage Basin: Stem Flow
branches and trunks of vegetation.
(Transfer)
Processes at work within a
The movement of water through unsaturated
Drainage Basin: Throughflow
ground.
(Transfer)
Processes at work within a
When water travels from the surface of the earth
Drainage Basin: Infiltration
into the ground beneath.
(Transfer)
Processes at work within a
Intercepted water dripping off vegetation onto
Drainage Basin: Canopy Drip
the ground.
(Transfer/Store/Output)
Processes at work within a
Any water that is held on the surface of the earth
Drainage Basin: Surface
e.g Lake or pond.
Storage (Store)
Some surface stores
Processes at work within a
Water that is stored in saturated ground.
Drainage Basin: Groundwater
Storage (Store)
ProcessesA:
at Freshwaterwork within a 1.1 Drainage
WaterBasin
that is Hydrology
stored below the
surface
in
Option
and
Geo...
Drainage Basin: Soil-moisture
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unsaturated ground.
storage (Store)
Processes at work within a
When an object (building, tree) stops precipitation
Drainage Basin: Interception
reaching the ground beneath.
(Store)
Processes at work within a
Part of the earth's water that are frozen e.g.
Drainage Basin: Cryosphere
Glaciers, permafrost, ice sheets, lake ice and snow
(Store)
cover
Processes at work within a
Liquid water from surface stores and rivers turning
Drainage Basin: Evaporation
into water vapour (gas).
(Output)
Processes at work within a
Eventually most rivers enter the sea and discharge
Drainage Basin: River
the river's flow into the sea.
discharge (Output)
Processes at work within a
Liquid water evaporating from vegetation.
Drainage Basin: Transpiration
(Output)
When precipitation meets the ground it begins a
journey down towards a river sea.
Can travel in a number of different ways such as
infiltration, percolation, surface run off, through
The Water Cycle
flow, groundwater flow.
RiversBasin
createHydrology
their own valleys,
factors
Option A: Freshwater- 1.1 Drainage
andother
Geo...
River Systems
Study
influence the processes and
landforms/characteristics that are created.
Geology of the area
- Different rocks erode at different rates.
- Will influence the speed of development of
landforms and the type of landforms that develop.
- Water penetration into and movement through
Factors influencing the
the soil will be influenced by soil type.
processes and landforms
Climate of an area
- Amount and timing of rainfall is very influential in
determining river flow while temperature can
influence evaporation
Number of tributaries
Amount and type of human activity in the valley
Bank
Wetted Perimeter
The sides of the river channel
The total length of the bed and the banks in
contact with the river.
The width of the river multiplied by the depth of
Cross-sectional area
the river.
An average depth reading is normally taken.
The cross sectional area is normally given in m2.
The speed that the water in a river is travelling at.
Stream Velocity
Unit of measurement = metres a second (m/s).
Measured using a flowmeter or by timing a
floating object over a set distance.
The amount of water in a river at a given point.
Discharge
Measured in cumecs (cubic metres a second).
Calculated by multiplying the cross-sectional area
by the velocity.
The ratio
between
area of the
cross
section ofStudy
a
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and
Geo...
Hydraulic Radius
Load Quantity
Channel Depth
Occupied channel width
channel and the length of its perimeter.
Total load of all sizes.
The height from the water surface to the channel
bed.
Distance across the actual channel, measured at
the water surface.
A horizontal movement of water.
Very rarely found in rivers.
The flow travels over sediment on the river bed
Types of Flow: Laminar
without disturbing it.
Consists of a series of erratic eddies, both vertical
and horizontal in a downstream direction.
Types of Flow: Turbulent
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Larger
hydraulic
radius = smaller
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and amount
Geo... of water
in the cross section in contact with the perimeter.
Less friction reduces energy loss and greater
velocity.
Smaller hydraulic radius = larger amounts of water
Influences on River Velocity:
Channel Shape in Cross
Section
in contact with the wetted perimeter.
Greater friction increases energy loss and
reduced velocity.
Shape of the cross section controls point of max
velocity in the channel.
Point of max velocity is different in a river with a
straight course where channel is approximately
symmetrical compared with a meandering channel
where the shape is asymmetrical.
Influences on River Velocity:
As bank and bed roughness increase, so does
Roughness of channel's bed
turbulence therefore mountain stream can pick up
and banks
loose material and carry it downstream.
Discharge, channel cross section area and
hydraulic radius all increase with more water from
tributaries, throughflow and ground flow.
Less energy will be lost through friction and the
erosive power of bedload material will decrease.
Influences on River Velocity:
Channel slope
The river flows over a gradually decreasing
gradient as a result.
The upper part has the most turbulence,
roughness and bedload in comparison to
discharge friction whereas the lower part of the
river has the greatest discharge, greatest velocity,
highest average hydraulic radius, and the greatest
cross-sectional area.
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If velocity
is high,
the amount
of energy
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and
Geo...available
after friction has been overcome will be greater
Relationship between Velocity
and Turbulence
and so turbulence increases.
If velocity is low, there is less energy to overcome
friction. Turbulence decreases and may not be
visible to the human eye.
Role played by Friction in
Flow of Water
More friction within a river = slower velocity.
When stream channel is semicircular, there is less
friction = faster velocity.
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Discharge-Due to
input
from a greater
Option A: Freshwater- 1.1 Drainage
BasinIncreases
Hydrology
and
Geo...
amount of the drainage basin above the point of
measurement
Occupied channel width- Increases- Due to
discharge, input from tributaries etc.
Channel Depth - Increase downstream as does
the discharge of the river.
Average velocity - Steady increase downstream. River becomes more efficient downstream with
proportionally less contact with its bed and banks.
Shown by higher hydraulic radius and lower
channel bed roughness.
The Bradshaw Model
Load Quantity- Increases with discharge and
velocity.
Load particle size - Decreases considerably
downstream - Angular pebbles become more
rounded = Erosional process of attrition.
Channel Bed Roughness - Decreases- Fewer
stones etc, smaller load particle size etc.
Slope angle (Gradient) - Decreases
Geological
the basin E.g.
Study
Option A: Freshwater- 1.1 Drainage
Basinstructure/lithology
Hydrology andofGeo...
Hard rocks erode slowly causing waterfalls and
rapids
Variations in the bed load E.g. When a tributary
with a coarse load may lead to the steeping of the
gradient of the main valley.
The Long Profile and Factors
affecting it
Sea level changes.
Human impact E.g. In the Werribee basin, the
building of a dam has changed the long profile
half way along the river's course.
Processes by which rock, sand and soil are broken
down and carried away
Erosion
Erosional Process: Hydraulic
Caused by the force of moving water
action
undercutting a river's banks
Occurs when sand, stones and rocks are dragged
along the river bed, wearing away other
Erosional Process:
fragments and mineral grains
Abrasion/Corrasion
Turbulence in the river bed can also dislodge
stones and rocks which 'drill' into the bed, causing
erosion to both the bed and the rocks
Occurs when rocks being carried along by the
Erosional Process: Attrition
river smash against the river's bed and banks
causing them to break into smaller particles.
They also become smoother and more rounder
Occurs
whenHydrology
small particlesand
of material
Option A: Freshwater- 1.1 Drainage
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Geo...are
Erosional Process: Corrosion
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dissolved in weak acidic water
Occurs mainly in steep rocky upland areas.
Erosional Process: Vertical
Geology of the river bed will affect the speed at
Erosion
which this occurs.
Greatest in Upper course
Erosional Process: Lateral
erosion
Occurs mainly where the river gradient is less.
Strength of the bed and banks will affect the rate
of erosion.
The smallest particles in the river are dissolved
into the water, carried in solution.
Slightly larger material changes, it is suspended
and carried along in suspension.
Transportation
Transportation Processes:
The cloudier the river, the more sediment it is
carrying in suspension.
Soluble chemicals are dissolved in water
Solution
Transportation Processes:
Fine silt or clay particles carried along in the water
Suspension
Transportation Processes:
Saltation
Sand, stones and rocks are temporarily picked up,
moved and then dropped again, involving them in
a 'skipping' movement along the river bed.
Transportation Processes:
Material is dragged along the bed. This material is
Traction
known as the 'bed load' of a river
Definition
= The
process in which
water, ice, wind,
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Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and Geo...
and gravity drop newly formed sediments.
River flow varies over time and along its length as
the slope varies, due to the inputs and outputs of
Deposition
water.
As it loses energy, the amount and size of the
material a river can move decreases, deposition
can occur.
Sediment Supply Zone
Transfer Zone - Sediment moved by the river
though it may be stored temporarily in a flood
Zones of a river
plain.
Deposition Zone - Where material is deposited.
This may be as a delta or other deposits in a lake
or at the coast.
Channel Characteristics of a
River's Course: Upper Course
Channel Characteristics of a
River's Course: Middle Course
Steep V shaped Valley
Narrow/Shallow Channel
High Bed Load
Open/ Gentle sloping valley with flood plains.
Wider/deeper channel.
More Suspended sediment.
Open/gentle sloping valley with floodplain
Channel Characteristics of a
Flat & Wide Floodplain.
River's Course: Lower Course
Wide, open valley.
Very wide and very deep channel.
Seasonality & Fluvial
Processes
Rainfall/Flooding varies through the years
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Occurs
because
vertical erosion
dominant as
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and isGeo...
water flows down the steepest gradient of the
Upper Course Landforms:
rivers course.
Deep narrow valley (often v
shaped)
A projection or ridge of land that curves down
into a valley.
Upper Course Landforms:
Interlocking spurs
If a river bed is uneven, fast flowing water swirls,
and stones and rocks carried by this swirling water
can cut circular depressions into the river bed.
These gradually deepen to form potholes. Larger
Upper Course Landforms:
but similar depressions or holes form at the base
Potholes
of a waterfall and are known as plunge pools.
Caused
by the
differences in
the hardness
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
and
Geo... of Study
rocks over which the river is flowing and cutting
into.
When a layer of hard rock (which resists erosion)
lies across a river's course, the soft rocks
downstream are eroded more quickly than the
Upper Course Landforms:
Waterfalls
hard rock.
The river bed is then steepened when it crosses
the hard rock and a waterfall can develop.
An area of broken, fast flowing water where the
slope of the bed increases but it isn't steep
enough to produce a waterfall.
Can also develop when a waterfall retreats up
Upper Course Landforms:
stream. A further way rapids are developed is
Rapids
when a hard rock layer dips downstream.
Gorges are narrow valleys with steep sides.
They form when a waterfall retreats upstream in
an area of erosion resistant rock, or where a river
maintains its course and erosional capacity when
Upper Course Landforms:
the parts of the region in which its flows are
Gorges
uplifted.
Canyons
differ
from gorgesand
as their
sides are Study
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
Geo...
steeped, caused by alternate layers of hard and
Upper Course Landforms:
soft rock.
Canyons
The gradient is gentler in the middle course than
in the upper course of a river and erosion occurs
both vertically and laterally.
Middle Course Landforms:
Wider valley with an open U
shape in the cross section
Spurs removed through lateral erosion creating a
wider valley floor. Weathering also lowers the
valley sides.
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Meanders
develop
becauseand
water
flowing around
Option A: Freshwater- 1.1 Drainage
Basin
Hydrology
Geo...
bends moves at different speeds. This leads to
erosion on some banks and deposition on other
banks.
The river flow is fastest on the outside of a band
(known as the concave bank) and slowest on the
inside of a bend (known as a convex bank).
The movement of water around a bend isn't just
downstream. Water also sinks in the outside of the
bend and then moves across the river bed as it
slows down. The combination of the two
Middle Course Landforms:
movements causes the 'corkscrew' around the
Meanders
bed.
Concave bank (outside of bend) is eroded and
deposition occurs on the convex bank (inside of
the bend). Erosion is concentrated on the
downstream side of the concave bank which
means that over time, the meander will
move/migrate downstream.
Spurs are removed by lateral erosion and their
remains may form a line of bluffs on each side of
the valley floor.
Middle Course Landforms:
Wide Valley floor
Lateral erosion and the downstream migration of a
river bends straightens the valley and widens its
floor.
As a valley floor widens, it starts to form into a
floodplain which is a characteristic of the third
section of a river.
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Lower Course
Landforms:
The gradient
is very gentle and
river velocity
Option
A: Freshwater1.1 Drainage
Basin Hydrology
andthe
Geo...
Wide relatively flat
decreases. The river begins to overflow its banks
floodplains
and deposits fine silt and mud on the valley floor.
Some of the river's load is deposited on its bed.
Lower Course Landforms:
Braiding of the river channel
When this occurs mounds can form leading to the
development of islands or bars. The river is then
divided into several channels. When this happens,
the river is said to be braided.
Meanders become more pronounced as they
curve across the wide valley floor, and cut offs,
Lower Course Landforms: Ox
called ox bow lakes, can be produced.
box lakes
Deposition occurs along the banks of the lower
course of a river when it's in flood.
These banks gradually get higher and are called
Lower Course Landforms:
Levees
natural levees.
Study
WhenBasin
a riverHydrology
enters one of these
bodies of still
Option A: Freshwater- 1.1 Drainage
and Geo...
water its forward movement ceases and it cannot
support its load. This accumulation of river load is
called an alluvial deposit.
These deposits can clog up the river's exits
causing it to develop new channels. The river will
then break through some blockages of alluvium,
cutting new channels and spreading its load in
new directions.
Lower Course Landforms:
Alluvial deposits or deltas
Where material does build up at the mouth of a
river, it will gradually form a fan shaped or
triangular alluvial deposit called a delta. If rivers
fill in shallow parts of the sea over a long period
of time, they can create large areas of alluvium
called alliuvial plains.
A fall in sea level or a rise in land level will result in
the river cutting into its alluvial deposits, creating
a new flood plain at a lower level and leaving river
Lower Course Landforms:
River terraces
terraces where the floodplain used to be.