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Summary IEB - Grade 12 - Geography notes - Geomorphology
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In-depth grade 12 geography notes covering grade 12 geomorphology (Fluvial Landforms, RIVERS). IEB syllabus.
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,Geomorphology iDrainage Systems ·
Important terminology :
drainage basins
basins-
- an area of land where all flowing surface water converges to a single point.
catchment area - the area over which rain falls and is caught by a drainage basin.
catchment area -
river system - a main river with all its tributaries.
river -
watershed
watershed-
- an area of high ground separating two drainage basins.
tributary - a river that joins another larger river.
-
river mouth
river mouth-
- sea or lake where the river ends.
source - where the river begins.
source-
confluence
confluence
- the place where two rivers join.
water table - the upper level of underground saturated rock.
water table
-
surface run-off - the surface flow of water.
surface run-off-
groundwater
groundwatrate - water found under the ground.
interfluve - high-lying area or spurs between two river valleys.
infiltration
infiltration - movement of water through soil into the ground.
-
base flow - the base flow of the river represents the normal day to day discharge of the river and is the
base flow-
consequence of groundwater seeping into the river channel.
#
Factors affecting Surface Run-off and Infiltration P4LGS
W
as water flows over the surface, infiltration into the soil will occur.
this water will eventually seep into the groundwater and will contribute to the base flow of a river.
San
surface run-off infiltration
precipitation
moisture/ rain. slow, gentle rain. large amount of rain, hard.
porosity
water can filter in air spaces. porous. non-porous.
permeability
water passes through. permeable. impermeable.
plants (vegetation). more vegetation. less vegetation.
landuse
agri/ tar/ grass. grass/ agriculture. tar and concrete surfaces.
gradient
steepness. gentle slope. steep slope.
saturation
air space available. less saturated soil. more saturated soil.
Types of Rivers i
permanent rivers :
flow all year round.
↳
it receives a constant supply of rainwater.
·
a permanent river need not necessarily have a constant volume of water in it throughout the year.
·
but it must always have water in it.
D
found on the south and east coasts of South Africa.
,
always has base flow as even the dry season water table is above the river bed. (water table)
·
, Geomorphology
:
Drainage Systems
Types of Rivers
periodic rivers
flow only during wet seasons.
water table lies above the bed in the rainy season and below during the dry seasons.
found on plateau of South Africa.
dry season water table is below the river bed. (water table)
I
episodic rivers
.
flow only during times of heavy rainfall.
·
seasonal flow.
·
a heavy rainstorm will make them flow, or even flood, but the water flows away within hours.
·
surface water may not be seen in them for months or years.
~
found in dry western parts of South Africa.
.
wet season water table is also below the riverbed. (water table)
-
exotic river
: flow in an arid region.
this is because the river is well supplied with water from its very wet upper reaches.
rivers that exhibit the flow pattern of the wet areas of their upper reaches
:
and not that the desert regions through which they flow later.
Transportation In a River
:
at any one time within a river channel, there is at least one of three processes taking place
weathering
the breakdown of the earths crust by the weather, rain snow, wind and ice.
process in which rock is broken down into smaller pieces or smaller rock.
no movement is involved with weathering.
particles are worn away.
erosion
process in which earthen materials are worn away and transported by natural forces such as wind or water.
transporting weathered materials.
moving agents are - wind, water, ice.
these agents pick up the materials which has been formed from weathering.
the materials carried is known as its load.
deposition
when the load of the agents either - stops moving, drops, deposits its load.
because the load is to large and there is not enough energy
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