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Key Ideas - Rivers |
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Upper Course |
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| Erosion is the main process operating in the upper course of a river. | ||
| The direction of erosion is vertical. | ||
 There are
four
main types of erosion – hydraulic action, attrition,
abrasion and corrosion. |
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Valleys are
v-shaped
with
interlocking
spurs.
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| Waterfalls are formed where a river meets a band of less resistant rock. Plunge pools and gorges are features associated with the formation of waterfalls. | ||
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Rapids
are smaller
scale features formed where finer bands of varying resistance of
rock are found.
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Middle and Lower Course |
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Processes of
erosion,
transport
and
deposition
operate to create the landforms of the middle and lower course of a
river. |
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There are four types of transport:
traction,
saltation,
suspension
and
solution.
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The main direction of erosion is
lateral.
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Erosion and deposition contribute to the formation of
meanders
and
ox-bow lakes.
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Deposition is the main process contributing to the formation of
flood plains,
leveés
and
deltas. |
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Drainage Basin |
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| A drainage basin is an area of land drained by a main river and its tributaries. | ||
| The hydrological (water) cycle is the global circulation of water. It is a closed system. | ||
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A drainage basin system is one part of the hydrological cycle.
It is
an
open
system as it has
inputs
and
outputs.
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Floods |
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A
flood hydrograph
shows how a river’s
discharge
changes in response to a rainfall event. |
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The shape of a flood hydrograph is influenced by a range of
physical
and
human
factors. |
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A river floods when it exceeds its
bankfull
discharge.
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Flooding
can be a result of both
physical
and
human
factors. |
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Physical factors include
climatic
conditions and
drainage basin characteristics. |
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The
effects of flooding are
short-term and
long-term.
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Flood management schemes can aim to
prevent
flooding or
reduce its impact. |
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Flood management schemes can have both positive and
negative
effects.
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