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Geography Rivers - Rejuvenation
- Where does rejuvenation occur?
- Rejuvenation occurs when their is either a fall in sea level relative to the
level of the land or a rise of the land relative to the sea. This enable a river
to renew its capacity to erode as its potential energy is increase. The river
adjusts to its new base love, at first in its lower reaches and then
progressively inland. In doing so, a number of landforms may be created:
knick points, waterfalls and rapids, river terraces and incised meanders
- Rejuvenation occurs when their is either a fall in sea level relative to the
level of the land or a rise of the land relative to the sea. This enable a river
to renew its capacity to erode as its potential energy is increase. The river
adjusts to its new base love, at first in its lower reaches and then
progressively inland. In doing so, a number of landforms may be created:
knick points, waterfalls and rapids, river terraces and incised meanders
- Knick points
- A knick point is a sudden break or irregularity in the gradient along the long
profile of a river. Some knick points are sharply defined, for example waterfalls,
where as other are barely noticeable. Although a number of factors can cause
such features to occur, they are most commonly attributed to a rejuvenation.
When a river is rejuvenated, adjustment to the new base level starts at the sea
and gradually works its way up the course of the river. The river gain renewed
cutting power (in the forms of vertical erosion), which encourages it to adjust
its long profile. In this sense the knick point is where the old long profile join
the new long profile. The knick point recedes upstream at a rate which is
dependent on the resistance of the rocks, and may linger at a relatively hard
outcrop. It can be difficult to determine whether a waterfall occurs due to
variability in a rock type or to rejuvenation. Headward erosion upstream may
mean that a waterfall cuts back through the vally towards
- Knick point: Usually marked by rapids, this
represents rejuvenation and is a sudden
break in the long profile of the river
- A knick point is a sudden break or irregularity in the gradient along the long
profile of a river. Some knick points are sharply defined, for example waterfalls,
where as other are barely noticeable. Although a number of factors can cause
such features to occur, they are most commonly attributed to a rejuvenation.
When a river is rejuvenated, adjustment to the new base level starts at the sea
and gradually works its way up the course of the river. The river gain renewed
cutting power (in the forms of vertical erosion), which encourages it to adjust
its long profile. In this sense the knick point is where the old long profile join
the new long profile. The knick point recedes upstream at a rate which is
dependent on the resistance of the rocks, and may linger at a relatively hard
outcrop. It can be difficult to determine whether a waterfall occurs due to
variability in a rock type or to rejuvenation. Headward erosion upstream may
mean that a waterfall cuts back through the vally towards
- River terraces
- A river terrace is a remnant of a former floodplain, which has ben left
at a higher level after rejuvenation of the river. Where a river renews
its downcutting, its stinks its new channel into the former floodplain,
leaving the old floodplain above the level of the present river. The
terraces are cut back as the new valley is widened by lateral erosion. If
renewed rejuvenation takes place, the process is repeated and anew
pair of terraces is formed beneath the original ones. The River Thames
has created terraces in its lower course by several stages of
rejuvenation. Terraces provide useful shelter from floods in a
lower-course river valley, and natural rhouteways for roads and
railways. The built-up areas of Oxford and London are mainly located
along the terraces of the River Thames.
- River terrace: A narrow, flat piece of ground
that runs parallel to the river on either side,
above the level of the floodplain. The are
usually created following a fall in base level.
- A river terrace is a remnant of a former floodplain, which has ben left
at a higher level after rejuvenation of the river. Where a river renews
its downcutting, its stinks its new channel into the former floodplain,
leaving the old floodplain above the level of the present river. The
terraces are cut back as the new valley is widened by lateral erosion. If
renewed rejuvenation takes place, the process is repeated and anew
pair of terraces is formed beneath the original ones. The River Thames
has created terraces in its lower course by several stages of
rejuvenation. Terraces provide useful shelter from floods in a
lower-course river valley, and natural rhouteways for roads and
railways. The built-up areas of Oxford and London are mainly located
along the terraces of the River Thames.
- Incised meanders
- If a rejuvenated river occupies a valley with well-developed meanders, renewed energy results in them becoming incised or
depended. Incised streams and rivers have cut deeply into the landscape in many parts of the British Isles. The nature of the
landforms created is largely a result of the rate at which vertical erosion has taken place. When incision is slow and lateral erosion is
occurring, an ingrown meander may be produced. The valley becomes asymmetrical, with steep cliffs on the outer bends and more
gentle slip-off slopes on the inner bends. With rapid incision, where downcutting or vertical erosion dominates, the valley is more
symmetrical, with steep sides and a gorge-like appearance. These are described as entrenched meander
- Incised meander: This is caused by rejuvenation. it is a meander
that has cut deeply into the floodplain, creating steep cliff-like
banks
- If a rejuvenated river occupies a valley with well-developed meanders, renewed energy results in them becoming incised or
depended. Incised streams and rivers have cut deeply into the landscape in many parts of the British Isles. The nature of the
landforms created is largely a result of the rate at which vertical erosion has taken place. When incision is slow and lateral erosion is
occurring, an ingrown meander may be produced. The valley becomes asymmetrical, with steep cliffs on the outer bends and more
gentle slip-off slopes on the inner bends. With rapid incision, where downcutting or vertical erosion dominates, the valley is more
symmetrical, with steep sides and a gorge-like appearance. These are described as entrenched meander
- What is rejuvenation?
- An increase in the energy of a river caused by either a
fall in its base level or an uplift of the land
- An increase in the energy of a river caused by either a
fall in its base level or an uplift of the land
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