River Processes, Landforms and Flood management.

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River Processes, Landforms and Flood Management
Important terminology
Condensation: The cooling of a gas so that it changes into a liquid, for instance as water
vapour cools, it condenses to become water droplets, which, when heavy enough, fall as
rain.
Confluence: Where two rivers meet and join to form one larger river.
Delta: A build up of sediment at the point where a river meets a sea or lake, due to the
water velocity slowing and the river having less energy to carry the sediment.
Drainage Basin: The area of land drained by a river and its tributaries.
Estuary: The point at which a river begins to meet the sea. The river will be tidal, meaning
that it will have both salt water and fresh water in it.
Evaporation: Water that is warmed, usually by the sun, so that it changes into a gas (water
vapour).
Evapo-transpiration: The combination of evaporation and transpiration.
Fluvial: relating to a river, from the Latin for water.
Groundwater: see Percolation
Hydrology: The study of water
Infiltration: The downward movement of water that seeps into the soil or a porous rock.
Mouth: The end of the river, where it meets the sea, or a lake.
Overland Flow: When water flows over the surface of the ground. This occurs for a number
of reasons: the soil may be saturated and therefore be unable to absorb any more water;
the underlying rock may be impermeable or the ground may be frozen.
Percolation: The movement of water through the soil or underlying porous rock. This water
collects as groundwater.
Precipitation: Water falling to Earth in any form: e.g. rain, sleet, hail, snow, and dew, all are
encompassed by the term precipitation.
Surface Run-off: see Overland Flow
Throughflow: the movement of water with in the soil sideways, towards the river.
Transpiration: The water loss from vegetation into the atmosphere.
Tributaries: rivers running into the main one, that form part of the same drainage basin
system.
Velocity: The speed of the flow of the river.
Watershed: The imaginary dividing line between neighbouring drainage basins.

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Hydrological Cycle
Rivers are part of the hydrological cycle - a closed system which moves water from the
oceans, through the atmosphere, and back to the oceans. River systems themselves,
however, are open water-flow systems which drain an area of land. Water flows down
from higher areas to lower areas and discharges into seas or lakes.…read more

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The boundary of a drainage basin is called the watershed.
The main input into the system is precipitation, mainly as rainfall, but also as things such as
snow, sleet and hail. This water is then transferred through the system by the processes of
infiltration, percolation, overland flow and through-flow. During the course of its movement
between the sky and the river, water can also be stored in a number of places within the
system.…read more

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The course of a river
The journey of river from source to mouth is sometimes called the course of the river and
can be shown as a long profile (below). The course of a river can be divided into three main
sections: upper course, middle course and lower course.
As a river travels along its course, both the river and the landscape around it changes.…read more

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The lower course sees the river flowing at its fastest until it slows down when it meets the
sea. The channel is very wide, deep in places where the water is flowing quickest, and
smooth sided.
Upper Course (7a) Mid Course (7b) Lower Course (7c)
Long Profile Steeply sloping Shallow slopes Almost at sea level,
towards the lower towards the mouth very gently sloping
sections of the river. of the river. towards its mouth.
Cross Profile Steep sided V-shaped valley Wide, shallow valley,
v-shaped valley.…read more

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For thousands of years, rivers have been the focal point of people's activities. Some
of these are listed below:
Rivers provide a source of fresh drinking water, a source of food (fishing) and a
transport route, all of which were very important to the location of early
settlements.
Flood plains provide areas of rich, fertile alluvial soil. Hence areas like the Canterbury
plains in New Zealand are intensively farmed.
Rivers can act as a very effective power source.…read more

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Rivers have always been seen as a convenient way of waste removal. This has led to
many rivers becoming much polluted and in some cases, dangerous.
Estuaries commonly have been used for industry, which has been able to build its
factories on the flat flood plain land. This location is ideal for many industries, such
as oil refineries, as they then have easy access to the sea for transporting their
goods. The land is flat, cheap and easy to reclaim.…read more

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Rivers need energy to transport material, and levels of energy change as the river moves
from source to mouth. When energy levels are very high, large rocks and boulders can be
transported. Energy levels are usually higher near a river's source, when its course is steep
and its valley narrow. Energy levels rise even higher in times of flood. When energy levels
are low, only small particles can be transported (if any).…read more

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Large closer to base level. erosive energy of
boulders deposited Deposition occurs the river is almost
and eroded in situ. in the slower totally
moving insides of concentrated on
meanders. cutting sideways.
Much deposition
occurs.
Transportation Traction and Saltation, Mainly suspension
saltation. suspension and and solution.
solution.
River landforms
Upper-course river features include steep-sided V-shaped valleys, interlocking spurs,
rapids, waterfalls and gorges.
Middle-course river features include wider, shallower valleys, meanders, and oxbow
lakes.
Lower-course river features include wide flat-bottomed valleys, flood plains and
deltas.…read more

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As the river cuts its deep V-shaped valley in its upper course, it follows the path of the
easiest rock to erode. Thus it tends to wind its way along, leaving the more resistant areas
of rock as interlocking spurs.…read more

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