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­ RIVERS,
FLOODS
AND MANAGEMENT
DRAINAGE BASINS:
It is an area surrounding the river where the rain falling on the land flows into that river (catchment).
The boundary of a drainage basin is the watershed ­ any precipitation that falls beyond the water shed
enters a different basin.…read more

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WATER BALANCE BUDGET:
Water balance is worked out from inputs and
outputs; it affects how much water is stored in the basin.
1. In wet seasons, precipitation exceeds
evapotranspiration. This creates a water surplus. The
ground stores fill with water so there's more surface runoff
and higher discharge, so river levels rise.
2. In drier seasons, precipitation is lower than
evapotranspiration. Ground stores are depleted as some
water is used and some flows into the river channel, but
isn't replaced by precipitation.
3.…read more

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SOIL TYPE AFFECTS LAG TIME AND PEAK DISCHARGE
Sandy soils = lots of infiltration. Clay soils = low infiltration rates = increase surface runoff, reduces lag time
and increases peak discharge.
5) VEGETATION AFFECTS LAG TIME AND PEAK DISCHARGE
Makes Vegetation = interception and slows its movement to river channel = increases lag time.
Interception = highest when lots of vegetation and deciduous trees have their leaves.
More vegetation = greater water loss before reaching river channel reducing peak discharge.…read more

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When the river is forced to slow down (e.g. before a narrow section of a channel) it loses energy.
· Energy is lost when the river meets the sea.
· The capacity is the total load that a river can transport at a given point.
· The competence describes the maximum particle size that a river is capable of transporting at a given point.…read more

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At the mouth of a river: little gravitational potential energy, but lots of kinetic energy.
CHANNEL CHARACTERISTICS AFFECT VELOCITY AND DISCHARGE:
Velocity and discharge of river increases further downstream.
Discharge increases as tributaries and more surface runoff join the main channel.
River velocity influenced by gradient, discharge and channel characteristics ­ the shape and
roughness.
1) Most of a river's kinetic energy is used to overcome friction ­ the rest causes erosion.…read more

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As the hard rock is undercut, it can collapse. A deep plunge pool is carved out by abrasion at the
foot of the waterfall as the bits of collapsed rock are swirled around b turbulence.
4) Overtime, more undercutting causes more collapse. The waterfall will retreat leaving behind a steep
sided gorge.…read more

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BRAIDING
WHAT IS A BRAIDED CHANNEL?
- A braided channel is the name given to a single stream in a braided river network. They are formed when islands
(which are often temporary) of sediment build up in the river and
split the water into lots of smaller streams that will make up a
network of channels.
- A braided channel is also called an eyot.
- Braided streams occur in rivers with high slope and/or
large sediment load.…read more

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WHAT IS A DELTA?
- A landform produced by the deposition of sediment at
the mouth of a river as it enters a sea or lake. Deposition
occurs as the river's velocity and
sediment-carrying capacity decrease as it enters the lake
or sea, and bedload and suspended material are
dumped. In addition, clay particles flocculate due to the
chemical change in sea water and settle on the bed.
Deltas form where the rate of deposition exceeds the
rate of sediment removal.…read more

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These are described as intrenched meanders.
Where incision is due to a relative fall in sea level, giving rejuvenation along the river course, knick points and river
terraces will also be formed.
~~~~~~~~~~~~~~~~~~~~~~~~~
CAUSES AND IMPACTS OF FLOODING:
· The main causes of flooding are prolonged and heavy rainfall.
1) Flooding occurs when the discharge of a river is so high that the river spills over its bank onto the
floodplain.…read more

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Georgia

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Reorran

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