BISL 04-Weather and Climate

Flooded Land

When land is flooded for days or
months, the air in the soil is replaced
by water, which prevents the buildup of
oxygen, thus affecting the biological activity
of plants and the soil itself. In the latter
case, if the water does not have sufficient
salt, the incomplete decomposition of organic
matter and the significant washing away of
nutrients make the soil more acidic. If the
water contains a great deal of salt, the salt
will remain in the soil, causing a different
problem: salinization.

Torrential

rains

raise the level of

the water in the

rivers and the

riverbeds.

Little or no rain

penetrates into the

valley slopes

covered with pines.

Low-lying terrain

The main river cannot

contain the increased

flow of the tributary

rivers.

Principal

river Triverributary

Houses and

trees covered

with water

Electrical

energy can be

made available

to houses.

Agriculture is

more productive

when water can

be controlled.

Large rivers cross the

plains, which suffer

from regular flooding

Snow

increases runoff

into the rivers.

Natural

course of

the river

Hydroelectric

dam

Channeling water

via turbines also

generates

electricity.

Dam

stores water to

divert it or to

regulate its flow

outside the riverbed.

Filtering grates

prevent the passage of

unwanted objects in the

water used to produce

hydroelectric power.

Transformers

Their job is to

transform the voltage

of the electric current.

Electrical generator

Equipment that

produces electricity by

converting the

mechanical energy of

the rotating turbine

into electrical energy

Elevation

of the

reservoir

The components of the soil that
are oxidized can be reduced and
thus change their properties.

Reduction

Solid

particulates

The water

causes a decline

in oxygen in the

aerated spaces of

the soil.

The soil cannot

carry oxygen to

the roots.

Electrical

power lines

When Water Accumulates

W

ater is a vital element for life, but in excess it leads to serious consequences for people

and their economic activity. Flooding occurs when certain areas that are normally dry

are covered with water for a more or less prolonged period. The most important causes

are excessive rains, the overflow of rivers and lakes, and giant waves that wash over the coast.

Such waves can be the result of unusually high tides caused by strong surface winds or by

submarine earthquakes. Walls, dikes, dams, and embankments are used to help prevent flooding.

Floodplains

Floodplains are areas adjacent

to rivers or streams that are

subject to recurrent flooding.

EMBANKMENT
Earthen embankments help
contain rivers that tend to
overflow and temporarily
change course.

STORM

DIKES

In areas where the coast

is low and exposed to flooding,

protective dikes have been constructed

against high tides and powerful waves.

48 METEOROLOGICAL PHENOMENA WEATHER AND CLIMATE 49

Torrential

Rains

Caused by low pressure

systems, instability of

the air mass, and high

humidity

Victims of flooding in the Bay

of Bengal, Bangladesh, in 1970

250,000

Flood Control
With the construction of dikes and
embankments, the flow of rivers prone
to flooding is largely contained.

Hydroelectric

Plants

use the force and velocity of running

water to turn turbines. There are two

types: run-off-river (which uses the

natural kinetic energy of the river's

running waters) and reservoir (where the

water accumulates behind dams and is

then released under increased pressure to

the power plant).

Plants with thick,

droopy stems

There is so much

water on the

surface that the soil

cannot absorb it.