GEO Brasil - UNEP

The dry season, as a disaster, is related
to the intense fall of surface water
reserves and the consequences of
such fall on river flows and agricultural
/ cattle-ranching productivity
Although the dry seasons occur more
frequently in tropical regions, no area
of agricultural and cattle-ranching
production can be considered totally
immune from the event In Brazil, dry
seasons occur frequently in the
Northeast, Southeast, MidWest and
South regions
way; it keeps in a flood situation during some time and then flows gradually
Usually, gradual inundation is cyclic and notably seasonal
A typical example of periodicity occurs in the annual inundations in the Amazon
river basin During almost one hundred years of observation and records, it was
characterised that the flood crest occurs in mid-June in most years in the city of
Manaus
Gradual inundations are intensified by medium and long term meteorological
variables, and are little subject to influence by weather daily variations; they are
more related to long periods of continuous rain than to intense and concentrated
rain The event is characterised by its coverage and large extension
the state of the environment in Brazil
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Floods
The increase of surface discharges
can be caused by a number of
immediate and/or concurrent factors
In Brazil, most of times, it is caused
by intense rainfall, occasioning floods
of rivers, lakes, channels and dammed
areas
Due to the extension of the Brazilian
territory, which is exposed to several
climate-related factors associated to
a water basin network with over 55,457
kilometres of rivers, the floods occur
in all Brazilian regions, in different
periods of the year The following types
can be highlighted: floods or gradual
inundation; flash floods or sudden
inundation; overflows
Gradual inundation is characteristics
of large water basins and plains rivers,
such as the Amazon River, the
Paraguay River, the Nile and the
Mississipi-Missouri River The event
evolves in an easily predictable way,
and the flood wave develops slowly
from upstream to downstream,
between regular intervals The water
level rise in a gradual and predictable
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