chapter - Atmospheric and Oceanic Science

The main services and problems of water resource
Floods are not events as dramatic as hurricanes or earthquakes, but they are the
most lethal phenomena since, before the Indic Ocean tsunami, 40% of the victims
of disasters are produced by them. They result in humanitarian catastrophes
because great part of the world population lives in the coasts and banks of rivers
and estuaries.
In the regions of abrupt topography, many hundreds of thousands persons live
in poor settlements located in unstable hillsides, especially vulnerable to intense
rainfalls. In the last decades hundreds of persons died or were seriously wounded
and thousands lost their homes due to the collapse of areas in Rio de Janeiro, Sao
Paulo and Santos (Commission of Health and Environment of the WHO 1992).
Slums that surround the big cities of the region are installed sometimes in the
drainage valleys of rivers or superficial currents, whose flood frequency has
increased as consequence of the climate trends (chapters 5 and 6). For example,
copious rains, from the beginning of January 2004 and for more than one month,
poured over regions of the Northeast, South, centre, West and Southeast of Brazil,
provoking land slides and floods and causing the death of 84 persons, whereas more
than 40000 lost their homes and other 63000 decided their self evacuation. In addition,
there were damages due to energy supply cuts, destruction of the infrastructure
of entire neighbourhoods, bridges and roads. The situation affected 338 municipalities
of 15 states of Brazil and the economic losses, only assessing the destroyed
housing, reached near 34 million dollars.
In Paraguay, the floods of the Paraguay River cause millionaire losses, affecting
thousands of persons, destroying houses, public buildings, roads, cattle and
farms. A preliminary estimate indicates that more than 60000 persons were damaged
in the 1982/83 floods. Another relatively precise record carried out by the
Committee of National Emergency (CEN) of Paraguay estimated in more than
70000 persons those who resulted affected by floods of the Paraguay River and its
tributaries in 1992. In the 1997 and 1998 floods, the affected people were near
25000 in Asuncion (principal urban centre of Paraguay) and more than 80000 in the
rest of the country.
In Argentina, the damages of the 1983 flood reached a total of approximately
965 millions of American dollars. These figures only amount the losses due to direct
damages suffered by the cattle rising, agriculture and infrastructure (Aisiks 1984).
A great part of the economic and social damages including lives losses produced
by the floods in the La Plata basin are due to the occupation of currently
floodable areas in the flood valleys of the rivers. This occupation was done before,
but in some cases after the pronounced climatic regional change that began in the
1970 decade (Chapter 5), which has increased the frequency of floods (Chapter 6).
Land planning policies are required to face this current situation as well as the eventual
threats of even greater floods in the future.
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