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Flooding is not always that disaster you may have seen on TV: flooded cities, island people and animals, people who lose their homes with everything inside.
Floods are natural phenomena that happen in all rivers.
During the rainy season - which usually occurs during the summer in southern Brazil and during the winter in the northern region - rivers flood and flood the surrounding lands, called natural flood areas. This is good because water makes the land more fertile for planting. But man's action has changed the natural course of things…
In the old days, before cities were formed, water all entered the earth. When man began clearing vegetation and building houses on the banks of the rivers, flooding became a problem. Without tree roots, which act as sponges that hold water in the soil, the volume of water returning to the rivers increases greatly, and the risk of a "disastrous" flood increases together.
Things got worse in the cities, because the buildings, houses and the asphalt that covers the streets block the water's way to the land, the so-called "soil sealing".
Street rubbish also contributes to flooding because it clogs the culverts and causes streams to overflow.
When this happens, people are at greater risk of catching disease as the waters rise and carry this debris to streets and houses, along with rat urine (which causes a serious disease called leptospirosis). In these waters are also the unpipe sewers, which in many cities of Brazil are dumped in open streams without treatment.