SAO PAULO (AlertNet) – Increasingly heavy summer rainfall, linked to changing climate conditions, is taking a worsening toll on Brazil. Just this month, 30 people died when heavy rain caused landslides in Petrópolis, a city located in the highlands of Rio de Janeiro state.
Such cases are becoming more common around the country. In São Paulo, Brazil’s largest city, at least two people died this summer due to urban flooding. And in January 2011, also in Rio de Janeiro state’s highlands, more than 1,000 people were killed by massive landslides and flooding.
The growing threat is driving officials in São Paulo and Rio, the two richest states in Brazil, to look for solutions to avoid worsening loss of life.
TURNING TO ‘BIG POOLS’
One measure adopted by the city of São Paulo is creating gigantic water reservoirs known as “big pools” (“piscinões”). This method – which is used in other countries like Japan and the United States – channels rain water that fall into the sewers directly to the reservoirs, and from there it is pumped slowly to the sewage system. This delays the water flowing directly into the rivers, reducing the risk of flooding.
Today São Paulo has 20 “piscinões” fully operating, able to contain up to a combined 5 million cubic meters of water, or enough to fill 2,000 Olympic-sized swimming pools.
São Paulo also adopted early this year, during the height of the rainy season, a series of measures to diminish the effects of heavy rain on the city. Among them is a 150 million reais (around $75 million) investment in improving drainage. Projects range from regular cleaning of gutters and sewage branch lines to the construction of five new “piscinões” over the next few years.
In other areas in São Paulo state, the government has purchased 186 electronic “pluviometers” which measure the amount of rain falling in more than 30 cities. Officials hope improved monitoring of rainfall will help prevent floods and other related disasters.
One of São Paulo’s biggest flood risks, however, is proving harder to address. Starting in the 1950s, some of the city’s largest avenues and highways were built on the top of creeks, which were covered and canalized. What was meant to be a transport solution, however, is increasingly becoming a huge problem.
“Sometimes, when it rains heavily, we can see water splashing like fountains on these roads, because of the overcharge in the underground drain galleries”, said Benedito Braga, president of the World Water Council and a professor of engineering at São Paulo University (USP).
“People back then didn’t realize that, with the creeks being covered and canalized, water goes from one creek to another, and to another, and so on. And little can be done now”.
Another problem is that São Paulo’s ability to absorb rainfall is very low, due to the large amount of concrete and asphalt covering the ground.
Braga notes that because São Paulo’s metropolitan area is formed by many cities that have grown together, each with its own government, no flood prevention strategy can be efficient without coordinated action by all cities. He believes the area’s mayors need to create an entity that coordinates anti-flooding measures.
CONCRETE WALLS AND WARNING SYSTEMS
In Rio de Janeiro’s highlands, where landslides are the worst danger, federal and state governments have invested more than 200 million reais (roughly $100 million) in soil containment works on the hillsides. Huge walls made out of concrete have been raised in an effort to avoid disasters like the one in January 2011.
Alert systems were also installed in the three cities hit most heavily by rainfall in 2011 – Teresópolis, Petrópolis and Nova Friburgo. Now residents can be warned of the risks of heavy rain either by text messages or by loudspeakers and sirens set on the streets.
But another disaster prevention program remains incomplete. In 2011, federal and state governments promised to build 5,000 new houses in safe areas, for use by people affected by heavy rain and landslides in the highlands. By January 2013, however, works had only started in the city of Nova Friburgo – the two other cities are still to see any work to be done at all.
Officials blame bureaucracy in financing and difficulties in finding proper areas to build the houses for the delay in the work. But because of the delays, many residents of risky areas have opted to come back to their precarious homes.
The World Water Council’s Braga says that, with the increase of rain due to climate change, no structural works – such as barriers or containment walls – can be sure of holding back the kind of worsening flooding and landslides that happen every year in Brazil.
“Places where flooding or landslide risk is verified, like river banks or hillsides, should remain uninhabited, end of story. It’s the mayors’ responsibility to impose their power and prevent these areas being occupied,” he said.
According to Braga, climate change now should be accounted for in each and every flood prevention project discussed in Brazil.
“Every year we see officials using heavy rain as an excuse, saying it rained more than predicted for the summer. But what is predictable? We have to build mechanisms that bring more resilience to the [flood prevention] system. We can’t do calculations based on data from the past, because we don’t know what the future is going to be,” he said.
Rafael Spuldar is a journalist based in Sao Paulo.