studio toró is an architectural research practice devoted to building under 40 inches or more of rainfall every year
urban waters manifesto
In Latin America we have the equivalent of one Katrina every year. The number of deaths from urban flooding in the rainy area that go from south Mexico to northern Argentina hits the thousands, every year. In most of that region where 500 million people live, the majority of them in cities, annual rainfall is over 50 inches.
Nevertheless, large cities such as Rio de Janeiro, Sao Paulo and Buenos Aires have been struggling to keep their water supplies in pace with growing demand and drying watersheds. Meanwhile global warming has been fueling two trends: stronger storms and longer periods of draught, making water deadly both ways, when it falls and when it does not.
While the usual approach to the problem has been at the scale of urbanism and public policy, architecture has indeed an important contribution. We intend to look at urban flooding to argue that beyond matters of governance and infra-structure, individual buildings should do much more to engage water in a responsible way.
For 500 years we have been struggling with the rainy season in Latin America. For most of the region the amount of annual rain varies from 40 to 70 inches. In the majority of the region the rainy season is concentrated in the summer during which rainfall usually achieves 20 inches per month and it is not uncommon to have 4 inches in a single day.If 18,000 liters (5,000 gallons) can fall on a single regular lot (12 X 30 M) during a summer storm, you can imagine the impact of that much volume in the storm-water system of any major city.
In a historical perspective, it becomes clear that the Iberians who conquered the land around 1500s were never prepared for that much water, coming from places where it rains much less (21 inches in Lisbon, 11 inches in Madrid).
After independence the trend continued for the models from Paris (25 inches) or London (29 inches) have only about half the average rainfall of Brazilian cities, yet distributed evenly.
One need only to look at average building in most of the tropics nowadays and the inability to deal with rain becomes remarkable. Water infiltration is the rule in low-income houses which, in addition to being pressured by densification, have been paving every open space, resulting in a fully impermeable terrain. Yet the problem is not bound by income and class stratification, upscale apartment buildings are no less incompetent when it comes to water proofing and soil permeability.
If we can agree that any problem have the seeds of its solution, we can hope that a responsible architecture attitude towards water conservancy and soil permeability can have a tremendous impact in the deadly and costly path of water. Our main purpose at Studio Toró is to engage with the way architects design it and the public at large build to argue that both need to be much more serious about water.
A regular lot in a region under 60 inches of rainfall receives something in the magnitude of half a million liters of rainfall per year. Given the average consumption of 150 liters per persons per day in Latin America, the amount of rainfall in a single lot is double the consumption average of a family of four. In cities where water treatment is already available, rainfall could be used only to non-human uses such as flushing the toilets, watering plants and washing cars or pavements.
In the same regular home of 1000 sqf, only the water collected in the roof (160.000 liters) would be enough for non-human uses year round. A simple underground reservoir of 2 x 3 x 3 meters (18.000 liters) should be enough for storing enough water to undergo 3 month of no rain and still keep your home clean and your plants green. With the current cost in Sao Paulo of about R$ 5,70 (U$ 2.80) per m3, the economy is at the scale of R$ 912 per year. Simple treatment solutions can cost as little as R$ 0.16 per m3 or R$ 25 for the entire volume considered here.
The cost of the underground reservoir would be recovered in 3-4 years only.In terms of reducing the runoff even further, a single garden with 36 sqm (6 x 6 m or any combination of smaller gardens adding up to 36 sqm) receding 10 cm into the ground would be able to collect the entire volume of 10mm of rain falling into the property and allow it to infiltrate in about 1 hour maximum. Given that most soils in Brazil have an infiltration rate between 10 to 25 mm per hour, a simple system of gardens receding slightly can help all the water be absorbed into the soil
However, during the rainy season we need more than a garden to achieve zero runoff because the soil can become saturated after a few days of continuous rain. In this case the use of pervious pavement for garages and walkways can be very helpful. There is an enormous variety of ways of doing pervious pavement, something that all housing units should be using in the rainy areas of the world.
In addition, the use of runoff infiltration reservoirs can bring the level of recharge (and consequent reduction in runoff) to levels much closer to the natural landscape before urbanization. Studies by Araujo (1999) and Costa & Barbasa (2006) have demonstrated that pre-urbanization levels of infiltration can be achieved in most lots of 360m2 with a 1.3m3 reservoir or 76m2 of pervious pavement. In either case, the estimated cost of R$ 1,000.00 (about U$ 500) in the case of existing buildings, much less in the case of future construction which can incorporate those variables in its design and/or renovation projects.
The many different urban arrangements of the present time have advantages and disadvantages in terms of dealing with water. The North American traditional suburb, for example, present a high degree of permeability and has in the large lawn its most valuable asset, but it is unsustainable from the point of view of transit and extremely harmful to the natural environment for occupying vast amount of space with very low densities. Areas such as the Plano Piloto in Brasília seems to provide the best of both worlds: reasonable density, public transportation and high permeability. But the cost (those who live in Brasília know better) it is prohibitive for a large portion of the population
north-american suburb , density = 5hab/ha, permeability = 70%
On the other hand, the traditional city suffers from the opposite problem: high densities are necessary to cover the cost of the infrastructure and the concentration of services, making possible good transit solutions and consequently lower energy consumption. However, the use of space is so intense that almost nothing is free for water infiltration, causing heat islands due to absence of evaporation and flooding whenever it rains.
It is precisely in the traditional city that individual responsibility can make the difference. Let’s see the numbers:
In a normal block of 1ha (10.000m2) 100 thousand liters of water fall every time it rains 10mm (almost daily during the summer). If the block entirely covered, that volume of water goes immediately down slope via storm-water system or over the streets. Since each building can achieve zero discharge with a garden of 18x18ft or 800sqft of permeable pavement, the rate of infiltration can gradually return to pre-urbanization levels if each lot take responsibility for the corresponding volume.
Brasilia super quadra , density = 40hab/ha, permeability = 50%