In a session at the 2011 GreenBuild in Toronto, architects and engineers discussed how cities can employ novel approaches to improve public health. Efforts to restore rivers, and also create earthquake and wind-proof buildings, can help communities become healthier, and also more resilient to population growth and catastrophic weather events.
The Value of Cleaning up Mexico City’s Rivers
Elias Cattan, Taller13 Arquitectura Regenerativa, proposed unearthing and restoring Mexico City’s network of rivers. Cattan said this project, while ambitious and somewhat costly, is crucial to “meshing our way of being with our ecosystems.” He pointed to other major cities like Los Angeles and Seoul that are planning or have already implemented major river restoration projects as models.
In Mannahatta: A Natural History of New York City, Eric Anderson shows how Manhattan looked before Europeans arrived. While it’s nearly impossible now to see the rich ecosystem that once existed on the island, in Mexico City, Cattan believes, it’s still apparent, just sullied. As a result, restoring that ecosystem “wouldn’t be a hard task.” Mexico City is a big sponge, with soil types that absorb water runoff from buildings. There are also some 45 rivers and more than 200 tributaries throughout the city.
With this megalopolis’ “catastrophic” population growth, there’s effectively been an “ecocide.” It didn’t need to be like this. Cattan asked what the ultimate purpose of Mexico City is in nature? “What is the vocation of Mexico City?” Relaying the ideas of Richard Lovelock, with his conception of Gaia and Earth as one large living organism, Cattan said “everything in nature has some purpose.” While the “process or purpose” of Mexico City may now be in a “state of constant oscillation,” the soils and river system of the city can still offer a range of valuable ecosystem services. For example, the rivers, once revitalized, could provide clean water again. He said “the rivers here, when they are born, are clean. They only become toxic as they make their way through the urban fabric.”
Mexico City’s rivers are 80 percent clean water, 20 percent human sewage. “Rivers here are lubricants for sewage flow.” While Cheongyecheon in Seoul and the L.A. River revitalization projects aim to accomplish a lot, Cattan’s plan would combine restored rivers with different “mobility systems.” Rivers would be lined with restored wetlands filled with “native flora and fauna,” and provide an “axis for public transport.” On either side of the river, there would be Bus Rapid Transit (BRT), which Cattan sees as central to alleviating Mexico City’s major traffic problems. Also, these wetland and river systems would function as parks – something that is vitally important in a city with only 3.7 square meters of green space per person (a level far lower than the U.N.-recommended 14-16 square meters per person). However, it’s not clear whether Cattan’s plan, which he estimates would cost some $350 million, also includes a low-cost waste management system that doesn’t take rely on the rivers.
Getting Serious About Earthquake and Wind Proof Buildings
If restoring rivers are crucial to human health in urban environments so is making sure buildings don’t kill during catastrophic weather events. Moving towards the realm of buildings, Ronald Mayes and Leonard Morse-Fortier, engineers with Simpson Gumpertz & Heger, argued that no matter what level of green certification a building achieves, it shouldn’t be considered green if it isn’t earthquake and wind-proof. Right now, most buildings, even green ones, are simply designed to protect people and don’t survive structurally, meaning all that material is wasted. Using “performance-based design” approaches, buildings can be designed to survive major earthquakes and storms.
Mayes said there’s a 60 percent chance an earthquake stronger than 6.7 will strike San Francisco in the next few years. A quake the strength of the one in 1906 would result in $111 billion in damages today. He wondered what the cost-benefit analysis is, what the threshhold is for paying extra for earthquake-proof structures. Right now, the extra cost “pay back is 3-7 years” on average.
A variety of new technologies, including “viscuous dampers, base isolation, rubber platforms” help make a 8.0 earthquake behave like a 5.5 one. Japan, with its high risk of major earthquakes, has taken these technologies seriously, building some 2,000 buildings using these approaches. In the U.S., there are just 200.
Mayes proposed a rating system or “report card” that could be posted on every building as a “communications tool for the general public.” He also called for “seismic resilience” to be adopted by LEED, perhaps as regional credits in earthquake-prone zones.
Morse-Fortier made an equally-sound case for wind-proof buildings. Right now, building codes “equal minimum standards.” In reality, trying to follow code is a “confusing process.” Still, he thinks buildings “shouldn’t fly apart in a hurricane,” meaning many developers and architects will need to go way beyond code to achieve true safety.
Making buildings wind-proof can be a costly undertaking. As a result, businesses and people need to do a cost-benefit analysis, and weigh the cost of creating a building that can survive high category hurricanes. Some buildings, like nuclear reactors and hospitals, “meet the criteria” for higher investment.
Wind can damage buildings through vibrations, “induced pressures and flows,” “windborne debris,” and “aero-elastic phenomena.” He thinks we should be able to “avoid cladding blow-out due to wind pressure.” Roofs gone missing are another avoidable problem. Furthermore, there are some types of roofs that are actually really dangerous. For example, he said “ballasted roofs” actually attack other roofs in a storm.
Morse-Fortier called on large-scale developments in windy areas to invest in wind tunnel studies. Even though these studies are an up-front cost, they help building owners figure out where they need strong structures and where they don’t. He said LEED should incentivize the use of wind-proof approaches and materials. It would have been interesting had he also discussed how green roofs perform in high-wind scenarios.
Image credit: ASLA 2011 Student Awards General Design Honor. Co-Modification Joseph Kubik, Student ASLA, Graduate, University of Pennsylvania
Faculty Advisor: Mark Thomann