Block 2: Urban Systems: Access, Density, Green-Blue, Heat, Flood

What today is about

A neighborhood has to deliver several things at once, and they pull against each other.

Last class you asked whether you can live somewhere on foot. Today you name what a neighborhood has to deliver for that to be possible. Five systems do most of the work: access to daily needs, density (how many people live and work in a given space), green-blue space (parks, street trees, and water: canals, eris, wetland buffer), heat comfort (shade and airflow against the urban heat island), and flood resilience (permeable land and drainage that give the monsoon somewhere to go). These are the city-scale version of ecosystem services: the things a place provides for the people and ecology that depend on it.

The reason this matters for design is that the systems are coupled, so improving one often costs another. Pave more ground for density and you remove the permeable land that buffers floods. Add green-blue space to cool the heat and you compete with housing for the same limited ground. Widen roads for cars and you lose both shade and the short walking distances that made the place livable on foot. This is why a neighborhood cannot simply be made "better." It can only be tuned, with every gain paid for somewhere. The seven objectives you will quantify in the assessment sit directly on top of these five systems.

Chennai makes the coupling vivid. The city built over many of its eris (the old rain-fed tanks that once held the monsoon), and in 2015 the water had nowhere to go and the floods were catastrophic. Wetlands like Pallikaranai shrank as the city grew. The same paving that added buildable land removed the system that protected those buildings. Understanding that link is the K/U groundwork for every allocation you will make later.