Because of several reasons and amongst them the major one is availability of “Water”
The entire approach of urbanisation has been on reclamation of land which otherwise were natural water bodies just a century ago. Those water bodies now have a human settlement, which apart from a lost opportunity for recharging groundwater is also leading to urban flooding. Flooding means that there is rainfall beyond the natural capacity of the reservoirs of the area, and usually this water goes down in the drain and then to rivers flowing towards the oceans.
A national government may have an environment ministry to have an eye on the future, however a council may have a health division to take care of the day to day issues and the laters major budgeting also goes towards it. So a unified approach is very rare to arrive at thus resources such as rainwater aren’t being harvested to effectively feed the increasingly urbanised city. This non functional system over the last two centuries has become so imbibed in all our culture, that it has almost become an acceptable sin to live with.
Above: A Pool of water just floods a ground without any ways and means of being utilised by the city council.
Since while there is no unified approach at a city level in managing these resources, its but natural for the individual building owners and the gated communities not to think about it at all and Architecture at best is confined to beautification of a building rather than sustainability cause no one from the city council which governs the by laws is demanding it.
Usually, the total surface far exceeds that of the building’s area in any city. So merely imposing solar collectors or rainwater harvesting in a few isolated pockets may be just lip service rather than making the city actually sustainable.
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