Friday, May 4, 2018

The Mumbai DP - vertical development and population density are not the same!

The just approved Mumbai Development Plan 2034, while a mutilated version of the original ambitious proposal, does significantly increase the city's permissible Floor Space Index (FSI). It has also generated the usual debates about how deficient infrastructure would limit the gains from vertical growth. 

I have blogged about this on several occasions. This argument misses the point completely.

The issue is not at all about density. Among cities with population above 2.5 million, only Dhaka has a higher population density than Mumbai. 
The problem with Mumbai is not so much lack of density, but its very low per capita space availability - 4.5 sqm compared to 34 sqm in Shanghai! If we take the slums, the per capita space available is just 2.73 sqm, which makes those areas the densest urban habitation anywhere in the world at about 120,000 people per sqkm! Far from being the Maximum City, for its residents Mumbai is actually a Minimum City! The new DP aims to increase this to 18-20 sqm. 

In this scenario, vertical development is not going to increase the density significantly. In fact density could even fall. For, as height increases, the average size of each dwelling unit built upwards is likely to be much larger than the currently existing tiny single-storied and semi-permanent units that are a feature of the slums. To this extent, unless we go significantly upwards, the increased unit size is more likely to cause gentrification and, to thereby cause a decline in density. So, there is a logical likelihood that a small increase in FSI could actually tip over to a gentrification equilibrium which lowers density and makes housing less affordable for the less well-off. 

Infrastructure augmentation is important, but its deficiency is not as bad as is being made out, especially in the short to medium-term. In the long-run the likelihood of rising infrastructure investments may be more promising.

After all these same areas already have the world's second highest density. And they are less likely to have more people coming in. They have just about the carrying capacity - roads, mass transit, water and sewerage pipes, schools, hospitals etc - to support the existing population, though the quality of the provision is inferior, a concern not quite related to density itself.

Yes, we need  bigger water pipes and wider roads. But that, and the resultant increased service quality, depends on more city-wide water availability, more water and sewerage treatment facilities, more  and better mass transit options, better run schools and hospitals etc. This a felt-need irrespective of whether FSI remains the same or is increased. And the higher FSI does nothing to make it any more relevant.

4 comments:

Anonymous said...

"vertical development is not going to increase the density significantly. In fact density could even fall. For, as height increases, the average size of each dwelling unit built upwards is likely to be much larger than the currently existing tiny single-storied and semi-permanent units that are a feature of the slums. To this extent, unless we go significantly upwards, the increased unit size is more likely to cause gentrification and, to thereby cause a decline in density. So, there is a logical likelihood that a small increase in FSI could actually tip over to a gentrification equilibrium which lowers density and makes housing less affordable for the less well-off. "

The logic here makes my brain hurt, it's so innacurate imo. I don't know where to begin.

Ray Lopez said...

Manila is the most dense city in the world, not in the graphic, also very vertical (skyscrapers) and the roads are terrible, meaning you are limited unless you want to commute for several hours to the walking distance from your residence.

Gulzar Natarajan said...

Anon, thanks for the comment. I understand why the LOGIC of this makes your brain hurt. It used to hurt mine too before I DID this! My practical experience of doing exactly this in two big cities for six years - re-development of very dense but one-floor slums through vertical redevelopment - convinces me that, unless you go really up (a near impossible thing to do with poor people estates in a place like Mumbai, unlike the massive Chicago public housing schemes), you cannot squeeze out more people in that same land footprint. The percapita space availability now is that small.

Even in non-slums, given the density today, maybe you can squeeze a bit more people per land footprint, but not by much.

We are not at all talking about the really poshest areas (which are small proportion) and where renewal mediated by zoning policy as a tool may not have that much impact.

Just to get a sense pls see the map in

https://geographyeducation.org/articles/comparing-urban-footprints/

There is only so many people that you can squeeze into that tiny land!

Gulzar Natarajan said...

Thanks Ray for pointing that out. Yes Manila is missing in the graph.