Staying dry: Vertical or horizontal strategy for Sri Lanka?

August 02, 2007 (LBO) – Large parts of Colombo, particularly the roads, go under water whenever there is heavy rain. One explanation is that polythene bags are blocking the drains. In cities where polythene bags have been banned, there should be less flooding, if this is true.

Recently, I experienced heavy rainfall in Dhaka, Bangladesh, a city that banned polythene bags five years ago (Read Link) and is frequently cited as a model by ban devotees.

Five years after the ban, the floods are as intense as ever. Government bureaucrats going from one building to another inside the massive Bangladesh-Secretariat complex were wading knee-deep in water. In Sri Lankan terms, this was like the Secretariat next to the old Parliament going under water, not Orugodawatte or some low-lying area on the edges of the city.

The polythene ban has had negligible effect on flooding.

Differences and similarities

Both cities get spikes of intense rainfall, Colombo two (April-May and October-November), to Dhaka’s one (June-August). Colombo is wetter on the whole, but at the peak the two cities get about the same rainfall on average (close to 400 mm.). The design parameters for storm drains should be pretty similar.

Both are subject to increasing levels of flooding, affecting hitherto “safe” areas. If the cause is not seen as polythene, it is seen as over-building. But these cities are the engines that drive their national economies. For the countries to grow, these cities too must grow.

The question is, in which direction? In Colombo as well as in Dhaka, the city planners and the opinion leaders have not faced up to the hard truth. Cities must grow or they die. But for sustainable growth, they must grow vertically so that the population densities that are characteristic of major cities are maintained and enough green space is left to soothe the soul and to absorb the excess rainfall.

In both countries, the required cultural change has not yet occurred. Rocketing land prices are driving the building of apartments in both cities, but the cultures are hostile. “Apartments are ugly; apartments cause traffic jams; why can’t we go back to the good old days when there was room in every garden for a game of cricket?”

People still see apartment living as an inferior option. Even while horizontal growth is destroying the flood plains and covering up the soil and greenery in cement and they are ankle-deep in dirty water that has nowhere to go, they keep criticizing the high-rises.

It’s not the high-rises that are causing the floods; it archaic thinking about single-family dwellings.

The garden city

Singapore, once a seriously flood-affected city with average rainfall just a little below that of Colombo, has tackled the problem successfully. In the 196os and 1970s it built hundreds of high-rise apartment blocks.

It has the population density of a big city, but it has more green space than any city in Asia (perhaps the whole world). It has taken over the title of “garden city” from Colombo; and it is not periodically crippled by water-logged roadways.

Dhaka banned polythene is 2002; Sri Lanka in 2007. Singapore has not. It is only educating people on the need to reduce use (Read Link).

We can get serious about zoning. We can make sure that the horizontal growth is discouraged in the city core, except for heritage areas, and also in the main suburbs. We can also make sure that the sewers and other necessary infrastructures are upgraded.

Apartment living must be made the norm and single-family dwellings the exception. Land that is currently occupied by ugly horizontal sprawl must be converted to green space, to calm the soul and absorb the rainwater.

Without this fundamental transformation, Colombo will be in a race with Dhaka to see who gets waterlogged sooner. Banning polythene won’t postpone the day we will have to go to work in boats and rafts over putrid waterways; zoning, good sewers and high-rises will.