It may not be cynical to say that “urbanisation” is a glorified synonym to uncontrolled growth covertly projected as an excuse of economic development and progress. Urbanisation is a damning reflection of our modern civilisation. It mirrors the dangerously degenerating civic sense of us citizens and the sickeningly hypocritical philosophy of governance of our leaders.

The prefix “urban” for drainage of storm water in towns, cities and metropolises, carries with it all the ills and frills associated with urbanisation. The term “urban drainage” is meant to represent a civic infrastructure aimed at safe management of storm water whose performance efficiency is an indicator of quality of life in and the developed status of a country

Unfortunately, in most of the Indian metropolises including “namma sundara Bengalooru”, this term brings dreadful images of flash floods, of overflowing sewers, of clogged open drains as solid waste disposal units, of women and children haplessly attempting to clear knee-deep polluted water in their tiny dwelling units, after even small-duration sharp showers.

Fault finding for this disastrous situation is an unrewarding and mad exercise. Because, each one of us as citizens, elected representatives, administrators, industrialists, scientists and technologists is at fault in one form or the other.  An important impact we ignore while planning urban infrastructure is that urbanisation creates (in space as well as in time) very high unmanageable densities of basic needs and generated wastes including urban storm output.

We have been paying a very heavy price for far too long by adopting quick-fix, ad-hoc, and unsustainable solution methods more to mitigate disasters (self-inflicted) than to prevent them. We should not lose any more time in changing once-and-for-all our mindset from unsustainable development practices to sustainable ones. This is the key to realise former president Prof Kalam’s vision of developed India by 2020.

Sustainable Urban Drainage Systems (SUDS) considers pre-urbanisation catchment response (storm output of rainfall) as their design target. The pre-urbanisation regime of natural terrain with more pervious surfaces, vegetative covers, depressions as detention and percolating ponds, etc, generates a predominantly slow and low flow catchment response which is easily manageable.

The simple design concept of SUDS is to treat each impervious land use unit (to the level of individual buildings, smallest of roads, etc) as an artificial Impervious Micro-Catchment, IMC (primary culprit of rain induced havoc)) and use technologies to source-manage the storm output of the IMCs such that we achieve slow and low flow outputs manageable by the existing drainage network.

What we need are systems for temporary storage of storm output of the IMCs and for controlled release of this storage either into permeable ground as a rainwater harvesting measure or to the existing drainage network at a manageable rate. Of course, a good solid waste management system is mandatory to effectively manage storm water pollution.

Many SUDS like filter drains, sub soil pervious shafts at intersection of drains, temporary detention ponds, etc have been attempted with varying degrees of success. The main challenges are efficient silt-trapping, water holding capacity of pervious mediums, and controlled release of stored water.

Of late very good SUDS have been developed, which are robust, cost effective and highly flexible to be customised to any site condition. One of them consists of plastic molded brick-like modular rectangular blocks with 95 per cent voids. Each block can hold 190 litres of water, when covered by a geo membrane.

The blocks have been so designed that they can be easily assembled to any shape and size to create temporary subsoil storage virtually anywhere; below the garage floor of a house, below an airfield pavement, by the side of roads, parking lots, etc.

If the hydro-geological conditions permit percolation in the subsoil medium, a pervious geo membrane around the blocks can be used to recharge the ground water reservoir. If the subsoil is impervious, an impervious geo membrane and an orifice controlled outflow regulating devise can be used to release storm water at slow and low flow target rates in to the existing drainage net work. This is definitely a sustainable drainage system.

Also, this system can assess each IMC’s storm water contribution to the main drainage network so that storm water utility taxing or creating any other meaningful policy or regulation is very easy. Probably, there is no better example of a sustainable development technology which uses biological non-degradability of plastic so beneficially.

Well, at least now should we not realise the importance of prioritising prevention over mitigation, of advance planning, of open mindedness to accept and adopt globally proven sustainable technologies, of sensitising citizens on quality-of-life-benefits by use of sustainable development technologies? Chak de India!