Contoured Landscapes Prevent Flooding

Unsustainable storm water management is the main reason Chennai flooded. A city built over an inadequate groundwater system is as useless and ineffectual as a pair of trousers without the zipper or buttons

Published: 19th December 2015 04:29 AM  |   Last Updated: 19th December 2015 04:29 AM   |  A+A-

Landscapes

CHENNAI: It will be a while before the city stops talking about the floods. We are overflowing with thoughts, ideas and opinions on what caused them — bad urban planning, bad infrastructure, bad governance — the list of stuff that is not ‘good’ is endless. As an architect and urban planner myself, people often ask my opinion on why this happened even during casual conversations. What happened was simply unsustainable storm water management.

Stormwater management is one of the most basic things that every site/city needs to address. The sustainable indices rate them as part of some of the most fundamental check boxes while dealing with any development. Conveying water safely may not be the most creative thing an architect does, but is definitely necessary. Like it is important to ensure that the tailor puts a zip on the trousers — not hugely creative, but very essential.

The major complaint of many housing developments was that the water had nowhere to go. The surface water table itself rose and there was water gushing from the overflowing waterways onto the inundated streets. It was strange to see streets like mini-rivers and small pumps perched on compound walls pumping water out. The earth surface was soaked and there were no channels to convey the water out. Would it not have made sense instead to send this water back into the deep aquifers of the earth and save it for the future?

Pavitra.jpgAs far as best practises go however, we HAVE to plan for a minimum number of rainy days annually. However good design must also be sustainable for extreme conditions. The most creative way to do this on a city scale is to have clear, garbage free water ways — clean embankments and allowances for the water to rise during heavy rains. This will give us beautiful waterfronts, parks and recreation spaces yearned for in a large metropolis.

Swales are an elegantly efficient solution to counter floods and water stagnation! Swales are contoured landscapes lined with pebbles and plants. They have bore holes on the bed drilled up to sandy or rocky sedimentations underground; and are fitted with slotted pipes which convey surface water to aquifers below. 

The holding capacities of swales can be planned. They are surface water retention ponds and their excavated depths can be calculated based on the annual rainfall and maximum flood limits of any development site. Therefore they are designed to drain the site quite efficiently. It is a way of ensuring that even when there is too much water, we still convey it through the natural permeability to a depth where it can be collected for future use.

A swale, as per the concept described, has been operational for several years at a residence, and even managed to stand up to the recent Chennai deluge!

Don’t pump the water out of your homes, save it. Don’t dry up the ground water, recharge it!

 

(The writer is an architect, urban designer, dancer and chief designer at Shilpa Architects)

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