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| Holding ponds in Navi Mumbai (photo: NMMC) |
Navi Mumbai, a planned sister city of
Greater Mumbai was planned by conceived by Charles Correa, Pravina Mehta and
Shirish Patel, and planned and executed by CIDCO. Navi Mumbai has a unique
geography and topography. It is bound by Parsik hill, Sahyadri range on one
side and Thane creek on the other side. The relative ground level at Parsik
hill range is between 30 to 65 m RL and it drops down to sea level at Thane
creek.
The planners of Navi Mumbai have shown commendable
foresight and environmental sensitivity by preserving the original lay of the
land and working within the constraints of the natural topography, with minimum
damage to the natural environment. The land between the creek and the mountain
forms the developable land for the city. Navi Mumbai consists of 29 villages
(source: Navi Mumbai Municipal Corporation, NMMC). These villages are located
on higher ground on the hillocks. The lower levels were subject to high tides,
with salt pans and rice cultivation in these low-lying areas. This means, Navi
Mumbai is located below the high tide level.
In order to develop the land, CIDCO had to
raise the ground level. So, instead of flattening the mountains to raise the
ground level above the high tide line, the planners adopted a more innovative
solution from the Netherlands, a country that is located below the sea level.
The system is called the "Dutch Method". The system uses retaining
walls and flap gates to prevent the ingress of sea water during high tide and
allows the rainwater to flow into the sea during low tide, either naturally or
by mechanical pumping. Holding ponds are created between the low-lying land and
the sea that hold the rainwater and storm water runoff during high tide, and
siphon it off to the sea during low tide. This method requires less reclamation and hence less quarrying of the hills.
The Navi Mumbai storm water management
system consists of a series of drains and nallahs, holding ponds and bunds to
control flooding in an environmentally sensitive way. These holding ponds act
as retention basins during normal conditions and act as storage during high
tides. These holding ponds, and the hills have provided Navi Mumbai with a
large proportion of open spaces and natural areas, and opportunities for
recreational spaces for the public. According to NMMC, Navi Mumbai is perhaps
the only city in India where storm water and waste water disposal systems are
segregated.
In planning and designing our new urban
environments, whether new green-field cities or rejuvenation of existing
cities, we should be ever more sensitive smart about responding to the natural
environment. This attention to environmental sensitivity should not only be at
a superficial level, but should be built into the DNA of the city right at its
inception.
There is also a need to keep one eye on the
current global environmental trends and into the future. For climate change and
rising sea levels is a phenomenon that is threatening the existence of many
coastal cities. Even the Dutch are struggling to engineer new ways to battle
the rising North Sea, that threatens to take over its cities.
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