Two years after the Chitale Committee, the fact-finding team studying the 26th July deluge of 2005, first recommended a contour mapping exercise for the city, the crucial topographical maps will finally be ready by the next monsoon. The Brihanmumbai Municipal Corporation’s planned ‘flood modelling’ system depends on the contour maps, which show topographical features of land in greta detail. A flood modelling system, in turn, will help the civic body predict and plan for major flood situations in the future.

After rejecting the demand for low-flying aerial photography — a necessary prerequisite for the contour maps — owing to security reasons, the Ministry of Defence has now given its approval to conduct the exercise. However, high risk areas like the naval base, Mumbai Port Trust, the Bhabha Atomic Research Centre and the international airport will not be included in the final maps.

The MOD approval, with certain conditions, came on September 17. Work will begin in the next few days. “The base maps will be ready by next year and so will the contour maps. We are trying to meet the target of monsoon 2009,” Additional Municipal Commissioner R A Rajeev.

Contour mapping is the most important element of a flood modelling system, as it shows points of elevation (height) of valleys and hills, and the steepness of slopes by using a curve connecting points. The mapping requires low-flying aerial photographs which will be taken from a height of 1,000 metres , with a high resolution of 1 is to 50. The distance between two points on each curve will be 20 cm, which means the maps will be adequately detailed so as to enable the plotting of minor storm water drains, river tributaries and even every manhole on the maps. The civic administration has selected private company MWH - Mumbai and ORG Informatics, Gurgaon, for the job.

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