Five years after flood, contour maps of city ready……sharvaripatwa
Over five years after it was first proposed, the Brihanmumbai Municipal Corporation (BMC) is finally ready with contour maps of the financial capital, key to building flood modelling systems that can aid monsoon management.
The contour mapping was completed recently and will now be used by the BMC for its various projects, said Addtional Municipal Commissioner Aseem Gupta. All data regarding the ground level and height of structures across Mumbai are now available under contour mapping. The data is based on the survey we conducted in July 2009, but the maps will be updated as new structures come up, said Gupta.
Contour mapping will not only be helpful to develop flood models, but also other purposes such as developing and studying road networks, said S K Railkar, Chief Engineer (Storm Water Drains). According to the official, the contour mapping will also help detect any new catchment areas.
Contour maps were first recommended by the Chitale Committee set up following the July 2005 deluge. Contour maps help build a GIS-based flood-modelling system that will include digitised maps showing the precise carrying capacity of drains, geological factors like hill slopes and riverbeds. It will have columns for areas, rainfall, drains and flood points and will predict which areas may flood at various rainfall levels.
The aerial photographs for the BMCs contour maps were taken from a height of 1,000 metres, at a resolution of 1:20. They capture all objects of 20 cm length and more. These maps are adequately detailed to enable the plotting of minor storm water drains, river tributaries and even manholes.
The BRIMSTOWAD consultants will also be using the contour mapping to study if there are any changes in their plans, said another SWD official.
The contour maps will help us identify the high and low areas in catchments. There will be individual maps for each of them to predict floods. Although none of the data and records can be made available to the general public, it can be use for all kinds of projects of BMC, according to Gupta.