Doppler radar may put cap on building heights

This means cities will have to curb, at least in some areas, the vertical approach to development they have encouraged as a way to tackle shortage of space. Local development bodies will not be able to relax their current restrictions on the height of the buildings at a later date as they may be forced to otherwise in an effort to create more space in cities.

It could also mean higher real estate prices in these neighbourhoods, which will now have less developed space than they could have had.

DWRs are an improvement over existing radars and can provide adequate warning of storms, hurricanes and freak weather phenomena, including tsunamis.

In a notification issued on 6 December, the Indian Meteorological Department (IMD) has said the height of the building will be determined by a formula where the distance between the building and the radar is the main variable. The further away from the radar the building is, the taller it can be.

For instance, in Chennai, where the first radars have been installed along the coast as part of the tsunami early warning detection system, IMD has fixed the maximum height for a building at 52.58m, with a tolerance of 5%, within a radius of 1km from the radar’s location.

A building that is within a radius of 10km can have a maximum height of 58.89m, with a tolerance of 5%—this translates into an area of 314 sq. km where buildings cannot be taller than this. This will affect a large part of the city. New Delhi, for instance, has an area of 1,483 sq. km. Mumbai has an area of 437 sq. km. The formula used to calculate the permissible height of the buildings is not city-specific.

Twelve DWRs are scheduled to be put up by next March and locations include New Delhi, Mumbai and Nagpur, but the precise locations within these cities have not been determined yet.

According to Prakash Kumar, joint secretary in the ministry of earth sciences, 55 radars are proposed to be set up in the next five years.

“Requirements for radar construction have already been communicated to the local town planning bodies," a senior IMD official said, requesting anonymity “Though the cap in building heights is not drastic, we are in sense preparing for the rapid urbanization in the country, and these caps will be strictly enforced," the official added.

Importantly, existing buildings will not be affected because the radar’s antenna can be designed to tower over tall buildings; it’s only the future trend of building heights that’s worrying IMD.

“...Due to rapid urbanization of cities in India, cities are becoming mega cities and towns are becoming cities. As a consequence, in most of the metros...a vertical increase in high-rise building is the normal trend," the IMD notification said.

The average height of Chennai’s high-rise buildings is between 40m and 45m, according to Subha Reddy, managing director, Ceebros Property Development, a Chennai-based real estate developer. “Even now we require clearances if we set up tall buildings near transmission towers (television and cellphone), so this would be another addition. We are not really concerned about this yet," he said.

DWRs are an enhancement over the current crop of radars, in that they can effectively calculate wind speeds of a developing storm or a hurricane, but require an unobstructed line of sight between the radar beam and the atmosphere. Current radars come with their own set of demands, but DWRs “are far stricter in their requirement", said the IMD official.

“I haven’t seen any communication about the reduction in permissible heights," said A.M. Athale, deputy chief architect with the New Delhi Municipal Council. “Permissible height depends on zoning. Commercial properties have height restrictions of 50m, while near embassies it is around 15m. Also, by-laws have to be changed for changing the height restrictions. The ministry of urban development has to change it. The Delhi Development Authority (DDA), as the custodian of the master plan, has to be involved," Athale added.

A DDA spokesperson said she wasn’t aware of any such request from IMD.

The DWRs, which have been imported from Germany, cost about Rs20 crore a piece, and that doesn’t include the installation and maintenance costs, the IMD official said.

Currently, five DWRs have been installed at Chennai, Kolkata, Machilipatnam and Visakhapatnam primarily to watch the Bay of Bengal, a hotbed of cyclonic activity.

“Doppler weather radars are extremely useful in dynamical weather forecasting systems, and their inputs greatly enhance the accuracy of preparing monsoon forecasts," said Madhavan Rajeevan, director, National Climate Centre, Pune.

Extreme events, including heavy concentrated downpours (such as the one that struck Mumbai in July 2005), have shown a marked rise in the last decade, said a report on climate change in India, prepared this year by IMD. The Dopplers promise to be “extremely useful for forecasting extreme events", the IMD official said.