In late July, residents of southeast Bangalore – the city's IT hub – woke up to knee-high water in their homes. Torrential rains had flooded parts of the city, stirring officials of Bangalore’s municipal corporation into action.

Close to 600 houses were submerged after the city received its heaviest rainfall in five decades.

In response, the civic authorities revived their drive to demolish buildings that have come on up on the city’s storm-water drains, something that they have been undertaking piecemeal over the last three or four years. In all, the Bruhat Bengaluru Mahanara Palike has identified 1,923 encroachments, of which they have cleared close to 1,000, civic officials said. Of this, close to 150 structures have been razed this month alone.

But the drive, which has displaced hundreds of residents, has met with protests, legal challenges and allegations that the civic body is sparing big developers while going after smaller fish. There is panic spreading among residents who are now wondering whether their building will be next. Many residents have claimed that they were not aware that their homes were built over storm water drains, while others have said there are no such drains in their areas.

Why the frenzy?

Bengalore reportedly has 857 km of storm-water drains, of which 380 km have been encroached upon.

Curiously enough, the municipal corporation has been using village maps that are more than a century old to locate these rajakaluve – as storm water drains are locally called – and identify the structures that have been built over them, allegedly as encroachments.

Some of these maps were drawn in the 1890s, when a lot of what is part of Bangalore city today was village land. Over the years, there has been rampant real estate development in these sections and the landscape has changed to such an extent that it is difficult to locate a point on these village maps on the ground.

Somewhat paradoxically, the municipal authorities has to refer to century-old village maps to reform Bangalore’s sprawling urban landscape today because these maps seem to be the only legally valid land records for these areas.

Whose land is it anyway?

These village records were used by the British for revenue and tax collection in the pre-Independence era. "The only basis of demolition is the mother document, which are the village maps,” said urbanist V Ravichandar. "There are no proper urban documents where storm water drains are notified. The underlying village maps still define the city. Therefore Bruhat Bangalore Mahanagara Palike was forced to use village maps. Unfortunately, the citizens here are the victims."

During the ongoing demolition drive, however, many residents complained that they were not aware that their home had come up on land occupied by storm water drains – or that there is no rajakaluve there.

Most home owners also cite deeds and documents to show that they had purchased the house from developers and that this wasn’t an illegal encroachment.

Before staring construction on storm water drains, builders need the approval of the urban planning authority, the Bangalore Development Authority.

Experts, however, said that developers start construction even without this approval. By merely obtaining a sale deed called the khata, huge layouts and complexes have been constructed and sold to unsuspecting citizens. However, Bruhat Bangalore Mahanagara Palike issues a khata only for the building plan, not for the plot or area where the building is constructed. For this, they only take into account whether the developer has followed guidelines pertaining to parking and other matters.

“People are confusing khata with certificate of everything being kosher,” Ravichandar told Mint. "But the khata was merely a sale deed witnessing a transaction. The plot owners are taking the khata as a security blanket.”

M Shivaprasad, technical assistant to the chief engineer of Storm Water Drains Department of the municipal corporation said that since encroachments have not been marked in several of these old maps, the authorities will be conducting a fresh survey in a few areas using more recent maps sketched by the Land Records department in 2012-'13 to identify encroachments. This exercise will take at least a week.