Unplanned urbanisation on Hulimavu lake floodplains worsened B'luru floods, says expert

On Sunday afternoon, around 300 people found knee-deep water inside their homes in Bengaluru’s Hulimavu and BTM Layout area. Though the reason for the unprecedented amount of water that entered people’s homes was reported to be a lake bund breach, the actual cause is a bit more severe and worrisome, experts say. For in the case of heavy rains, the people living around Bengaluru’s many lakes could face such inundation every time. 

The area that flooded on Sunday is the floodplain of the Hulimavu lake. A floodplain is defined as the area of flat land alongside a river. This area is the first to get covered in water when a river floods or overflows and usually if left empty, the water percolates into the ground itself or has the space to flow away. 

However, unplanned urbanisation in floodplains and the tendency of authorities not to follow plans have converted Bengaluru into a sort of a cement block that does not allow extra water to percolate or flow away. 

“In a rational environment, what we have to do is to delineate the floodplains and avoid construction on those flood plains,” says Raj Bhagat Palanichamy, a GIS expert based in Chennai. 

“In Bengaluru, unplanned urbanisation and not adhering to plans when the regulation in itself is minimal, has led to a rampant urbanisation process. These floodplains used to be agricultural land in Bengaluru. Now, we have built layouts and apartments on it. The effect of the Hulimavu lake breach could have been minimised if these flood plains had been conserved and left alone,” Palanichamy adds. This leads to excessive flooding even in the event of a small breach.

Satellite image animation shows d destruction of flood plains in Gottigere -#Hulimavu- Madiwala valley due to unplanned urbanization

Now there's no space to hold water during floods n no space for percolation either

Today when Hulimavu lake breached it's flooding neighbourhoods pic.twitter.com/6KyhDmPcsb

— Raj Bhagat Palanichamy (@rajbhagatt) November 24, 2019

According to the Karnataka government website, there are around 81 lakes in Bengaluru, out of which 34 are recognized as live lakes. While most were mainly formed for irrigation of the areas downstream, a couple of lakes in Bengaluru were formed to provide drinking water to the citizens living around the waterbody. Palanichamy says that the area around all the lakes in Bengaluru has now been urbanised. 

“We are not protecting our floodplains. What matters is not the distance between the lake and the construction, we have to keep in mind where the water might flow, where the floodplain is - in Hulimavu lake case it will flow to the north - and we have to keep in mind the elevation of the area,” Palanichamy says. 

So what can be done?

“For newly expanding areas, it is important to delineate the floodplains and not allow any kind of constructions. For the already existing urban settlements, we need to delineate the area and the floodplains and build resilience plan around it with an engineering angle. Currently, stormwater drains in the city are not enough because half the time sewage is dumped into them. We have to figure out a way to reduce the sewer water flow and reuse the sewage water,” Palanichamy says.

This may not just minimise the floods in case of a lake breach, but may also help during monsoons as well. 

Read: Hulimavu lake breach: Residents left to clean up as civic body indulges in blame game

Lost lakes, encroached drains: Why some parts of Bengaluru flooded worse than others