On Tuesday morning, Gaurav Munjal, the chief executive officer of education-technology firm Unacademy tweeted a video of his family and pet dog leaving their Bengaluru residential complex in a tractor. “Family and my Pet Albus has been evacuated on a Tractor from our society that’s now submerged,” his message said. “Things are bad. Please take care.”

Munjal was among the thousands of Bengaluru residents who have been forced out of their homes by the intense rains that have flooded several parts of the city, leading to waterlogged residential complexes, power outages, massive traffic jams and disruptions in flights.

So far, one person has been reported to have died as a result of the downpour.

The city, regarded as India’s high-technology hub, received 99 mm of rain in the 24 hours until 8.30 am on Tuesday. The previous 24-hour period saw 131.6 mm of rainfall pour down on Bengaluru, its wettest day since 2014. The India Meteorological Department has predicted that heavy rain will continue until Friday.

But the intense rain is not the primary cause for the waterlogging – poor city planning is to blame, says Vishwanath S, an urban planner and civil engineer, who teaches a course on water as an adjunct professor in Azim Premji University.

Vishwanath, who has also worked on the Karnataka Water Policy in 2019 and is a technical advisor to the Bangalore Water Supply and Sewerage Board, explained why this spell of rains is causing unprecedented damage.

Excerpts from the interview:

Is heavy rainfall the only reason for the flooding?

No, that is not the only reason for urban flooding. It is bad infrastructural design.

For instance, roads themselves are not being defined properly and are acting as a barrier for water flow. The design of the storm water network, including the lakes and the drainage channels…the inability to connect the catchment areas to the drainage systems…All these issues have been incrementally getting worse over several years and now we are seeing the impact of ignoring all of it.

Concretising anything increases the water that runs off by factors of four and five. This means that if rainfall falls on soil, about 20%-25% will run off and come to the drain. However if you keep building, then the water that runs off will be 90%-95%. This water then needs a healthy system to be disposed of. Currently that system is severely underdeveloped.

Old Bangalore has barely been affected. Why is that?

Yes, the north, west and south are relatively not affected at all, or affected in a minor sense. It is the southeast [part of the city] which has been dominantly affected.

The parts of Bangalore that have not seen flooding, have seen an investment in storm water drains. So they are able to handle the floods for now.

But the southeast part is where the flooding is happening. This area is not only low-lying and is relatively flat, but has also seen an explosion in growth. In comparison to this reality, their investment in infrastructure has been very low. This area is on the outside of the Outer Ring Road and has been incorporated in Greater Bangalore.

Other than that the geographical terrain of Bangalore also plays a role.

Bangalore has the ridge line, the highest point to the land which separates two watersheds. On the west of which is the Kaveri Basin and on the east is the Dakshina Pinakini river. There is a steep slope so the water quickly runs off from the north to south.

The west of the city will be flooded if the storm water drains burst. But to the east of the ridge line, the flow of water is from west to east and it is slow and gradual. To add to this, the lay of the land in this area is very flat as it used to be paddy fields. In the absence of a field, the water does not run off slowly.

What this means is that the southeast part of Bangalore, which is already vulnerable due to how it is placed geographically, where the most robust system of infrastructure is needed, lacks government investment in robust infrastructure.

One of the biggest flood-affected layouts is the Rainbow Drive, which was an exemplar for water management. They had done rainwater harvesting, at the layout level. They had installed a sewerage treatment plant, they were doing solid waste segregation totally. They were dependent on one bore well for which they had done excellent rainwater harvesting, that was fulfilling all their needs. One of the best in the city, if not the country’s best projects.

Now the storm water drain from outside the layout has brought water and dumped it at their gates, without crossing over the road and taking it to the next lake.

This is the Sarjapura Road, which is R feet above the Rainbow Drive entrance.

So instead of going to a lake, the water from here goes to the rainbow drive entrance and their water levels increase. The Sarjapur road drainage should have been more adequate to take the rain water and ensure it went all the way to the next lake and not just dump it elsewhere.

As a result, motorboats are being used to bring people out.

Now they are building a culvert.

Have policies and guidelines been flouted over the years for this situation to have developed?

The master plan that is now in place, which determines storm water drains and how it should be developed, is a 2015 master plan. It was developed in 2007 and was called the 2015 master plan. It has not been upgraded. These master plans have to be developed every ten years.

The next one which is the 2031 master plan, has been at a draft stage and gone through several stages of debates, but has not been notified. It was published in November 2017 but everyone is unhappy with something or the other in the plan.

Some sections are unhappy about the nature of mixed-use development that has been suggested. Some are unhappy with the peripheral use of the Ring Road that has been suggested. Some are objecting to the environmental consequences of the master plan.

What needs to be stressed is that on the ground you are doing nothing. As a result, there is no stormwater management master plan for the people of Bangalore.

Are poorer localities been affected too?

There are a lot of informal areas around the Information Technology hub that have been affected. These areas are not being documented or being shown. They may or may not be legal slums, which is more concerning as that means there is a good chance they would not even have the inadequate drainage systems in place. Then there is the periphery of the state which is being affected, which is not being documented and shown either. The focus has been on the apartments worth Rs 9 crore or Rs 13 crore or the villas which have been flooded.

The area outside the city, called Mugalur, is not being adequately covered.

This is where all the water from the storm water drains come and join the Dakshina Pinakini river. The river has overflowed its banks, spreading across the banks. This has caused immense destruction to farm land. Those who grow flowers, vegetables and rice are deeply impacted. This stretch of the river goes for about 15 km till it reaches Tamil Nadu. So, all along the river the land along the banks have been affected.

For instance, there is a pig rearer I know there who woke up last night and saw water everywhere. First thing in the morning he saw his pig shed was getting submerged so he moved 300 pigs. Luckily, the village came together and helped him to get the cattle out.

There are farmers growing flowers and all of them are submerged. It is a complete crop loss. There are farmers growing fodder, it is a complete loss for them too.

More than a thousand pumping stations are submerged.

In terms of cost, the damage would be running into crores.

The State Disaster Relief Force and other teams are going into villas, but not to these river banks. People here are helping themselves.

This sounds like a full-blown crisis.

Yes, and it shall continue. It calls for documentation of who will be displaced when the encroachments happen. Will large office buildings and villas be removed? Less likely. Will the poor watchman be displaced? More likely.

Unless storm water drains are identified and marked with geo-tagging, it will always be the poor who will bear the bigger burden.

The climate crisis is already upon us. Temperatures have gone up by about 1 degree-2 degree Celsius, especially the minimum temperatures. The precipitation rate suggested when climate change strikes was a 6%-8% increase, that seems to be happening if we take the track record of the last three years. So now we have to prepare for a new normal, for rainfall of about 1000 mm-1200 mm annually, rainfall intensity of 180 mm per hour and continuous rainfall of three-four days. So that is the new normal we need to build infrastructure for.

Traditionally our infrastructure, including rooftop rainwater pipes and storm water drains, are designed for 60 mm per hour rainfall.

We need an audit to find where such a system is in place, and if is designed to prepare for such heavy rainfall.

In the absence of updated and relevant maps, or maps in the public domain, one cannot even scrutinise the extent of the concern.

What can we do in the short term and long term?

Short-term solutions would be an audit of the storm water drainage system, the lakes and removing every encroachment on these lands to protect the drains and lakes. The second is to ensure better links and connectivity between drainage systems. Identify them and fix them fast.

The long-term solutions would be to develop the 2031 master plan, including a storm water drainage plan and invest in that large-scale infrastructure factoring the changes due to climate change. Make the maps available to everybody.

However the government has gone into silence. They are not pushing themselves to develop better infrastructure.

Why is the CAG report from 2021 important?

The Comptroller and Auditor General is a constitutional authority. The audit was of the storm water drains and was awarded by the CAG for how nuanced it was.

Hopefully the government pays attention to it now. The report has gone in very thoroughly into the lacunas in the storm water management in the city. It is not a simple audit: it is what is called a performance audit. It looks at effectiveness, efficiency, what goes down institutionally, all that has been examined here.

What we are experiencing now, the flood devastation in Bangalore is the tyranny of small decisions. What happens is we take individual decisions when it is not raining, when it is a low year of rainfall, we do not understand the implications of our actions.

Suddenly, all the misdeeds cause a huge problem. We need a more robust oversight mechanism so that before any building is constructed we make sure it is legal.