The transformation of K-100 into Bengaluru’s “model” stormwater drain from “open sewer” to “success story”

Bengaluru: Residents of some areas of the city found it much simpler to wring themselves dry thanks to a “model” stormwater drain when torrential rains turned portions of the city into a sort of dystopian Venice earlier this month, with wet people travelling the streets on boats.

The Koramangala valley stormwater drain, or K-100, originates close to the Majestic area and empties into Bellandur Lake (which flooded during the downpour). It stands out in a city noted for its silt-filled drainage infrastructure.

The 12 kilometre drain, which has not yet entirely recovered, performed better than most of its clogged counterparts on the intervening night of September 4 and 5, when the city was flooded by 131.6 mm of rain.

When ThePrint arrived on Tuesday, the first phase of the project, which is the area around the drain near Shanti Nagar bus station, appeared picturesque. There was a large arena, lovely flora, and inscriptions that said “Citizens Waterway” on the walls. Two men were spotted strolling along a walkway and over a small bridge before climbing the stairs to the other side.

Just two or so years ago, the drain was little more than a garbage-clogged sewer, but it received a new lease on life when the Karnataka government decided to upgrade it under the supervision of the Bruhat Bengaluru Mahanagara Palike (BBMP), the city’s civic body, after Seoul renewed the 10.9 km concrete-covered Cheonggyecheon stream.

The outcomes go beyond aesthetics.

According to city architect Naresh Narasimhan from the Mod Foundation, who conceptualised this BBMP project, “the whole drain held up very well throughout last week’s monsoon save maybe for one location where the bund was inadequate.”

KR Market, Shanti Nagar, Hosur Road, Ejipura, National Games Village, Koramangala, ST Bed layout, and Bellandur are all stops along the K-100 drain before it ends at Bellandur. A tenth of the city’s sewage/runoff is carried by its 32 sq km watershed.

Even when passing through the historic city, the water flowed smoothly. Now that every bridge is connected by a single span, the river is clear and free of silt and solid trash. Since there are more tippers available along the stretch, people are also becoming more responsible and refraining from dropping plastic down the drain, according to Narasimhan.

The K-100 project is being promoted today as a prototype that may be expanded to assist Bengaluru be protected from floods. The project provides suggestions on how to adapt it to diverse conditions in a city with a growing population because it flows through several layers of land use under a variety of settings.

The project’s beginning
The National Green Tribunal invalidated the designs and environmental approval for a Rs 2,300 crore project on the Bellandur Lake wetland in 2016, in a precedent-setting decision. In addition to requesting a halt to building, the green court requested the reclamation of 3.10 acres of lake area and the restoration of several rajakaluves, or stormwater drains.

The city authorities started considering measures to revitalise the stretch after the NGT ordered the de-concretisation of the full length of the sewer.

With the assistance of urban planners and architects from the Mod Foundation in Bengaluru, the BBMP undertook the project to revitalise K-100.

B.S. Prahalad, the head of engineering for the BBMP, claims that so far, the project has cost between Rs 150 and Rs 160 crore and is intended to “bring back 32 acres of public space worth Rs 1200 crore.”

But there were challenges with the project as well.

The stormwater drain resembled an open sewer before the team started working on revitalising it. Garbage was dumped indiscriminately in large quantities, homes next to the drain dumped their waste there, industrial effluents mixed with sewage, and rainwater.

“The biggest challenge which we faced in K-100 was reworking the pipe drainage system from open flow to piped flow. We were able to divert sewage away from the drains and 900 trucks of silt were removed,” Prahalad said.

He claimed that eventually the team was able to return the gradient to what it had been before 2 metres of silt had been deposited by human waste running into stormwater drains. The drainage system was able to operate efficiently when the additional silt was removed.

“Before this, areas along the drain, including Koramangala, were getting flooded every year,” he said.

‘Water heritage’ restoration in Bengaluru with public assistance
Bengaluru is rapidly becoming more urbanised, and as a result, the original rajakaluves, or traditional irrigation canals, like K-100, have been congested with bottlenecks.

Prahalad thinks that repeating the K-100 method in these canals could produce excellent results, but it will also require support from the populace.

“K-100 is unquestionably a model. But first, the general public needs to speak up and demand that our rajakaluves be free of sewage. If sewage is evacuated from stormwater drains, desilting can be done, and an artificial river can be created. We can restore the splendour of the river system in this city if groundwater enrichment takes place, he said, and it would also help to reduce floods.

The goal of the project, according to Nidhi Bhatnagar, an urban designer with the Mod Foundation, was to introduce the city and its residents to their “water heritage,” yet many aren’t even aware that it exists.

“If you don’t know there is a water body flowing in a specific place since it is fenced off, how do you even let people know that this is something that is theirs?” she asked.

The group studied examples from China, Korea, and the Philippines for ideas.

One issue that jumped out was the importance of public participation in river revitalization initiatives.

“What was interesting about the [renewal of the] Pasig River in Manila was that it was quite charged with public participation,” said Narasimhan.

Several city and state authorities partnered on the K-100 project to raise awareness among residents on either side of the drain.

Communities now contribute plants to the wall-lined planters and take use of the open areas. The crew has observed a notable decrease in the amount of waste and sewage entering the stormwater drain over the course of the project’s existence.

“Unless you take out the sewage, the solid waste, and the silt out of existing drains, no scheme will work. All you have to do is this, and 80 per cent of the problem will be resolved,” said Narasimhan. “Encroachment is one part of it. The real bigger problem is silt, solid waste and sewage and the need to keep widening the width of the channel as you go along.”

The utilisation of artificial wetlands to clean and filter the water as well as the relevance of natural water systems for drain remediation were both highlighted by Narasimhan’s analysis of precedents from other nations.

“This is an important thing we need to bring to India, it is called constructed wetlands,” said Narasimhan. “We often assume that the only way to treat wastewater or liquid waste is through expensive membrane-based water treatment plants which need electricity and dosing of chemicals.”

“The guiding principle of this project was that we have to move from a grey to a green infrastructure paradigm. We must bring the public into public infrastructure,” the architect further said.

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