Amid threat of another deluge, some remedies for Bengaluru’s civic body

There was a lot of outrage after a female techie died while crossing a flooded underpass in a car in Bengaluru on May 22, 2023. The problems brought on by a deluge, triggered by sudden downpours accompanied by gusty winds, have been well known in Bengaluru for a decade.

Bengaluru city has problems with its roads, underground sanitary systems, water supply, electrical/other cables and storm water drains and traffic in the Central Business District area.

The city is expanding rapidly as surrounding villages, consisting of traditional narrow streets, merge into it. With the start of vertical growth in the city since 2000, civic amenities flooded the city, resulting in a huge amount of garbage, sewage and rainwater runoff.

The existing old roads of the city were developed to accommodate the civic demand for traffic. The tree planting along streets, roads, parks and around institutional areas — initiated to green the city for aesthetic and climatic values in the 1980s — started generating huge quantities of bio-wastes like fallen leaves, flowers on the streets, thereby doubling the task of cleaning the garbage.

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The city’s numerous lakes, connected with natural streams existing in the city, were occupied, encroached, polluted and choked, obstructing the disposal of runoff.

In the course of the city’s growth, underpasses were introduced to ease traffic jams on roads at circles two decades ago. Most of them are unscientific, with outlets for draining runoff at the lowest level of the underpasses, which gets choked with floating debris carried by the runoff from the roads.

Bengaluru city is a concrete jungle. The moment a downpour starts, there will be runoff, except in some open grounds and parks that allow percolation of some rainwater into the earth. Rainwater harvesting structures (RWHS) in houses and institutions, which collect rooftop rainwater, are other exceptions.

But the rest of the rainwater runs onto roads and into storm water drains (SWDs), with plastic, dry vegetative waste and dust choking the SWDs wherever obstruction happens. This choking of runoff is more common in the underpasses and in the curves, or at bottlenecks of the big SWDs.

There are remedies to address the problem of deluge in the city and can be considered by the Bruhat Bengaluru Mahanagara Palike (BBMP). There are as follows:

* Flash floods brought on by rains have to be checked with the creation of RWHS for all parks and playgrounds as well as to the runoff from the roads. This will help to contain the flood of water by storing and slowly disposing of it through soil filtration, which would also recharge the underground water table. There should be an arrangement to de-silt them once every two years.

*New houses should mandatorily have RWHS and old houses should be compelled to have WRHS. Many houses in the 1980s and earlier had ring wells for water, but they were closed by filling earth after the Cauvery water supply came to the city. Such wells have to be reopened to serve as RWHS. Defunct bore wells can also serve as RWHS.

*The remedy for debris choking the SWDs lies in the BBMP strictly implementing the ban on single use plastic manufacturing and arresting the use and throw culture practiced in the city with heavy fines.

*To tackle the problem of dry leaves/flowers falling from trees during a deluge, the forestry wing of the BBMP has to introduce the system of ‘tree training’ for urban trees. Urban trees have to be trained to grow straight without branching for a minimum height of 3 m, so that trees will develop the crown above 3 m and will not obstruct the traffic or vision of motorists on the roads. There should be a health survey of the trees after 30 years of planting to remove trees/branches that pose a threat to traffic, buildings and life, and replant the site of such harvested trees with 3-metre-tall saplings.

*The death traps in a deluge — underpasses of the city — have to be redesigned to ensure no runoff from the roads enter them, with catch water runoff drains at the start of the inward slope on either side of it. The rain water outlet at the lowest level of underpass should be reserved to drain out the runoff of its surface area.

* The desilting and maintenance of the big SWDs (rajakaluves)/old streams and small rivers in the city should be an annual job during summer to ensure that all the silt load deposited is cleared. Silt deposits surface wherever the velocity of the water flow goes down during floods in the SWDs, which require to be cleaned every year as a routine.

*Lakes in Bengaluru city, which numbered 127 as per Laxman Raw’s report in 1986, have come down to 100. Lakes are the source of flood control and aquifers of underground water table; habitats of aquatic flora and fauna; and recreation centres for citizens. But they are shrinking in area due to the dumping of desilted silt from the lake on the fringes and formation of parks. How long can we afford to shrink lakes’ area? We have to think of disposing the silt load of the lakes into farm lands or in some dumps. Lakes should be free from sewage and garbage that enter them during rains as well as from water hyacinth weeds.
(The writer is former Indian Forest Service officer and a writer based in Bengaluru)