Dead end for the stormwater

Heavily encroached, the stormwater drains (SWDs) are undoubtedly in deep decay across the City.

 But equally to blame are the poor design, maintenance and management of these drains, so critical to preventing flooding of roads and low-lying areas. Adding to the chaos, SWDs and the underground sewage lines are under two different agencies, triggering serious issues of coordination and planning.

Last November, a record downpour of about 100mm in a day - arguably the heaviest in 44 years - had dramatically brought to the fore the severe shortcomings of Bangalore’s drainage system. But as BBMP and BWSSB prepare for another challenging monsoon season, the SWDs and sewerage lines largely remain what they were for years: Extremely vulnerable to mixing of rainwater and sewage, overflowing and flooding. 

The stench emanating the SWD near Cambridge Layout is a pointer to the pathetic state of these canals across the City. “I haven’t seen the authorities ever clean this drain. There is an apartment block close by from where sewage is directly let into the SWD. The nearby slum dwellers defecate into it. The stink is unbearable,” complains Srinivas N, a travel agent, residing in the vicinity. 

The impending monsoon is bound to worsen the scene. “The last time it rained, sewage mixed water had gushed into our office. There was a reverse flow from the canal,” recalls Srininvas’s colleague, Sathish Kumar. It is not going to be any better this year, since the roads, footpaths, roadside drains and shoulder drains are not aligned scientifically to quickly drain out the water. 

As civic expert A Ravindra points out, rainwater accumulates inside potholes and depressions on the roads severely slowing down the drainage process. Since the connectivity to the roadside drains to shoulder drains  and to the main SWDs is often flawed due to encroachments and clogging, rainwater floods roads, entering houses and underground sewer lines. The flooded underground pipelines force manholes to open, triggering a terrible concoction of rainwater and sewage.

Toilet atop drain

In Annasandrapalya, a toilet built right atop the SWD is a sign of the blatant disregard to rules and civic discipline. Plastic, garbage-filled polythene bags, construction debris and other filth are dumped into the already clogged canal. Neighbours say they are aware of the consequences. As Vinay Kumar, a medical transcriptionist explains, the clogged drain is an invitation for disaster this season too. Last year, he and his family had spent several days clearing out sewage-mixed water out of his house lying a few feet from the SWD.      

Then there is the bigger issue of large sewer pipes located within the drainage channels. This has severely impacted the efficiency of SWDs, as pointed out by Indian Institute of Science (IISc) researchers, T V Ramachandra and Pradeep P Mujumdar in their case study on “Urban Floods of Bangalore.” The presence of these sewer pipes, says the study, “has led to significant reduction in the stormwater system with obstruction from sewers and also from the sewer manholes.” This has caused “significant turbulence and redirection of the storm water flows, during high storm water flows, resulting in erosion of the bed and bank instability.”

Manholes within

The manholes and sewer pipes inside the SWDs also restrict drainage rehabilitation and maintenance works, including stabilisation, widening and desilting activities. Notes the study, “Manholes in drainage channels trap significant amounts of solid waste as well as localised sediment deposits due to the reduction in velocity of flows.”
 BBMP, with its limited resources, claims it does its best to desilt the drains. But what about the encroached space on either side of the drains that actually prevent any JCB to come anywhere close? There can be only one answer when the most violated of rules remains this: A minimum of 50 mtrs on either side of primary drain, 25 mtrs on both sides of secondary drains and 15 mtrs along tertiary drains should be treated as buffer zones!