It was hardly a month ago that Bengaluru‘s roads saw boats and fishing nets, thanks to the flood waters that engulfed the city. Finding the reasons for urban flooding is what a researcher from the city attempted to do, using geospatial methods.
In a study titled “Application of Geo-spatial Analysis of Causative Factors for Urban Flood in Bengaluru City”, Meena Y R, assistant professor at the Jain University, has attempted to find the reasons for flooding in various regions in Bengaluru which fall under the Vrishabhavathi Valley watershed region.
“Urban flooding is caused by many reasons include choking of storm water drain with solid waste, encroachment of lakes and drains, discharging sewage flow into storm water drains, inadequate size and opening of pipe across culverts and siltation of drains,” says the study. For the research, these causative factors were represented geo-spatially using remote sensing and Geographic Information System (GIS).
The study was conducted after doing geospatial plotting as well as multiple field visits.
According to the study, in the areas of Timber Yard Layout, Kalidasa Layout, Srinagara Rudrappa Garden, BMK Layout, Vittal Nagara and Azad Nagar, there are problems of very narrow drains, covered drains being encroached upon by small residential buildings and so on.
In industrial areas like N R Garden in Cholurupalya, at flood-prone spots, drains were clogged with plastic waste from factories in the area. “I saw this when I visited the area for field study for the first time. That was six months ago. Now a masonry wall has come up and that has helped bring down floods to an extent,” says Meena.
Cottonpet area in the city has drains closed with cement slabs. “What happens is that the runoff on covered drain does not have any way to drain out. And this leads to flood eventually,” she says, adding that the thickly populated area does not have provision for a municipal drain. There are also instances where the drain is encroached upon by residential buildings which use it as a street, finds the study.
According to the study, in Bakshi Garden, a flood prone zone in the city, drains are again the culprit. “There are drains which are closed using cement slabs, but with small openings through which water leaks, the streets are flooded,” says the researcher.
“In Saneguruvanahalli and Basaveshwaranagar, there are drains which carry so much of silt that the drain beds are now almost at the same level as the road,” she says, adding that at places, there is vegetation inside the drain. “These drains need to be de-silted and cleared of vegetation to prevent future flooding,” she says.
The study finds that one of the reasons that makes Bapuji Nagara flood prone is that a major tributary from Kempambudhi watershed joins the main Vrishabhavathi river here, thus carrying more flow downstream. Heavy rains thus bring in more water than can be handled.
On being asked about the possible solution to the problem, she says reducing the run-off volume in these drains is one thing that can be done as a preventive measure against future floods.
Meena says she hopes the study helps decision makers in assessing and deciding the priority levels of affected areas in future instances of flood, if any.
Credits Bangalore Mirror