Drains in City’s North May Not be Able to Bear Flooding

Published: 15th May 2015 06:01 AM  |   Last Updated: 15th May 2015 06:01 AM   |  A+A-

BENGALURU: The drainage system in north Bengaluru, especially in areas between Indian Institute of Science (IISc) and Kodigehalli, may not be able to withstand future floods, says a study by city scientists.

An IISc team comprising R L Gouri and Prof V V Srinivas of the Department of Civil Engineering set out to understand the reliability of an 18-km stretch of storm water drainage network in northern Bengaluru. The network was divided into 34 sub-watersheds for ease of analysis.

To study the network, the duo gathered data on daily and sub-daily rainfall in different seasons for over 20 years, and collected information on the substrate type, land use and land cover for 2006. The collated information was modelled using Storm Water Management Model (SWMM), a technique for estimating the quantity and velocity of flow in drains. Drain width, depth, slope and roughness besides other related parameters were analysed to assess the reliability of the network.

The Method

The team then used reliability assessment methods, and considered three modes of failure that could occur to a drainage network. If velocity of flow exceeds a particular threshold, it could lead to erosion in the drain. But if the velocity of flow is lower than the minimum requirement it could cause silt deposition. Another mode of failure occurs if the runoff exceeds the capacity of drains.  The reliability analysis carried out by the team revealed that most of the drains are prone to all the three modes of failure.

However, the presence of lakes in a drain network enhances its reliability. On possible solutions to improve the reliability of the network, Srinivas said, “Citizens can work towards prevention of encroachment of lakes, and maintaining the  capacity of drains by ensuring that they are free from waste material that causes clogging.”

Redesigning the storm water drainage system by considering the failure modes could help in better management of storm water and reduce the frequency of flooding in the study area.

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