A new Zonal Drainage Master Plan (ZDM) for Bengaluru is being prepared as part of the World Bank-supported Water Resilient Project implemented by the Greater Bengaluru Authority (GBA).
However, the absence of reliable data on stormwater and sewage network and the poor management of sewerage networks by various civic authorities are likely to make this task difficult for current planners and implementing authorities.
“Bengaluru currently lacks a robust stormwater drain and sewerage network, which is a major contributing factor to the city’s frequent flooding. The ZDM will not only help address existing gaps but also assess and plan for future challenges,” said a GBA official monitoring the project.
A comprehensive plan
The ZDM will serve as a comprehensive plan for the management of stormwater and drainage systems across Bengaluru or within the jurisdiction of the GBA. “The development of the new ZDM will involve evaluating the existing sewerage infrastructure, identifying gaps and vulnerabilities and designing targeted solutions to increase the efficiency and resilience of the network,” a source told The Hindu.
The exercise will include detailed mapping, analysis of rainfall and runoff patterns, and recommendations for upgrades and maintenance. A key part of the plan will be the creation of an integrated map combining natural and man-made drainage systems, land use and topographic features. It will also include flood risk assessments and strategies in line with future urban growth and development.
While the project builds on IISc Bengaluru’s existing flood mitigation model, the ZDM will act as an extension of it. As reported by The Hindu earlier, the Karnataka State Natural Disaster Management Authority (KSNDA) will work closely with IISc and IIT Madras to implement the project.
CSTEP and WELL Labs, which provide services under a non-profit MOU, will support GBA in specific areas of ZDM. WELL Labs will focus mainly on ZDM preparation, while CSTEP will deal with risk analysis.
Not the first
However, this is not the first time such a plan has been proposed. In 2022, the then Chief Minister Basavaraj Bommai announced a similar initiative prompted by a 2021 CAG audit of Bengaluru’s stormwater management performance. The audit pointed to the absence of a robust policy for stormwater management, noting that “the state government and the BBMP have not considered urban surface runoff as a water resource despite growing water scarcity in the city and the state”.
Four years have passed since that announcement, yet the situation has not improved. This time, however, the civic body has no choice but to act, as the World Bank will release funds based on the results of implementation, a process known as Disbursement Linked Indicators (DLIs).
Not an easy road
However, the task before the GBA will not be easy. There is a significant data gap on stormwater drains and their network across the city. Historically, various parastatal agencies have carried out drainage-related projects independently, without coordination, data sharing or documentation exchange with other civic bodies. Many of these project files have since disappeared, a problem identified in the CAG report. As a result, GBA must now rely on more fragmented sources to obtain critical information.
According to a source involved in the project, crowdsourcing and citizen participation in data collection could be an effective approach. However, the final decision to adopt this strategy has yet to be made.
Published – 23 Oct 2025 19:06 IST
