Urban Floods:
Case Study of Bangalore
T. V. Ramachandra 1 and Pradeep P. Mujumdar 2
1 Energy & Wetlands Research Group, Centre for Ecological Sciences, 2 Department of Civil Engineering,
Indian Institute of Science, Bangalore – 560 012, India

Strategies for the future

Strategy to incorporate Integrated Storm Water Management (ISWM) approach to flood management integrating land and water resources development in a lake catchment or river basin, within the context of integrated water resources management, and aims to maximize the net benefit from floodplains and to minimize loss to life from flooding.
This is based on

  • a participatory approach involving users, planners and policy-makers at all levels and should be open, transparent, inclusive and communicative.
  • Decentralization of decision-making is necessary, with full public consultation and involvement of stakeholders in planning and implementation.
  • Coordination at the highest level to promote coordination and cooperation across functional and administrative boundaries needs to be ensured.
  • Land use planning and water management are combined in one synthesized plan, through coordination of land and water management authorities to achieve consistency in planning.
  • Clearing all encroachments that come in the way of the storm water drain network in the city.
  • Restoring all lakes. Removal of all encroachments in lake catchments
  • Declaring 500 m around the lake as no activity zone
  • Aligning the drain network and checking blockage and overflowing of drains.
  • Reviewing existing storm water drains, ensuring connectivity of primary, secondary and tertiary drains.

Redesigning for current load conditions along with building barriers between roads and open drains at crossings.

Thus, an integrated approach to stormwater management maintains the traditional function of minimising flooding,  in addition to integration of water quantity and quality management policies and practices  with the coordinated, total catchment approach to the issues of stormwater management.  In addition to flood management, a primary goal is to protect downstream water bodies from contamination and erosion, while maintaining, or in some cases re-establishing, natural waterways and wetland features as part of the drainage network. The location and design of significant stormwater management infrastructure (e.g. drainage corridors, culverts, etc.) is to be based on a firm understanding of the local needs/values, legislative requirements and practical constraints considering  the hydraulic, hydrologic, environmental, economic, social, legal and practical aspects. For example, maintaining or improving the natural conditions of a waterway in Bangalore (i.e., widening and grading the banks) instead of channelising and concreting, could bring multiple benefits including flood mitigation, water quality improvement by vegetation and recreational benefits. Suggested strategic actions are outlined in Table 10.

Table 10 – Strategic Actions

Proposed Actions How Possible Implementation Mechanisms
Integrated catchment based management and planning to improve catchment landuse and drainage conditions Developing Catchment and Stormwater Management Plans (CSMP) to integrate all stormwater issues on catchment levels including: Water quality, flooding, waterways, assets management and funding, planning and development control, and other environmental and social issues. More details on typical CSMP’s contents, objectives, and outcomes are presented in section 8.2 of this report. Catchment and Stormwater Management Plans  should be developed for each major catchment. Significant coordination between all stakeholders is required.  This study would require multi-disciplinary team, with expertise in hydrology, environmental, planning and socials issue.
Enforce best practice guidelines as conditions to issuing permits for new or reconfiguration of developments This should include guidelines for:
  • Erosion and sediment controls
  • Setting Floor levels above designated floods)
  • Restrictions on filling in the floodplain and obstruction to flow
  • Legal point of discharge and connection to storm water and sewerage systems.
  • Storm water quality objectives and treatments prior to discharge.
  • Preferred subdivision layout in relation to storm water assets.
Accountability of the agency to ensure implementation of best practice information
Stormwater management solutions to the overall urban water cycle and water conservation strategy
  • Encourage and promote “water sensitive urban design” for maximising infiltration, treatment of stormwater runoff by grass strips, reduction in paved areas in new developments.
  • Rehabilitate and maximise the use the remaining waterbodies to reduce flooding through retardations and to maximise infiltration to groundwater by retaining floodwaters in these basins.
  • Maintain (where possible) the natural conditions (i.e.; unlined) of the channels and waterways to maximise infiltrations to groundwater and also to treat water quality.
The BMP should develop and promote best practice design manual for urban developments and implement these options in the development of the flood mitigation strategy.
Regular water quality monitoring  in major waterbodies through a network of educational institutions  This helps to establish base line data, assess the impacts of land use changes and management practices on water quality, and provide instructions for water usage and human health purposes.
  • Review the conditions and the importance of waterbodies
  • Identify priority areas
  • Determine the type and frequency of monitoring required (this should include average values and events monitoring)
  • Develop and undertake program for storm water quality monitoring
The key objective is to monitor improvements rather than to confirm existing conditions are poor.
Minimise flooding Identify educational institutions to undertake at regular interval drainage and flood studies for the city to: Identify existing drainage system and flood prone areas.
  • Develop overall flood mitigation strategy for the city.
  • Prioritise and undertake the mitigation works based on flood risks.
  • Control new developments, which may impact on flooding.
Develop centralised infrastructure database with a network of instituions.BMP currently embarking on major flood study,Flood mitigation options and strategy will need to be coordinated and endorsed by a number of other authorities to cover issues such as land resumption, planning, changes in sewerage system.
Establish designated flood levels along the main waterway, to provide guidance for new developments or reconfiguration of existing developments.
  • Determine flood profile for the high flood levels (say 10, 20 or 50 years ARI) from the t drainage study
  • Use new survey and contour maps to plot the extent of the flood levels along the waterways.
  • Use GIS based technology to develop a spatial database with web based information systems.
BMP to develop and maintain spatial information systems
Protect the remaining waterways corridor from encroachments of new developments
  • Identify preferred waterway corridor width based on the above high flood levels and other planning and environmental factors.
  • Incorporate the corridor in the Comprehensive City Plan as designated areas for new or reconfiguration of developments. 
As part of the review of the City Plan, the BMRDA, BDA in conjunction with the BMP should incorporate the designated corridor area into the plan.
Minimise sewage inflow to storm water
  • Separation/ relocation of the sewerage system from stormwater system
  • Implement the Sewerage Master Plan including treatment plant upgrade.
  • Enforce/develop planning laws on illegal connections.
  • Develop and upgrade guidelines on sewer construction and maintenance
Establish coordinating committee/taskforce between BWSSB and BMP to coordinate these issues and to undertake an option study (risk, cost, constraints)  to identify the preferred option to separate the two systems. It is may be cost effective to incorporate this option investigation study into the BMP current drainage study. The BWSSB may provide additional funding to this component of the study.
Integrated Municipal Solid Waste Management Adoption of an appropriate strategy is essential for any improvement in the storm water quality and quantity in Bangalore. Implementation to conform MSW Rule, 2000.
Community education programs to improve understanding of the important of clean drainage and waterways Raising community awareness and understanding of the risk of flooding, the importance of clean waterways and its role of supporting the community well being, health and the overall life style in the City of Bangalore.  with numerous successes around the world. This can be undertaken in various forms:
  • Environmental education at schools and colleges
  • Education through mass media
  • Encouraging the community to be involved in catchment care groups
  • CBD and NGO’s to devlop and implement catchment management plan.
  • Schools and colleges
  • NGO’s and CBO’s
  • BMP

 The storm water system consists of many natural water-bodies and a high-density waterway system.  Sewage contamination leading to eutrophication of waterbodies would result in a major health and socio-economic disaster for the city. Some receiving waterbodies have no major outlets and pollutants are accumulated in the sediment deposits. Litter, discarded building materials, sediments and other solid waste items are the main causes of blockages of the drainage system resulting in flooding in some pockets of Bangalore.

The objective of Catchment and Storm water Management Plan is to integrate all water quality, quantity and waterways issues from a catchment perspective to enhance and stabilise degraded waterways, minimise flood risk, maximise amenity and property values and improve water quality in the stormwater system with the following objectives:

  • Prevention of   raw sewage from entering the stormwater system;
  • Promotion of best management practices to improve stormwater quality;
  • Management of storm water drainage  ensuring the protection of waterways, water quality and minimising floods;
  • Integration of water quality management with flooding and waterway corridor management issues;
  • Design and implementation of flood mitigation schemes (where necessary) to minimise the impacts of large flood events and potential damage costs;
  • Mapping and monitoring of  flood prone areas and flood levels along the waterways under appropriate Average Recurrent Interval  storms through drainage and flood studies. Based on the designated flood levels along the main waterway system, waterway corridors are to be determined and to be incorporated as “no development” areas into the City Comprehensive Development Plan to prevent development within these corridors.
  • Alteration in topography in the catchment area to be banned through an appropriate legislative measures;
to provide and coordinate an information and education program for the community and  schools to improve understanding of the risk of flooding, the importance of clean waterways and their role in supporting the community well being, health and the overall lifestyle in the City.  The objective should be to achieve increased community involvement in waterway care.

Citation: Ramachandra T. V. and Pradeep P. Mujumdar, 2009, Urban Floods: Case Study of Bangalore, Journal of the National Institute of Disaster Management, Vol. 3, No. 2, April 2009, pp. 1 – 98.
* Corresponding Author :
  Dr. T.V. Ramachandra
Energy & Wetlands Research Group,
Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560 012, INDIA.
Tel : 91-80-23600985 / 22932506 / 22933099,    Fax : 91-80-23601428 / 23600085 / 23600683 [CES-TVR]
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