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ENVIS Technical Report 123,   August 2017
Frequent Floods in Bangalore: Causes and Remedial Measures
Energy & Wetlands Research Group, Centre for Ecological Sciences, Indian Institute of Science, Bangalore, Karnataka, 560 012, India.
E Mail: cestvr@ces.iisc.ernet.in, Tel: 91-080-22933099, 2293 3503 extn 101, 107, 113
Executive Summary

Floods in an urbanised landscape refer to the partial or complete inundation from the rapid accumulation or run-off resulting in the damage to property and loss of biotic elements (including humans). Urban flooding is a consequence of increased impermeable catchments resulting in higher catchment yield in a shorter duration and flood peaks sometimes reach up to three times.  Thus, flooding occurs quickly due to faster flow times (in a matter of minutes). Causal factors include combinations of loss of pervious area in urbanising landscapes, inadequate drainage systems, blockade due to indiscriminate disposal of solid waste and building debris, encroachment of storm water drains, loss of inter connectivity among lakes, housing in floodplains and natural drainage and loss of natural flood-storages sites. Flood mitigation in urban landscape entails integrated ecological approaches combining the watershed land-use planning with the regional development planning. This includes engineering measures and flood preparedness with the understanding of ecological and hydrological functions of the landscape.

Bangalore is experiencing unprecedented urbanisation and sprawl in recent times due to concentrated developmental activities with impetus on industrialisation for the economic development of the region. This concentrated growth has resulted in the increase in population and consequent pressure on infrastructure, natural resources and ultimately giving rise to a plethora of serious challenges such as climate change, enhanced green-house gases emissions, lack of appropriate infrastructure, traffic congestion, and lack of basic amenities (electricity, water, and sanitation) in many localities, etc. This study shows that there has been a growth of 1028% in urban areas of Greater Bangalore across 45 years (1973 to 2017). Urban heat island phenomenon is evident from large number of localities with higher local temperatures. The study unravels the pattern of growth in Greater Bangalore and its implication on local climate (an increase of ~2 to 2.5 ºC during the last decade) and also on the natural resources (88% decline in vegetation cover and 79% decline in water bodies), necessitating appropriate strategies for the sustainable management.
Frequent flooding (since 2000, even during normal rainfall) in Bangalore is a consequence of the increase in impervious area with the high-density urban development in the catchment and loss of wetlands and vegetation. This is coupled with narrowing and concretising storm water drains, lack of appropriate drainage maintenance  works with the changes in enhanced run-offs, the encroachment and filling in the floodplain on the waterways, obstruction by the sewer pipes and manholes and relevant structures, deposits of building materials and solid wastes with subsequent blockage of the system and also flow restrictions from under capacity road crossings (bridge and culverts). The lack of planning and enforcement has resulted in significant narrowing of the waterways and filling in of the floodplain by illegal developments. Causal factors and remedial measures to mitigate impacts of flooding are:

  • Loss of interconnectivity among lakes due to encroachment of drains or dumping of solid wastes, Construction and Demolition (C & D) wastes
  • Encroachment of flood plains and wetlands (construction in valley zones, flood plains and lake bed) and de-notifying lakes (under the guise of ‘dead lakes’ – no lake can be dead as it does the job of ground water recharge)
  • Narrowing and concretising storm water drains impairing hydrological functions of the natural drains
  • Loss of pervious areas - reduction of open spaces, wetlands and vegetation cover
  • Increased paved surfaces in the city (78% paved surface and likely to be 94% by 2020) due to unplanned irresponsible urbanisation by senseless decision makers.

Solutions: Ecological Management of Storm Water Drains and Wetlands to Mitigate Frequent Flooding in Bangalore

  • Reestablish interconnectivity among lakes by removing all blockades (encroachments, solid waste dumping)
  • Protect Valley zones and Buffer regions of wetlands: protect valley zones considering ecological function and these regions are ‘NO DEVELOPMENT ZONES’ as per CDP 2005, 2015
  • Stop narrowing and concretising natural drains
  • Vegetation in the drain takes the load during peak monsoon, there is no need to concretise the channel.
  • Vegetation allows groundwater recharge while treating the water (bioremediation);
  • Drains with vegetation without any bottlenecks (hindrances) would be the best option to mitigate floods.
  • Narrowing channel and concretizing would only increase the quantum of water and velocity, which would be disastrous.
  • Objective should be towards mitigation of floods and not to generate high overland flows (with increased quantum and flow velocity)
  • Experts should think sensibly with holistic knowledge (considering all subject knowledge) than fragmented narrow sectorial knowledge. Advice by pseudo experts would be detrimental as the society would be deprived of ground water, frequent floods and unnecessary livelihood threats.
  • Decongest Bangalore
  • Shift major installations to other cities in Karnataka,
  • Stop further industriaisation and commercial establishments in bangalore.
  • Protect open spaces – lakes, parks, etc.
  • Stop further growth of dying city – with water and oxygen scarcity
  • BWSSB should stop issuing senselessly NOC (no objection certificate) to major building projects as there is not sufficient water in the city.
  • Environment clearance as per the norms of Environment Protection Act (2016), Wetlands (Conservation and Management) Rules, 2016, SWM 2016, C & D Wastes, 2016,   Air act 1981, Water (prevention of Pollution) Act, 1974.

Activities around lakes

Norms to protect and conserve Wetlands

Encroachment of lake bed and loss of interconnectivity among

The Hon’ble Supreme Court in Civil appeal number 1132/2011 at SLP (C) 3109/2011 on January 28,2011 has expressed concern regarding encroachment of common property resources, more particularly lakes (and raja kaluves) and it has directed the state governments for removal of encroachments on all community lands.
Eviction of encroachment: Need to be evicted as per Karnataka Public Premises (eviction of unauthorised occupants) 1974 and the Karnataka Land Revenue Act, 1964

Buildings in the buffer zone of lakes

In case of water bodies,  75.0 m buffer of ‘no development zone’ (as per recent National Green Tribunal direction) is to be maintained around the lake (buffer region to be as per revenue records)

  • As per BDA, RMP 2015 (Regional Master Plan, 2015)
  • Section 17 of KTCP (Karnataka Town and Country Planning) Act, 1961 and sec 32 of BDA Act, 1976
  • Wetlands (Conservation and Management) Rules 2010, Government of India; Wetlands Regulatory Framework, 2008.

Construction activities in the valley zone (SEZ by Karnataka Industrial Areas Development Board (KIADB)) in the valley zone

This is contrary to sustainable development as the natural resources (lake, wetlands) get affected, eventually leading to the degradation/extinction of lakes. This reflects the ignorance of the administrative machinery on the importance of ecosystems and the need to protect valley zones considering ecological function and these regions are ‘NO DEVELOPMENT ZONES’ as per CDP 2005, 2015

Alterations in topography

Flooding of regions would lead to loss of property and human life and, spread of diseases.

Increase in deforestation in catchment area

Removing vegetation in the catchment area increases soil erosion and which in turn increases siltation and decreases transpiration

Documentation of biodiversity

  • The biodiversity of every water body should form part of the School, College, People’s Biodiversity Registers (SBR, CBR, PBR).
  • The local Biodiversity Management Committees (BMC) should be given necessary financial support and scientific assistance in documentation of diversity.
  • The presence of endemic, rare, endangered or threatened species and economically important ones should be highlighted
  • A locally implementable conservation plan has to be prepared for such species

Implementation of sanitation facilities

  • The lakes are polluted with sewage, coliform bacteria and various other pathogens
  • Preserving the purity of waters and safeguarding the biodiversity and productivity, dumping of waste has to be prohibited
  • All the settlements alongside the water body should be provided with sanitation facilities so as not to impinge in anyway the pristine quality of water

Violation of regulatory and prohibitory activities as per Wetlands (Conservation and Management) Rules, 2016 and 2010;
Regulatory wetland framework, 2008

Environment Impact Assessment (EIA) Notification, 2009.
Wetlands (Conservation and Management) rules 2010, Government of India; Regulatory wetland framework, 2008
Regulated activity

  • Withdrawal of water/impoundment/diversion/interruption of sources
  • Harvesting (including grazing) of living/non-living resources (may be permitted to the level that the basic nature and character of the biotic community is not adversely affected)
  • Treated effluent discharges – industrial/ domestic/agro-chemical.
  • Plying of motorized boats
  • Dredging (need for dredging may be considered, on merit on case to case basis, only in cases of wetlands impacted by siltation)
  • Constructions of permanent nature within 50 m of periphery except boat jetties
  • Activity that interferes with the normal run-off and related ecological processes – up to 200 m

Prohibited activity

  • Conversion of wetland to non-wetland use
  • Reclamation of wetlands
  • Solid waste dumping and discharge of untreated effluents

Damage of fencing, solid waste dumping and encroachment problems in Varthur lake series


High Court of Karnataka (WP No. 817/2008) had passed an order which include:

  • Protecting lakes across Karnataka,
  • Prohibits dumping of garbage and sewage in Lakes
  • Lake area to be surveyed and fenced and declare a no development zone around lakes
  • Encroachments to be removed
  • Forest department to plant trees in consultation with experts in lake surroundings and in the watershed region
  • Member Secretary of state legal services authority to monitor implementation of the above in coordination with Revenue and Forest Departments
  • Also setting up district lake protection committees

Polluter Pays principle

National Environment Policy, 2006
The principal objectives of NEP includes :

  • Protection and conservation of critical ecological systems and resources, and invaluable natural and man-made heritage
  • Ensuring judicious use of environmental resources to meet the needs and aspirations of the present and future generations
  • It emphasizes the “Polluter Pays” principle, which states the polluter should, in principle, bear the cost of pollution, with due regard to the public interest

Prevention of pollution of lake

National Water Policy, 2002
Water is a scarce and precious national resource and requires conservation and management.
Watershed management through extensive soil conservation, catchment-area treatment, preservation of forests and increasing the forest cover and the construction of check-dams should be promoted.
The water resources should be conserved by retention practices such as rain water harvesting and prevention of pollution.

Discharge of untreated sewage into lakes

The Environment (Protection) Act, 1986

  • Lays down standards for the quality of environment in its various aspects
  • Laying down standards for discharge of environmental pollutants from various sources and no persons shall discharge any pollutant in excess of such standards
  • Restriction of areas in which industries, operations or processes shall not be carried out or carried out subject to certain safeguards

The water pollution, prevention and its control measures were not looked upon

Water (Prevention and Control of Pollution) Act, 1974

  • It is based on the Polluter paysprinciple.

The Pollution Control Boards performs the following functions :

  • Advice the government on any matter concerning the prevention and control of water pollution.
  • Encourage, conduct and participate in investigations and research relating to problems of water pollution and prevention, control or abatement of water pollution.
  • Inspects sewage and effluents as well as the efficiency of the sewage treatment plants.
  • Lay down or modifiy existing effluent standards for the sewage.
  • Lay down standards of treatment of effluent and sewage to be discharged into any particular stream.
  • Notify certain industries to stop, restrict or modify their procedures if the present procedure is deteriorating the water quality of streams.

Pathetic water scenario and insufficient drinking water in Bangalore

The depletion of ground water and drying up off lakes has affected the water availability to meet the current population. At the 4% population growth rate of Bangalore over the past 50 years, the current population of Bangalore is 8.5 million (2011). Water supply from Hesaraghatta has dried, Thippagondanahalli is drying up, the only reliable water supply to Bangalore is from Cauvery with a gross of 1,410 million liters a day (MLD). There is no way of increasing the drawal from Cauvery as the allocation by the Cauvery Water Disputes Tribunal for the entire urban and rural population in Cauvery Basin in Karnataka is only 8.75 TMC ft (one thousand million cubic – TMC ft equals 78 MLD), Bangalore city is already drawing more water-1,400 MLD equals 18 TMC—than the allocation for the entire rural and urban population in Cauvery basin








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