Chapter 13Disaster and Hazard Management

13.1 Introduction

Bengaluru has been experiencing very high rates of urbanisation and population growth. Parts of the city are vulnerable to several natural and manmade disasters in varied degrees. Urban flooding, wide spread pollution and scarcity of water are some of the challenges the city faces presently. Certain hazards like droughts, earthquakes etc in other parts of Karnataka also have impact on the city. Hazard and Disaster Management as part of the revised master plan is an attempt to understand the hazards, reduce their impact and decrease the vulnerability of the city to these hazards.

13.2 Hazard Risk Assessment

Hazard Risk Assessment includes identification of the major hazards (natural & manmade) affecting the Bengaluru metropolitan area, understanding the risk the city faces from the hazard, and profiling the hazard and its vulnerabilities. Identification of the major hazards in BMA has been done through past occurrences, frequency and impact levels. The physical, social, economic and environmental vulnerabilities of the hazards have been assessed to prepare strategies to reduce vulnerabilities.

Bengaluru, owing to its location, is not affected by hazards like volcanoes, tsunami and coastal cyclones. The climate in Bengaluru is favourable and it is not affected by extreme temperatures. However, the city is affected by several natural and manmade hazards in varying degrees. Some hazards like earthquake, floods and drought outside BMA/planning area but primarily limited to Karnataka may also affect the city in various ways like in migration from other parts of the state, water scarcity, agricultural scarcity, energy deficit, water deficit and loss of critical supplies to the city. The Hazards affecting the city may be classified into natural and man-made hazards.

Earthquake is a major natural hazard with severe impact and high vulnerability. Bureau of Indian Standards [IS 1893 (Part I):2002], has grouped the country into four seismic zones, viz. Zone II, III, IV and V with zone V being the most seismically active region while zone II is the least. Bengaluru region is located in low seismicity zone (Seismic zone 2). The intervention of the Master Plan is restricted to guidelines that may help reduce vulnerability to an earthquake.

Vulnerability: Since Bengaluru is in a region, prone to low and moderate earthquakes earthquake related environmental vulnerability is less significant. In the event of a medium intensity earthquake in the region, there will be some physical damage to buildings and infrastructures. Economic activities in the city are expected to be disrupted for a short while. There may be loss to life and property depending on the intensity of the earthquake.

Mitigation: To reduce the physical damage, buildings, communication towers and public utility centres, and other critical infrastructure need to withstand damage during an earthquake. Construction rules need to be followed to resist vulnerable condition. All multi-storey buildings must be designed and constructed adopting the norms prescribed in the National Building Code.

Urban flooding is a natural hazard triggered by climatic events, and aggravated by human activities and urbanisation. Flooding of major roads, hinder the functioning of smooth traffic in the city, leads to congestion. In the recent past, incidences of flooding have been reported in 2005, 2007, 2010 and 2013 and very prominently in 2017.

The areas which are particularly prone to flooding include parts of the city which lie within the natural floodplains of the river and drainage channels. Several slums and unauthorised developments in low lying flood prone areas make a large population of the city directly vulnerable to urban flooding. Urban flooding occurs due to natural and manmade factors. Some of the major reasons identified for flooding in BMA are as following.

Heavy and incessant rains: Heavy rainfall event leads to urban flooding. As per the Karnataka State Action Plan for Climate Change, the climate change is expected to affect the rainfall pattern and may lead to several heavy rain events in the future.

b. Increased urbanisation: Increased urbanisation has led to significant changes in the hydrologic flow of storm water runoff from developed areas. Effects of urbanisation like increased peak flow; reduced ground water infiltration and diminishing base flow of streams have impacted urban flooding.

c. Breached water bodies: The loss of retention basins such as lakes and reservoirs has led to increase in the urban flooding. The breached network of natural water bodies and tanks, which play a major role in storm water drainage and runoff within the city, is leading areas getting flooded during heavy rainfall events. It may be noted here that many of the low lying areas are the locations where slums have developed, leaving a large group vulnerable to floods and epidemics. The loss of lakes and streams this also increased the vulnerability of these areas to urban flooding Also, at several locations, storm water drainage system have been broken/ lost due to developmental activities, which is also contributing to urban floods.

Environmental Pollution includes pollution of air, water and noise within the Planning Area.

Air Pollution: Air pollution is a major hazard that has been growing steadily in Bengaluru. The increased number of vehicles on road, industrial activity, construction activity, poor quality of roads and dust on road add to the suspended particulate matter in air. There are more than 67 lakhs vehicles registered in Bengaluru (March 2017). Old vehicles with worn out engines, adulterated fuels, and slow moving traffic lead to increased emissions. The total emissions in 2015 due to vehicular traffic is estimated at 196 tonnes of CO per day, 50 tonnes of HC per day, 9 tonnes of SPM

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per day, and 321 tonnes of NOX per day²³. Reducing the number of private vehicle trips, and increasing public transport share is expected have a positive impact in reducing the emissions due to vehicular traffic. The vulnerabilities of air pollution include people living along the major roads, travellers, pedestrians and especially children and the elderly.

Water Pollution: Pollution of surface and groundwater is prevalent in Bengaluru. The rivulets Arkavathy, Vrishbhavathy, along with the lakes and the natural streams are highly polluted due to inflow of sewage, industrial effluents and municipal waste. The Dissolved oxygen (DO) level in lake waters is decreasing indicating organic pollution load leading to a phenomenon called eutrophication. Untreated Sewage flowing into lakes cause the lake to decay, and loss of aquatic life. The people living around the polluted lakes are very vulnerable as the area in the vicinity of the lake is covered in foul smell emanating from the lake. The froth and smell affects the commuters and the water pollution has led to ground water getting polluted in the area. Ground water in BMA is polluted due to sewage pollution and industrial pollution, over exploitation of ground water resources and high Nitrate concentration in ground water.

Noise pollution: The sources of noise pollution in BMA are a) vehicular traffic, b) flying aircrafts near airports, c) drilling of bore wells, d) industrial sound, e) construction activities, f) DG sets, g) public address systems, etc. Noise sensitive areas like hospital area, schools and also residential neighbourhoods are witnessing heavy noise pollution due to traffic and unnecessary honking.