BANGALORE FLOODS
Source: The Hindu
Context
Bengaluru Urban and Rural, Ramanagara, Chikkaballapur, Kolar and Tumakuru are among the 11 districts that have received large excess rainfall, with departures as high as 230 per cent.
Key points
- The recent bouts of rainfall have already battered Bangalore and its surrounding districts.
- Roads, highways and tech parks are inundated and homes are flooded, critical infrastructure such as power and water pumping stations are waterlogged and lakes are overflowing.
- In the last few years, many parts of Karnataka have received excess rainfall during the monsoon season and there have been variations in rainfall patterns in traditionally dry regions.
- This year, the State registered only a 21 per cent departure from the normal between June and August.
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The monsoon rain this year is the second highest that Bengaluru has seen since 1971.
The rainfall of September 4 (131.6 mm) was the third highest single-day amount that Bengaluru has ever recorded.
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- In the Ramanagara district, thousands of residents living in the low-lying area of Ramanagara and Channapatna towns have been struggling to cope with torrential rainfall, with several residential areas inundated.
- Everyone agrees that flooding in this drought-prone region is unprecedented.
Overflowing water bodies
- Rivers reduced to insignificant streams in recent times have suddenly sprung back to life now.
- The water destroyed walls and gushed inside the houses. It even damaged the shutters of shops, Cars, autos and bikes floating in the water.
- It took days for the people to clear the silt that has entered their homes. Excess rain has ruined almost all crops.
| The intricately connected lake system in Bengaluru has seen major disruptions over the years with the proliferation of infrastructure and housing projects and industries also saw many lakes breach bunds. |
- Even before the onset of the monsoon, most of the lakes were full. Due to heavy rain, the water overflowed.
- In the Ramanagara district, most of the 1, 490 lakes and other water bodies have been overflowing. Some have even breached their bunds.
- More than 90 per cent of the 102 lakes that spread over 100 acres each were overflowing in the district.
- Major rivers such as Arakavathy and Kanva have been flowing to the brim.
River pollution
- The gushing waters of the Arkavathy river, a tributary of the Cauvery.
- This water was earlier used for drinking and washing clothes and now it was not used for agriculture it contains chemicals discharged by industries
- The river water carries rainbow hues due to chemical pollution and it is known as a perennial river.
- People from other areas used to come to fetch drinking water from the river, Today the same people buy drinking water for 5 rupees a can.
Irrigation system
- In Channapatna taluk, the lakes had dried up and started receiving water supply from the lift irrigation system.
- Lakes have been receiving water since 2014 and the agricultural sector has benefited a lot over the years.
Water supply to Bangalore
- Bengaluru Urban and Bengaluru Rural and the release of water from reservoirs increased the flow.
- The machinable dam started receiving over 4, 000 cusecs of water from the T.G. Halli reservoir.
- The water-holding capacity of Machanbele is one-third of the T.G. Halli reservoirs.
- T.G. Halli reservoir was opened to let out water after 30 years, water from the reservoir has not been supplied to Bengaluru for years.
- This is because a new project to counter excess pollution in the water will take a few more months.
- After this is done, water (3.4 MLD or Minimal Liquid Discharge, capacity) will be supplied to 10 -15 per cent of the city from T.G. Halli again.
Reasons for dying rivers
- Ashoka Trust for Research in Ecology and the Environment a non-profit organisation in 2015, examined why the Arkavathy was drying up.
- Reasons for the major cause of the dying of the river.
- A decline in inflows to the T.G. Halli reservoir due to the decreased rainfall.
- Many of the blockages in river channels were check dams built by various government departments.
- Drop in the water table due to intensive groundwater use, mostly for agriculture and
- The presence of eucalyptus plantations on the T.G. Halli catchment.
Climate projection
- The multi-model climate projection shows that rainfall is expected to increase by 10-25 per cent in the districts of Karnataka by the mid-2030s.
- Most of this will occur within a few days. when high-intensity rainfall gets more run-off.
- The water cannot infiltrate into the ground fast enough. Water needs a path out to be expected.
Watershed management
- Some innovative watershed interventions in the Arkavathy basin by volunteers of agencies have helped in water retention by the catchment and made water available to the local community.
- Recent good rainfall and the aberrations (high-intensity rainfall) have helped us receive the required water.
- Innovative watershed management has helped in retaining water in the catchment.
- This emphasises the need for innovative (ecological and engineering) solutions to manage watersheds.
Climate changes
- It is time it is accepted that there are changes in the climate.
- High-intensity rainfall and issues such as frequent depressions and cyclones point to this.
| Studies have confirmed that enhancing the recharge capabilities of the catchment by maintaining sufficient open spaces and green spaces with native species, decentralised rainwater harvesting and wastewater treatment and reuse would help in meeting the water requirement. |
- This will not burden the exchequer or lead to the wastage of public money.
- Unfortunately, large-scale projects are being pushed by vested interests to pilfer public money.
Work at a glacial pace
- Within Bengaluru city, the impact of poor management of projects is evident, as lake breaches have left many parts of the city marooned.
- The Bangalore Development Authority (BDA) had taken up rejuvenation works of two of the largest and most polluted lakes, but the pace has been slow.
- Officials say heavy rainfall during the summer had slowed down de-silting.
- Bellandur lake, spread over 916 acres of land has 32,33 lakh cubic meters of the slit, of which 13.26 lakh cubic meters have been removed.
- Varthur lake is spread over 434 acres and has 15.10 lakh cubic meters of silt, of which 11.11 lakh cubic meters have been removed.
Saporlite and urbanisation
- Most of the flooding in Bengaluru is seen in the Ponnaiyar river catchment area.
- The soil and chemically altered product of parent rock (Saprolite) are also highly clayey.
- Because of this, geohydrological rainwater infiltration cannot happen.
- Only 3 per cent of the water gets infiltrated in this soil condition.
- The growth of urban jungle in this area over the years further deteriorated rainwater infiltration.
Stormwater drains
- The irrational urbanisation in areas around these lakes has resulted in the deterioration of original stormwater drains.
- The length, width and depth of these drains have reduced over decades.
- The perennial flow of sewerage water, whether treated or untreated, has shrunk the containing capacity to a great extent.
- Even today, more than 1200 MLD of sewerage water flows in these storm water drains.
Using Rainwater
- As all the natural channels are obstructed, the water cannot flow when it rains.
- To undo the damage, the sewerage water has to flow in separate drains and be treated.
- Recycled water should be redistributed at least for non-drinking purposes.
- At present, rainwater is getting polluted with sewerage water.
- Though there is scope for using rainwater, authorities are not seriously considering it.
- Clearing encroachment and obstruction to storm water drains and proper maintenance of lakes will help in the utilisation of water resources.
Encroachment of water bodies
- Though torrential rains are being blamed as a prominent cause of flooding.
- There has been a growing demand to clear encroachment of water bodies by allowing the free flow of water.
- The National Highways Authority of India too criticised for implementing a flawed design and blocking the Waterways.
- At the Sangabasappana Doddi underpass of the expressway, vehicles were submerged and lifted with the help of cranes.
- There have been instances of under-construction toll gates getting flooded and water flowing over the newly built highway near Kumbalgod, Kaniminike and other areas.
- Flooding of roads at various stretches also forced the district administration to divert traffic.
- They also maintain that they are working with other departments to fix the problem.
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The district administration has said that encroachments of the water bodies will be cleared based on Survey of India aerial surveys.
Once the survey is over, it will be superimposed with the village map to identify the extent of encroachment of water bodies in the district.
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Hydrologic regime
- This is a classic example of poor infrastructure design, deliberately ignoring the hydrologic regime in the locality.
- Alterations in the hydrologic regime and disruption of the path of water have aggravated the situation.
- Bureaucrats and engineers conveniently came up with the theory of "lake breach" to hide their inefficient and illogical designs and implementation of the project.
Conclusion
- The need for predictable models Specifically for Bengaluru integrating water, wastewater, flood water and groundwater.
- Need to better inter-agency coordination.
- Identifying the mismatched incentives and short-sightedness.
- Builders have incentives to cut costs and bureaucrats have incentives to favour large-scale projects that create avenues to earn kickbacks.
- As floodwaters ebb and the current misery is a distant memory, policymakers and administrators have their tasks cut out.
Prelims & Mains Perspective
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For Prelims: River pollution, reasons for dyeing rivers, climate changes
For Mains: Explain Banglore floods through the prism of the Cauvery river drought (250 words)
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