Why does Bengaluru get clogged in the rain? 5 facts

Bengaluru, Sep 07: Bengaluru, India's Silicon city has flooded again. The record rainfall in August that has now spilled over to September has brought Bengaluru to its knees and exposed the existing chink in the city.

Around 430 houses have been completely damaged in the floods and 2,188 others have suffered partial damage. About 225 km of roads, bridges, culverts, and electric poles have also been damaged. There have been power cuts in certain parts of Bengaluru.

And this in fact is a never-ending sight for Bengaluru. Every year, the same story. Each year, hundreds of crores are spent on fixing roads, stormwater drains and infrastructure.

While extreme rains along with flooding, landslides, and other devastation have become frequent across the world. Be it flooding in Bengaluru or Pakistan, the culprit is the same: climate change.

A study by Karnataka State Natural Disaster Monitoring Centre (KSNDMC) showed that Bengaluru's rainfall patterns have indeed been changing and that it is an indicator of climate change.

The imprints of changes in climatic conditions are in the form of high-impact weather events. The occurrence of Extreme weather events has increased both in terms of frequency and intensity across the state in the last decades.

The data showed that Hydro-Meteorological disasters such as drought, flood, hailstorms, cyclones, heatwave, thunderstorms, and lighting events have occurred in the state more frequently in recent years. The extreme weather events have caused the loss of human life, livestock, critical infrastructure, and private and public property.

The study looked at rainfall data from two periods - 1960-1990 (named P1), and 1991-2017 (P2). It was found that the average annual rainfall in Bengaluru Urban district increased by 13% (or 107 mm - from 836 mm to 943 mm) in the period from P1 to P2.

"The intensity of the rainfall has increased in Bengaluru too. With decreasing open space and ineffective stormwater drains, there is little recharge - most of the water is lost as runoff. So flooding has become quite common," the study said.

Climate change making prediction difficult

According to India Meteorological Department (IMD) Director General Mrutyunjay Mohapatra, the day-to-day rainfall data since 1970, reveals that the number of very heavy rainfall days has increased and that of light or moderate rainfall days has decreased.

"That means if it is not raining, it is not raining. If it is raining, it is raining heavily. The rainfall is more intense when there is a low-pressure system. This is one of the most important trends found in the tropical belt, including India. Studies have proved that this increase in heavy rainfall events and decrease in light precipitation are due to climate change," he told PTI in an interview.

The senior meteorologist explained that climate change has increased the surface air temperature, which in turn has increased the evaporation rate. Since warmer air holds more moisture, it leads to intense rainfall.

"Climate change has increased the instability in the atmosphere, leading to an increase in convective activity - thunderstorms, lightning and heavy rainfall. The severity of cyclones in the Arabian Sea is also increasing. This increase in the frequency of extreme weather events is posing a challenge to forecasters. Studies show that the ability to predict heavy rainfall is hampered due to climate change," he said.

Why Bengaluru chokes every time it rains?

A recent report lists these 5 possible causes behind frequent flooding in Bengaluru:

• Loss of interconnectivity among lakes due to encroachment of drains or dumping of solid wastes, Construction and Demolition 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.

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 greenhouse gases emissions, lack of appropriate infrastructure, traffic congestion, and lack of basic amenities (electricity, water, and sanitation) in many localities, etc.

What next?

Karnataka Chief Minister Basavaraj Bommai blamed the previous Congress governments' 'maladministration' and unprecedented rains in the capital city for the deluge.

He said, despite all odds, his government has taken it up as a challenge to restore the rain battered city, and make sure that such things don't recur in the future.

"Basically the issue lies in two zones, particularly the Mahadevapura zone for reasons such as presence of 69 tanks in that small area and almost all of them have either breached or are overflowing, secondly, all establishments are in low lying areas, and the third is encroachments," he listed out.

Noting that his government has taken it as a "challenge", the CM said officers, engineers and workers and State Disaster Response Force (SDRF) teams are working 24/7.

"We have cleared lots of encroachments and we will continue to clear them. We are installing sluice gates to the tanks so that they can be managed better. I have instructed officials to ensure that the control room works 24/7. We have started dewatering in most of the areas. Other than one or two areas almost all areas have been dewatered," he said, adding that rain is not giving respite to work properly as there have been rains every day.

"Now I have taken it up as a challenge. I have given Rs 1,500 crores for development of storm water drains, I have yesterday released Rs 300 crore to remove all encroachments and do a pucca structure along the storm water drains and for the infrastructure, so that there are no impediments and bottleneck in the flow of water."