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‘Zenrainman’ Shares 6 Methods to Cease Floods from Repeating

(Above picture courtesy Twitter/Ashwin Mahesh)

In a single day rains in Bengaluru have left “one individual useless and 75 localities inundated, displacing residents of practically 2,000 flooded homes, marooning 10,000 different residences and damaging 20,000 automobiles”, a Instances of India report notes. These are astonishing figures for a metropolis like Bengaluru following heavy rainfall. 

The worst affected elements have been the japanese, southeastern and northeastern elements of town. In line with the Indian Meteorological Division (IMD), town recorded 13.16 cm (131.6 mm) of rainfall, most of which fell in lower than 12 hours on Sunday evening. This was the third heaviest rainfall town has witnessed in September prior to now 75 years. 

What we noticed on Sunday evening is a continuation of heavy rainfall from final month. In August, town recorded 370 mm, based on IMD. The figures for August 2022 fell just a little in need of town’s document of 387.1 of rainfall in August 1998. 

Regardless of unprecedented rains, the rationale why elements of town are horribly inundated, flooded and water-logged is primarily due to man-made components. 

Talking to The Higher India, S Vishwanath, a civil engineer and urban-regional planner with over three many years of expertise within the water and sanitation sector, discusses why Bengaluru has witnessed such unprecedented floods and the potential options to handle them. 

‘Tyranny of small choices’

In 1966, the American economist Alfred E Kahn wrote an essay explaining a phenomenon he known as ‘the tyranny of small choices’. The essay presents a situation during which a number of choices, individually small and insignificant in dimension and time perspective, cumulatively lead to important outcomes which are each sub-optimal and undesirable. 

Bengaluru, based on S Vishwanath, has reached this juncture of extreme flooding and water-logging due to what he calls ‘the tyranny of small choices’.   

Having labored on coverage groups for writing the State (Karnataka) Water Coverage, rainwater harvesting coverage and bye-laws for Bengaluru and wastewater reuse coverage for Karnataka, he says, “Each particular person act by a landowner to degree a web site, encroach on a stormwater drain or replenish particles right into a lake doesn’t have an instantaneous influence. A person doesn’t assume that it’s an issue in the event that they encroach on a drain. However like that one individual, 50 others are doing the identical factor due to particular person choices taken by the authorities. While you’re immediately confronted with a 120mm a day rainfall occasion, you’ve got a large downside.”

Extra particularly, nonetheless, Vishwanath highlights three key causes behind latest occasions:

1) Local weather disaster is clearly upon us: Now we have a definite enhance in rainfall compounded by the city warmth island impact – brought on by exponential development and concretisation – which creates extra warmth and thus causes extra intense rainfall throughout shorter durations. Usually, town would endure a rainfall depth of 60 mm per hour, however now we’re speaking about 180-200 mm per hour for brief durations. Bengaluru is simply not ready for this type of rainfall depth.  

2) Elements of town worst-affected have comparatively flat terrain: These areas was once previous rice paddy fields. Once we overlaid infrastructure right here, we constructed roads with none cross-drainage works satisfactory for this sort of rainfall. These roads have basically change into dams. 

3) Underinvestment in crucial infrastructure: There are feeder channels that take the water from the floor to a close-by lake or a channel. Throughout agricultural occasions, these feeder channels used to maneuver about relying on which land was cultivated, which lake was getting used and so forth. 

They haven’t been recognized for contemporary necessities of runoff. Due to this fact, governments have underinvested in stormwater drainage infrastructure. To compound that downside, we now have insufficient sewage infrastructure, leaving sewage to drift about in these drainage channels and lakes. 

Sustainable options 

Nevertheless, Vishwanath does imagine that there are each brief and long-term options accessible. 

1) Highway audit: One of many issues we have to do instantly is a highway audit for drainage. The authorities must ask themselves whether or not all roads have stormwater drains on adjoining sides. Are these drains networked? Most drains at this time merely cease at a useless finish. These drains ought to go in a hierarchy and empty right into a lake or a river. Are the cross drainage works satisfactory just like the field culverts and Hume pipes, and might the water transfer from one facet of the highway to the opposite? This sort of audit needs to be carried out for all roads within the metropolis. 

2) Defend stormwater channels: Stormwater channels needs to be lined with concrete in order that they’re demarcated and authorities should guarantee they don’t seem to be allowed to be encroached upon. That community ought to ensure that it disposes of the water lastly right into a river like Vrishabhavathi. 

If a authorities needs to construct a highway or metro station, they purchase the land, pay compensation to the earlier house owners and clear up the house for these functions. 

Equally, the authorities must now purchase land for stormwater drains. The town should pretty compensate those that lose their land, however then they should design the stormwater drains adequately for these local weather change rainfall occasions. This course of needs to be systematic as a hydrological design which is watershed-based. We’ve not been partaking within the course of systematically and as an alternative have been growing the variety of drains on an ad-hoc foundation. 

3) Make investments quickly in sewage networks: We have to saturate town with sewage networks so that each one sewage is picked up and despatched to sewage remedy vegetation (STPs). 

4) Enhance our prediction abilities: The Karnataka State Pure Catastrophe Monitoring Centre has 99 automated climate stations in Bengaluru, which is the biggest density of climate stations for any metropolis in India. Now, they’re excellent at figuring out heavy rainfall incidents and sending a sign out to a given space within the metropolis that it could actually count on floods. 

We have to enhance their predictive powers to a minimal of three days prematurely and ensure that this info is acted upon as quickly as attainable. This can require extra funding within the modelling course of and bettering the automated climate stations. 

5) What can residents, communities and residence complexes do? Folks should make investments closely in rainwater harvesting. We have to ensure that we acquire as a lot of the rainwater as attainable, use that to recharge our aquifers and attempt to design our plots and residences and gated communities as zero rainfall discharge areas. The thought is to carry onto the rain and guarantee its constructive use moderately than letting it run about and flood the place. 

The rainwater harvesting by-law in Bengaluru states that for each sq. metre of roof space, you must create a storage or recharge of 60 litres of water. For each sq. metre of the paved space across the constructing, you should create a storage or recharge of 30 litres of water. 

Broadly, a one-day rainfall occasion of 60 mm may be utterly managed by even a small home not to mention an residence or giant gated communities. 

If the regulation is adopted, we’ll be lowering the influence of flood by an element of three. About 65% of the land use of any specific space is housing or residential. If these residential areas handle rainwater appropriately by way of rainwater harvesting, there will probably be no exterior water to create floods. 

6) Design on a watershed foundation: Each lake is a micro or mini watershed. Authorities should perceive {that a} watershed is a hydrological unit, perceive how water flows and be certain that it’s drained into channels and flows into the lake. When the lake overflows, it connects to the subsequent downstream lake, for which they’ll want sluice gates that they will function. 

In the event you anticipate heavy rainfall, you open up sluice gates, enable the water to move out, and the lake is able to obtain the flood waters and retain it and not using a downside. Primarily, you forestall flooding by taking precautionary motion. If there’s a rainfall occasion which exceeds 60mm, like the continued one, that extra water needs to be drained to achieve lakes that are related to totally different elements of town. 

How can you prevent floods in Bengaluru? Check out this map.
Drainage map of Bengaluru with ridge line (Picture courtesy Central Floor Water Board)

Why is fixing Bengaluru’s flood downside a nationwide situation?

For a metropolis like Bengaluru, it takes a particular form of talent to create floods. 

“The town has a median elevation of 920 metres and cascades down into valleys and rivers on all sides. In contrast to Chennai, Mumbai or Kolkata, this metropolis is on a hill or a ridge line. It calls for excellent incompetence if town can create floods,” argues Vishwanath. 

“Nevertheless, the western or southern elements of town aren’t flooded apart from small pockets the place stormwater drains or lakes have been encroached on. The flood has notably affected the japanese half (its southeast facet) of town. And that could be a peculiar hydrological assemble. It’s a flat terrain with very restricted percolation as a result of the clay layer on the backside doesn’t enable the water to percolate. We should be taught that town isn’t one unit. It contains many models of rainfall and hydrology and we must always design satisfactory infrastructure for context,” he provides. 

One purpose why the latest floods in Bengaluru have garnered such media consideration is that it struck the Outer Ring Highway, which connects town to all the key software program tech and e-commerce places of work. “That’s why there’s such a large public hue and cry. For the reason that floods have straight hit town’s financial engine, there’s all this hullabaloo,” he notes.  

Moreover all of the harm, the continued floods have sparked an uncommon public discourse on-line the place ‘locals’ have began blaming the inflow of migrants for what’s occurring within the metropolis.

Vishwanath says, “However this metropolis can present good employment alternatives to many Indians. That is one thing everybody from Bengaluru needs to be happy with. Commensurate with the worth town generates when it comes to GDP, each the Centre and State should make investments particular funds to construct up the requisite infrastructure and stop these floods. It’s not a local-city downside, however a nationwide one and the authorities want to take a position much more than they’re doing proper now.”    

(Edited by Yoshita Rao)

Further sources: 
’75 areas hit; third heaviest rainfall in September in Bengaluru in 75 years’ by Niranjan Kaggere and Shreyas HS; Revealed on 6 September 2022 courtesy The Instances of India
‘Why Bengaluru was flooded: Encroachment on drains and a vigorous monsoon’ by Aksheev Thakur; Revealed on 5 September 2022 courtesy The Indian Categorical
‘Tyranny of small choices’ courtesy Wikipedia 

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