Bengaluru Floods - Could this have been prevented?
-Amalgrain Studio
Since the past week(4-8 Sept 2022), Bengaluru’s IT hub is tackling one of the worst magnitude of disasters the city has ever seen. It has crippled the city and its infrastructure, causing great hardship and a massive financial loss to all its stakeholders. Sunday’s rains (4th Sept 2022) is estimated to have caused over Rs.225 cr damage to the residents/ occupiers of ORR, Bangalore. [Data source: Indian Express]
Even though the IT hub of Mahadevpura is one of India’s highest tax-paying regions, its local infrastructure and facilities are abysmally poor. The recent rain and floods have raised concerns among all its stakeholders. The floods have also claimed the life of a young individual commuting back home during the harsh weather.
[Image: by Amalgrain - Floods in Mahadevpura]
On the other hand, parts of Bengaluru have faced water shortages and lack of potable water during the same period. The reasons vary from lack of water consumption planning to improper water infrastructure.
A classic case of “Water Water everywhere and not a drop to drink”. [Samuel Taylor Coleridge]
Are these floods natural disasters or man-made?
Our study shows evidence of both aspects at play.
Detailed Problem Statement:
Urban Flooding - Pluvial Flooding:
The primary reason for floods in cities like Bengaluru is often Urban Flooding. Urban Flooding is a consequence of increased impermeable catchments and rapid urbanisation. Water tends to flow to lower grounds without percolating at the point of incidence. Unplanned and haphazard growth has changed the usual direction of water flow causing larger empty spaces like roads and basements to flood.
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[Image: Analysis by Amalgrain - Grey-Green ratio/ Urbanisation - Agara Basin]
[Image: Analysis by Amalgrain - Grey-Green ratio/ Urbanisation - Belandur Basin]
The above images show how Bengaluru has rapidly urbanised in the last 2 decades. The stormwater channel is contracted to make space for urbanization and low-lying catchment zones are reclaimed for built infrastructure.
It is observed that the water runoff from the city is extremely high and only a very limited amount of rainwater incident is used or percolated into the soil.
In a scenario of rain surge, the existing water channel swells and makes its way into low-lying zones causing havoc.
[Image: Analysis by Amalgrain - GIS Analysis for water catchment and flow]
The Water channel(Rajakaluve) connecting Bellandur to Varthur on Sunday saw over 20 Lakh liters (Approximately 600 Tankers worth) of water gushing through it in a matter of few minutes. The situation got worse as the rest of East Bengaluru's surface water made its way into this basin.
But why the sudden water surge?
Climate Change:
Over the past decade, we have noticed widespread effects of Climate change. Erratic weather pattern and sudden shift in the climate has taken the city's infrastructure and administration by surprise.
[Image: Rainwaterharvesting.org - Average monthly Rainfall 1981 - 2005]
This week, we received over 600% of the average rainfall of September in just a mere 4 hours leading to the city infrastructure being overwhelmed with surface water. Most lakes in the city breached their boundaries and started to swell into other neighbouring sectors. However, even after 5 days of this incident, we still notice water-logging in several regions of the city.
Why isn't water flowing out? Why are the roads still flooded?
Inadequate City Infrastructure or the lack of civic sense?
Monday morning as the IT crowd tried to make its way to work, it was welcomed by a water-logged ring road making it close to impossible for one to navigate through. The 5-hour-long traffic jam led to massive losses for major players in the IT sector. [Data source: Deccan Herald]
[Image: Times of India- Overflowing Drains]
We observed the areas with significantly higher elevations were also flooded due to overflowing drains, clogged gutters and back-push of water through stormwater drains. The lack of maintenance and the ignorance of the general public towards city infrastructure has added to the non-functioning of these surface water drains.
[Image: Deccan Herald - Garbage in the Rajakaluve near Agara Lake]
Improper disposal of garbage and overflowing trashcans have made their way to drains during heavy rainfalls and have clogged them. We have observed unsuitable construction of drains and improper disposal of construction waste has also aided in clogging these drains.
Encroachment - a High Risk Zone
Rajakaluve - Bengaluru once had a series of water bodies linked to each other forming a network of water reservoirs, lakes and wetlands. This ensured a system of groundwater replenishment and at the same time, cater for excess water runoff to flow from the higher zones to low-lying zones. The clear path of water flow between these water bodies was called rajakaluve. The Rajakaluve is an essential feature that acts as Bengaluru's surface water drains. Unfortunately, as most of these wetlands and water bodies have dried, a lot of rajakaluves were encroached on along with several low-lying areas and wetlands.
[Image: Analysis by Amalgrain - High flood risk zones with infrastructure]
What were once unplanned and unsanctioned settlements are now high flood-risk zones. Several such land parcels were part of a systematic land grabbing by builders and developers. Building retaining walls and reclaiming the land, at best, can only put a stop to the immediate problems. During surges like last week, water is seen to breach these boundaries and make its way into these settlements.
How can city council and Urban designers step-up to prevent recurrence of such events?
Encroachments must be tackled on a city council level. Laws to protect wetlands and waterways must be enforced by local authorities.
A study needs to be commissioned to identify areas with a fair amount of surface water and aquifers vis-a-vis dry areas solely dependent on aquifers. This should form the basis for the Cauvery water supply and distribution system. The authorities could look at creating a network of Open Wells and bore-wells in areas with an abundance of surface water, along with a good rainwater harvesting mechanism, through law enforcement.
Rajakaluves need to be reclaimed. All the built structures in the path of these water channels need to be removed to avoid any obstruction in the flow of water. We must stop concretizing the earth and narrowing the water channels as it only aids in its increased water velocity, reduced percolation and subsequent flooding during such deluges. All infrastructure must be sensitive to local context and must take into consideration its relation to natural elements.
[Image: Proposal by Amalgrain - Soften and reclaim the Rajakaluve Edges]
Natural resilience will play a huge role in tackling this problem. Human intervention must aid in creating this natural ecosystem. For this, the walls of the rajakaluves need to be softened. The banks can grow vegetation, creating an Urban Forest. This will not only aid in the greening and revitalisation of these areas but also act as a buffer to mitigate such floods during water swellings. The Vegetation will aid in groundwater recharge through the rajakaluve. It will also aid in developing a green belt with space for flora and fauna along its banks.
[Image: Xigan Canal - Water Canal as a social and ecological space]
Due to excessive land-concretization, Bengaluru is left with limited areas for water to percolate. If we find ways to capture rainwater at the point of incidence, we can reduce the amount of surface runoff to the low-lying zones. Residents in the city can harvest rainwater from their rooftops and store it for personal use, while the rest of the water on the site can be diverted to a rain garden for groundwater recharge. This will also be an opportunity for us to reduce our dependence on Cauvery water.
Conclusion
The only way we can stop a repeat of such incidents is through contextual planning of city-level water consumption and distribution systems, urban-level Architectural and Landscape interventions, following strict law enforcement for land usage and a shift in public mindset towards effective and efficient usage of natural resources. The city council must consult field experts while planning and granting permissions for infrastructure development and usage.
By Amalgrain Studio Team:
Ar. Adish Siddapur Matada
Ar. Nikhil GM
PG Neeraja
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