Historical flooding problems in India, Chennai.
Heavy rainfall years have been becoming more frequent in recent decades in India.
As a result, people are also experiencing more frequent occurrences of floods in several parts of the country including Chennai.
These are considered climate change-induced floods/disasters.
Chennai suffered the serious impacts of floods in 2005, 2015 and, again, in 2023.
Each one of these floods is unique, the impact has been devastating, increasing year after year.
The flood in 2023 is considered the worst in the past 47 years.
The coastal city of Chennai has also got to deal with coastal floods and climate change and the consequent impact of seawater rise.
The key issue, is to highlight the necessity to decode Chennai’s urban and peri-urban hydrology.
Make meaningful and scientific interventions not only towards flood mitigation but also towards handling droughts and in building climate-resilient strategies for Chennai and Chennai Metropolitan Area (CMA).
Solutions for flood mitigation,water security,restoring water bodies and prioritizing ecological conservation
Chennai city and the adjoining districts are richly endowed with wonderful watersheds.
There are 3,588 irrigation tanks in Kancheepuram, Chengalpattu and Tiruvallur districts, as highlighted in tank memoirs.
These are man-made but magnificent watersheds created through a series of earthen embankments, constructed across streams which carried heavy flows during the monsoon months.
Unfortunately, these tanks are neglected, silted up with broken bunds and control structures.
In addition, catchment areas, flood plains, feeder and supply channels and even the water spread area in many of these tanks are heavily silted and encroached.
The net result is a double disadvantage: Water storage in these tanks is very little and run-off is very high (over 80%) which caused heavy damage to the city of Chennai.
A comprehensive hydro-elevation (drainage) mapping needs to be drawn up covering the upstream-downstream watersheds with Chennai and the sea.
Chennai is in fact geographically very uniquely placed, which is a blessing.
It has three waterways (rivers) that run through the city, something which no other city in the country and in South Asia can boast of.
The Kosasthalaiyar river runs through the northern part of Chennai.
The Cooum which takes care of central Chennai.
The Adyar which caters to southern Chennai.
Further south, the Palar which carries the flow.
Unfortunately, these major drainage systems are in pretty bad shape due to heavy encroachments.
These rivers have also lost their gravity and velocity due to sludge and silt deposits.
What these waterways need is year-long attention and maintenance and not cosmetic interventions such as river-front and canal front developments.
It is extremely critical to acknowledge the fact that the degree of urban expansion in the Chennai city has been one of the fastest in the country.
It is important to recognise that the urban expansion process is irreversible and can be disastrous if not regulated.
When the city limit was expanded from 174 sq.km to 426 sq.km, and the CMA to 1,189 sq.km, there was very little thought devoted to protecting the ecological hotspots in the expanded areas.
In the process, Chennai has lost many lakes and ponds and much of the Pallikaranai marsh land and coastal wetlands.
At present, the CMA is to be expanded from the existing 1,189 sq.km to 5,904 sq.km covering the entire districts of Tiruvallur, Chengalpattu, Kancheepuram and parts of Ranipet district as part of the Master Plan III.
Chennai city and the CMA can be permanently saved from floods while, at the same time, get round the clock water supply even in a drought year provided the measures indicated above are followed truthfully and scientifically.
This is what is called converting disaster into an opportunity.
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