Tamilnadu is a highly industrialised state and in future it will become a major IT hub surpasssing the Silicon valley. Lets take the case of Old Mahabalipuram Road. This stretch has n number of IT companies which came up in the past 5- 10 years. Before which it consisted of forests and lakes. With the govt earmarkings of certain areas as Special Economic Zone , IT companies started cashing in along with realtors buying huge plots of land around SEZ for minimal price including lakes/low lying areas. Apartments /leased office building were erected encroaching lakes and ponds with minimal planning for water outflow. This resulted in water getting clogged and ultimately raising water level. 
Secondly , condition was aggravated when Cherumbakkam reservoirs water were released at a stretch which led to unprecedented increase in water level.
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The Brainliest Answer!
The first reason is the cyclone formation.. then the heavy rainfall. ..the rivers were opened and the water drowned our chennai .. but the origin is the cyclone...
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