Why does Velachery in Chennai flood so easily every monsoon?
As Chenai grapples with its annual tryst with monsoon rains and subsequent flooding, one such residential suburb that has been making waves on social media, deeply affected by this seasonal deluge, is Velachery.
Chennai in deep water
The city experiences a tropical wet and dry climate, characterised by a distinct monsoon season from mid-September to mid-December, driven by north-east monsoon winds. This period brings a substantial amount of rainfall, vital for replenishing water reservoirs but often accompanied by challenges such as flooding.
Velachery, covering an area of approximately 6.82 square kilometres and accommodating a population of 143,991, faces recurrent flooding during the monsoons.
Quite tragic scenes in Velachery , pallikaranai area. Many are stranded with water levels upto 15 ft in a few areas. We got a distress call from a family where an old and ailing woman needed emergency rescue, unfortunately she passed away by the time we reached her. pic.twitter.com/MqIZS8TYML
— Shravan Krishnan (@KrishnanShravan) December 5, 2023
- Known for its hard rock terrain, Velachery contends with a combination of geographical, geological, and urbanisation-related factors that contribute to its vulnerability to heavy rainfall.
- The neighbourhood's experience with flooding underscores the broader challenges many urban settlements in the city face in balancing development with environmental resilience.
#Chennai: Please please bring maximum
— Srikkanth (@Srikkanth_07) December 6, 2023
Attention to this.
Two persons trapped inside a 40 feet trench dug up for a construction site in Velachery since Monday morning.
No sign of rescue till now. Unable to pump out the water. pic.twitter.com/XFcLiZiPNA
Understanding the intricacies of Chennai's monsoons and the specific issues in Velachery sheds light on the complexities of managing the city’s infamously tedious urban water systems in the face of climatic variability and rapid urban expansion.
My friend, his wife & Kid - 2yr old boy is struck here - Area behind Chennai silks #Velachery. As I reach this place & try to call him even network doesn’t support only. This is bad. Darn, Network providers should fix this issue first 🙃😤 @chennaicorp Please drain out ASAP pic.twitter.com/LX0aWmVmoE
— PG Things (@PG_Things) December 5, 2023
Several possible factors contribute towards Velachery’s unfortunate yearly inundation:
Geographical and geological factors
Velachery is situated on a flat coastal plain, characterised by hard rock terrain. The Velachery lake, once spanning 250 acres, and nearby marshlands played a crucial role in natural drainage. However, urbanisation and development have led to the reduction of these water bodies, impacting the area's ability to absorb excess water.
Urbanisation and infrastructure development
Rapid urbanisation in Velachery has resulted in increased impervious surfaces, such as roads and buildings. This hinders natural drainage and exacerbates flooding during heavy rainfall. The hard rock composition of the area also slows down rainwater percolation, contributing to waterlogging.
Indian Air Force choppers flying low over Velachery #chennai, dropping food & water at apartment rooftops..
— Sidharth.M.P (@sdhrthmp) December 6, 2023
4 x Chetak helicopters covered 8 locations across North & South regions of the city& dropped 400kg of essential supplies#ChennaiFloods #chennairain #chennaicyclone… pic.twitter.com/JgHS9fhl22
Inadequate stormwater drainage systems
The existing stormwater drainage systems in Velachery may be insufficient or poorly maintained. In particular, the overflow of Velachery lake, as seen in recent incidents, indicates challenges in managing excess water.
The slow drainage of water is attributed to the discharge of floodwater, with drainage routes leading to Pallikkaranai swamp and Okkiyam Madavu.
Encroachment and land use changes
Encroachment on and around water bodies and changes in land use patterns further reduce the natural drainage capacity. The filling of lakes and marshlands diminishes the area's ability to handle excess water, contributing to inundation in places like Tansi Nagar.
The name clearly says it's Velachery Eri = Lake!
— ஏட்டிக்கு போட்டி | Yaettikku Potti (@diveyalan) December 5, 2023
Lake meaning water logging area! That's all.. pic.twitter.com/r3QLqglIP2
Climate and weather patterns
Chennai experiences a tropical wet and dry climate, with the majority of its rainfall occurring during the north-east monsoon season. Cyclones such as the current Cyclone Michuang in the Bay of Bengal can also impact the region. Changes in climate patterns, coupled with extreme weather events, may lead to more intense and prolonged rainfall, worsening the flooding situation.
Ineffective drainage channels and canals
The efficiency of canals and drainage channels in directing water away from residential areas is crucial. If these channels are choked or inadequately designed, water can stagnate, contributing to the rising water levels experienced in Velachery.
As observed by local residents, the reverse flow of water and the failure of water to drain adequately can be linked to factors such as excess water discharge from Adambakkam lake and Velachery lake. Issues with canals that are supposed to direct water to the Pallikaranai marsh also play a role in the flooding.
Addressing the flooding issues in Velachery necessitates a multi-faceted approach, including sustainable urban planning, improved stormwater drainage systems, preservation of water bodies by the Greater Chennai Corporation.
The confirmed death toll in Chennai has risen to eight as a result of the unprecedented flooding. Officials reported that over 18,000 individuals were displaced and relocated to relief camps across the city. The flooding was initiated by Cyclone Michaung, which commenced its landing between Nellore and Kavali in Andhra Pradesh on Tuesday afternoon.