Why does Velachery in Chennai flood so easily every monsoon?

Ayaan Paul
Ayaan PaulDec 06, 2023 | 16:08

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. 

  • 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. 

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.

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.

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.


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.

Last updated: December 06, 2023 | 16:08
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