How do monsoons affect Tamil Nadu?

For Preliminary Examination:  Current events of national and international Significance like Indian Monsoons

For Mains Examination: GS I - World Geography

Context:

The northeast monsoon has kicked in early this year, at least four days sooner for the second year running, over Tamil Nadu. Last year, this phase of the monsoon ended with the State recording 33% more rain than the long-period average, and forecasters expect this year to go the same way.

Read about:

Southwest Monsoon

Northeast Monsoon

Key takeaways:

• The northeast monsoon has arrived ahead of schedule this year, marking its onset over Tamil Nadu nearly four days earlier than usual — the second consecutive year this has happened. In 2024, the same monsoon phase ended with 33% more rainfall than the long-term average, and meteorologists predict a similar trend this year as well.
• Traditionally, policymakers and state administrations have treated surplus rainfall as beneficial, particularly for agriculture and water storage. However, climate change has begun to challenge this assumption.
• Although the total volume of rain has increased, precipitation is now occurring in short, intense, and localized bursts. These concentrated downpours overwhelm the natural and built environment, often causing more harm than good. It is therefore becoming necessary to rethink the belief that “more rain is always better.”
• In urban areas, impervious surfaces such as roads and pavements prevent rainwater from being absorbed into the ground. This results in rapid surface runoff, which can overwhelm stormwater drains and lead to flash floods, waterlogging in low-lying areas, damage to property, and traffic disruptions.
• During such events, as seen in Cyclone Michaung and Tamil Nadu’s floods in 2023, authorities often cut electricity to prevent accidents from loose cables. The large volume of water also triggers sewage overflow, sending untreated wastewater into streets and waterbodies — a major health and environmental hazard.
• The agricultural sector too faces significant challenges from excessive rain. Waterlogged soil suffocates plant roots, washes away seeds, young crops, and nutrient-rich topsoil, thereby reducing soil fertility over time. Moreover, the high moisture encourages fungal infections and pest infestations, leading to lower crop yields and financial losses for farmers.
• Heavy rains can also wash fertilizers and pesticides into rivers and reservoirs, degrading water quality. Standing water after floods provides ideal breeding conditions for mosquitoes, contributing to the spread of vector-borne diseases such as malaria, dengue, and zoonotic infections like leptospirosis and Japanese encephalitis.
• Beyond these immediate effects, prolonged heavy rainfall raises the groundwater table, which can weaken the foundations of buildings, roads, and other infrastructure.
• A persistently high water table exerts pressure on basements, causes cracks, leaks, and mold growth, and reduces the soil’s ability to bear loads. Over time, this can result in structural instability and costly damage.