Anatomy of Delhi Rainfall Events: What Exactly Happened on June 28th?

Delhi recorded 228.1 mm of rainfall on Friday, the highest in the last decade. This extreme weather event highlights the vulnerabilities in the city's infrastructure and its inability to handle such massive rainfall. In this article, we delve into the unprecedented rainfall event that struck Delhi on June 28, 2024. We analyze the causes, impact on infrastructure, and the urgent need for improved urban planning and drainage systems. This serves as a critical reminder of the vulnerabilities faced by our rapidly urbanizing cities in the face of extreme weather events.

Key Facts:

1. Record-Breaking Rainfall: On June 28, 2024, Delhi experienced 228.1 mm of rainfall within 24 hours, making it the highest single-day rainfall in June since 1936. This downpour was more than three times the June average of 74.1 mm and the highest for the month in at least 16 years.
2. Meteorological Conditions: According to the India Meteorological Department (IMD), the heavy rainfall was due to several meteorological factors. The monsoon circulation, previously stalled over eastern India, revived on June 25 with the development of an upper air cyclonic circulation over central and adjoining north Bay of Bengal. Concurrently, the Southwest Monsoon current over the Arabian Sea strengthened, supported by an east-west Shear Zone across northern peninsular India.
3. Infrastructure Strain: The city's drainage systems, not designed to cope with such extreme weather, were overwhelmed. Drains overflowed, leading to severe waterlogging. Visuals shared on social media showed inundated roads and long traffic snarls, indicating the city's struggle with rapid urbanization and inadequate drainage infrastructure.
4. Impervious Surfaces: The increasing conversion of pervious surfaces to impervious ones, such as concrete roads and buildings, exacerbates the flooding issue. The lack of green spaces and grasslands, which could absorb rainwater, leads to more surface runoff and water accumulation, as there is no way for the water to seep into the ground and recharge groundwater levels.
5. Cascading Problems: The flooding disrupted daily life, causing significant traffic delays and damage to property. The IMD's forecasts of continued heavy rainfall over the weekend raised concerns about further disruptions. Experts emphasized the need for comprehensive urban planning and improved drainage systems to mitigate the impact of such extreme weather events.

Detailed Analysis:

The rainfall event on June 28 was a result of a complex interplay of meteorological phenomena. The monsoon revival, influenced by the upper air cyclonic circulation and the strengthened monsoon current over the Arabian Sea, created conducive conditions for heavy rainfall. The presence of an east-west Shear Zone and the development of a low-pressure area over the northwest Bay of Bengal further intensified the situation.

The IMD's statement highlighted that the mesoscale convective activity, driven by thermodynamic instability, led to intense thunderstorms and heavy rainfall. This synoptic weather pattern was supported by strong southeasterly winds from the Bay of Bengal, which carried warm, moist air to Northwest India, including Delhi.

Infrastructure and Urban Planning:

Delhi's existing drainage infrastructure is inadequate to handle such high volumes of rainwater. The rapid urbanization and encroachment on natural drainage systems have left the city vulnerable to flooding. The drainage network covers only about 20% of the road network, far below the requirement to manage stormwater effectively.

The report emphasizes the need for green infrastructure, such as parks and open spaces, which can absorb rainwater and reduce surface runoff. The transformation of pervious areas into impervious surfaces leads to increased flooding and strain on the drainage systems. Proper urban planning, incorporating stormwater management practices like rainwater harvesting and the creation of retention basins, is crucial for mitigating the impacts of such extreme weather events.

Conclusion:

The rainfall event on June 28, 2024, serves as a stark reminder of the challenges posed by extreme weather in urban areas. Delhi's experience underscores the urgent need for robust infrastructure, better urban planning, and sustainable practices to manage stormwater and reduce the risk of flooding. As climate change continues to influence weather patterns, cities must adapt to ensure resilience against future extreme weather events.