Waves of rain: on Odisha and intense rain events

During the Indian southwest monsoon, low-pressure systems and depressions typically form over the Bay of Bengal and move inland, generating widespread rainfall. While an average monsoon season typically sees around 4 to 6 such low-pressure depressions, 2026 recorded an extraordinarily high frequency of 11 systems, leaving river basins continuously overwhelmed without dry intervals to drain.

The India Meteorological Department (IMD) benchmarks monsoon performance against the Long-Period Average (LPA), calculated from 50 years of historical data (currently 868.6 mm for the 1971-2020 period). A seasonal forecast below 90% of LPA signifies a “deficient” monsoon. El Niño refers to the abnormal warming of sea surface temperatures in the equatorial central and eastern Pacific Ocean, which disrupts global atmospheric wind patterns and historically suppresses Indian monsoon rainfall.

Successive monsoon depressions in July and August 2026 triggered severe flooding across 20 out of Odisha’s 30 districts. The cumulative surge inundated vast tracts of agricultural land along major river basins, causing widespread displacement and prompting the State government to release emergency flood assistance packages.

Bhadrak and Jajpur are low-lying coastal plain districts in Odisha traversed by the Baitarani and Brahmani river networks. Whenever upstream catchment areas experience intense rainfall bursts, sudden water discharge quickly exceeds embankments in these low-gradient plains, making them chronic hotspots for severe inundation.

In hydrology, the moisture already present in the soil before a rain event is known as Antecedent Moisture Condition (AMC). When prolonged showers completely saturate the soil pores, infiltration capacity drops to zero; any additional rainfall cannot soak into the ground and immediately transforms into surface runoff, drastically shortening the time it takes for rivers and drains to flood.

Odisha exhibits stark physiographic contrasts between the Eastern Ghats highlands in the south (districts like Gajapati, Rayagada, and Koraput) and the coastal “hexadeltaic” plains formed by six major rivers (including the Mahanadi, Brahmani, and Baitarani). While steep mountain slopes trigger landslides and rapid runoff in the south, the flat coastal plains feature extremely gentle gradients (near-zero slope). This low slope drastically slows seaward discharge, trapping floodwaters for days, especially during coastal high tides.

Following the catastrophic 1999 Super Cyclone that killed nearly 10,000 people, Odisha institutionalized a globally acclaimed “Zero-Casualty” disaster management doctrine focused on early warnings and swift mass evacuations. However, in 2024, the Comptroller and Auditor General (CAG) published a performance audit on Odisha’s urban local bodies, revealing that municipal corporations lacked storm-water master plans and failed to desilt or maintain drains, leaving urban centers chronically prone to waterlogging despite flawless evacuation records.

The Baitarani, Budhabalanga, Jalaka, and Rushikulya are rain-fed river basins across northern, coastal, and southern Odisha that respond rapidly to monsoon depressions. The Jalaka and Budhabalanga rivers in Balasore and Mayurbhanj frequently breach danger levels within hours of heavy rainfall, the Baitarani inundates Bhadrak and Jajpur, while the Rushikulya basin drains through Ganjam district in southern Odisha.

A 120-year climatological analysis (1901-2020) by the Odisha University of Agriculture and Technology (OUAT) revealed a significant structural shift in the State’s monsoon behavior. While the overall number of rainy days has declined (leading to prolonged dry intervals), precipitation is increasingly compressed into short, high-volume bursts. These extreme 24-hour and 120-hour downpours drastically increase flash flood and waterlogging risks without providing steady moisture for agricultural cultivation.

Created in the aftermath of the 1999 Super Cyclone, OSDMA was India’s first dedicated state disaster management agency. Its community-driven early warning networks, network of multi-purpose cyclone shelters, and specialized Odisha Disaster Rapid Action Force (ODRAF) earned international acclaim from the United Nations for evacuating over a million people with minimal loss of life during Cyclone Phailin (2013) and Cyclone Fani (2019).

Berhampur (Brahmapur) in Ganjam district is the principal commercial nerve center of southern Odisha, situated along National Highway 16 (NH-16) and the East Coast Railway’s main Kolkata-Chennai corridor. Due to obsolete urban drainage systems and choked canals, heavy downpours cause acute waterlogging, regularly submerging rail tracks and snapping national highway freight traffic between eastern and southern India.

Over the last decade, climatological data recorded by the IMD shows that the southwest monsoon retreat has become increasingly sluggish, regularly extending deep into mid-October instead of wrapping up by mid-September. Higher sea surface temperatures in the Bay of Bengal retain atmospheric moisture longer, creating fuel for intense, late-season low-pressure depressions that clash with transitioning winter wind systems.