‘Intense rainfall in Gujarat worsened by extensive urban development in flood-prone areas’: IITGN study

These are some of the key insights of an analysis of maximum rainfall between August 20 and August 29 conducted by researchers at the Machine Intelligence and Resilience Laboratory (MIR Lab) at the Indian Institute of Technology, Gandhinagar.

Terming the spells of rain across Gujarat as a classic example of concurrent extreme events, where multiple regions experience severe weather simultaneously, the researchers said that such concurrence complicates emergency response and evacuation efforts as resources become stretched across multiple affected areas.

The overlapping demands for rescue, relief, and evacuation operations can overwhelm emergency services, making it more challenging to respond effectively and efficiently to the needs of those impacted by the floods. This underscores the need for robust and scalable emergency response strategies that can handle the complexities of concurrent extreme events.

For example, in Vadodara, which experienced severe urban flooding during this period, the three-day rainfall corresponded to a return period of less than 10 years. This suggests that the heavy rain was not unprecedented in magnitude, the researchers said.

The analysis further revealed that twelve of Gujarat’s 33 districts experienced one-day rainfall totals of such intensity that they exceeded the 10-year return period, which is a statistical measure indicating the average interval between such intense events.

“The situation became even more critical over two-day periods, with 17 districts exceeding the 10-year return period, including Jamnagar, Morbi, and Devbhumi Dwarka, where rainfall surpassed 50-year return levels,” the analysis states.

The overlapping demands for rescue, relief, and evacuation operations can overwhelm emergency services, making it more challenging to respond effectively and efficiently to the needs of those impacted by the floods. (Express photo)

Additionally, fifteen districts recorded three-day rainfall totals exceeding the 10-year return period, with Jamnagar, Morbi, Devbhumi Dwarka, and Rajkot all experiencing levels above their 50-year thresholds.

In particular, Jamnagar and Dwarka saw three-day rainfall totals that even exceeded their expected return levels, which the researchers said emphasised the prolonged and intense nature of the rain.

While these figures are striking, they should be interpreted with caution, according to the researchers.

“The granularity of the available data may not fully capture the nuances of urban flooding, which often results from short-duration, high-intensity rainfalls that overwhelm city drainage systems,” explained Bhatia. He further said, “When rainfall persists for longer durations, the soil becomes saturated during the initial spells, and subsequent rainfall is more likely to contribute directly to surface runoff. This runoff exacerbates flooding, especially when drainage systems are either incapacitated or unhealthy.”

Therefore, the recurrence of these unusual weather events along the western coast of India highlights the “urgent need to reassess urban planning and infrastructure resilience”, in Bhatia’s words. “As rapid urbanization continues to modify regional and local hydrology, placing greater strain on drainage systems, it is crucial to keep hydrology at the core of urban development strategies,” he said.

Between August 20 and August 29, Gujarat was inundated by heavy rainfall resulting from Cyclone Asna, the latest in a series of unusual weather events along India’s western coast. Following Cyclone Biparjoy in 2023, Asna has drawn attention to the growing frequency of severe weather in the region. However, experts caution that it is premature to directly attribute these events to climate change without a thorough statistical and dynamic investigation.