Ahmedabad: An analysis of heavy rainfall in the last week of August, which threw normal life out of gear and forced evacuation of nearly 30,000 people simultaneously in multiple regions, has suggested the need for "robust and scalable emergency response strategies that can handle the complexities of concurrent extreme events."
The Machine Intelligence and Resilience Laboratory (MIR Lab) at the Indian Institute of Technology Gandhinagar has done an analysis of rainfalls recorded from August 20 to August 29. The analysis of maximum rainfall during this period revealed twelve of Gujarat's 33 districts experienced one-day rainfall that exceeded the 10-year return period—a statistical measure indicating the average interval between such intense events.
The data found that Morbi and Dwarka recorded rainfall levels that surpassed their 50-year (with exceedance of 100-year for Dwarka) return thresholds, marking an intensity of rainfall that typically occurs only once in half a century. 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.
Additionally, according to the analysis, 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 that exceeded their expected return levels, emphasizing the prolonged and intense nature of the event.
"This situation is a classic example of concurrent extreme events, where multiple regions experience severe weather simultaneously. 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," the analysis has found.
"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," said Udit Bhatia, Assistant Professor in Civil Engineering and Computer Science and Engineering at the institute and Principal Investigator of the MIR Lab, who works on the resilience of urban systems to extreme events.
Bhatia further added that "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."
Bhatia gives the example of Vadodara, which has 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. However, the flooding was likely exacerbated by extensive urban development in flood-prone areas, altered elevations, and drainage patterns compromised due to rapid urbanization and clogged drainage systems," the release stated.
It further adds, "The recurrence of these unusual weather events along the western coast of India highlights the urgent need to reassess urban planning and infrastructure resilience. 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. Addressing these challenges is essential to mitigating the risks associated with increasingly frequent and severe weather events, ensuring that cities are better equipped to handle the impacts of future storms."
Gujarat received heavy rainfalls largely due to 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. The institute in a release stated that it is premature to attribute the heavy rainfall directly to climate change without proper investigation.