Archaeologists excavating the Keezhadi site near the Vaigai river in Tamil Nadu found remains of an ancient settlement, including brick walls and pottery. Researchers from Ahmedabad's Physical Research Laboratory and Tamil Nadu's Department of Archaeology used optically stimulated luminescence (OSL) dating to find when flood sediments covered these structures. The team took sediment samples from two pits at different depths. They measured trapped radiation in quartz grains to estimate burial ages. Results showed the flood deposits range between 670 and 1,170 years old. The findings suggest a major flood about 1,155 years ago laid down sand, silt, and clay layers over parts of the town. This high-energy flood likely forced residents to leave or relocate. The study highlights how natural events reshape human settlements over time. It also helps distinguish between when people lived at Keezhadi and when floods buried their remains. The research offers new timelines to plan future digs and better understand the site's history. Published in Current Science on October 25, this work combines archaeology with natural science methods to read the past hidden beneath the river floodplain.