The phrase "major flood" refers to a very large and severe overflow of water, usually caused by heavy rain, which causes significant damage to buildings, roads, and crops, and can endanger people's lives. Full definition
About six weeks after the vacation / breakup, I had what was, I believe, the eighth major flood in my apartment. (refinery29.com)
But in recent years, the frequency of major flooding events has been on the rise — and sometimes at unexpected times of year. (scientificamerican.com)
The frequency of major flooding events, in part due to climate change but greatly due to bad river management, are increasing. (dotearth.blogs.nytimes.com)