Human-driven sea level rise has increased how often extreme coastal flooding occurs around the world, according to a study released Wednesday. Experts say the findings are crucial for coastal infrastructure and flood planning as the planet warms. Extreme flooding events are caused by a combination of storm surges, high tides and unusual sea level rise. Historically rare extreme sea level events — those that happen once per century — are now, on average, about 12 times more likely, according to the study, published in the journal Nature Climate Change.