Urban Development, Greenhouses Gases can Trigger Extreme Floods When the rain started to pour down in northern Georgia on September 15 th, 2009, the residents of Atlanta were completely unaware that they would be witnessing epic flooding across the city. Image Credit: Discovod/shutterstock.com Localities, including Peachtree Hills, were inundated; the busiest expressway in Georgia was submerged, and so were the bridges and roads; the untreated sewage combined with the growing floodwaters; and people and cars were swept away. Sonny Perdue, who was the presiding governor of Georgia at that time, had announced a state of emergency. Moisture from the Gulf of Mexico drove the 2009 flood. Now, after 10 years, scientists from Arizona State University (ASU) are asking whether a mix of climate change driven by greenhouse gases and urban development could lead to similar situations in U.S. cities. And based on a recently published analysis, the answer is yes.