"Did a megaflood kill off America's first metropolis? Mississippi River and NOT droughts to blame for demise of Cahokia"

Cahokia is the large mound-builder city near present day St. Louis. According to this Daily Mail article, the culture there flourished during several centuries of dryer weather between 600 A.D. and 1200 A.D. that encouraged people to build on the flood plain. However, a series of floods beginning after 1200 apparently led to the decline and abandonment of the settlement by 1400 A.D. According to the physical data, some of these mega-floods would have been 10 meters (33 feet) above the river's normal water level.