Emily Garner, PhD student at Virginia Tech, collects samples in the Cache La Poudre river after the Colorado floods of 2013. 

(Courtesy Emily Garner) 

When Colorado's Front Range flooded four years ago this month, huge amounts of water and sediment moved across the state. The water was actually more like a soup of everything it touched: chemicals from garages, oily runoff from roads, and waste from water treatment plants and agricultural operations.

Waste like that can include antibiotics, because when humans and animals consume the medicine much of it passes through the system unprocessed. Emily Garner, a PhD student at Virginia Tech studied the floods and told Colorado Matters host Nathan Heffel that floods diluted the presence of antibiotic-resistant bacteria -- but only temporarily. Studies have now shifted to Texas and Florida, where flooding took place after hurricanes Harvey and Irma.