A cleanup of Flat Creek, a 6-mile waterway that cuts through Gainesville and unincorporated Hall County, eventually discharging into Lake Lanier, is expected to draw 100 or more people Saturday morning.Even though groups have preregistered for the Gainesville-Hall County Rivers Alive Stream Cleanup, showing up unannounced is fine.“Be prepared to get dirty and get wet,” said Brian Wiley, Gainesville’s environmental monitoring coordinator. “Wear a life jacket, if you have one, because the water is deep in (certain) areas.”Flat Creek’s stormwater troubles are well-documented, including being listed on the state Environmental Protection Division’s Impaired Water List.But even longtime residents were shocked by what they saw after 4 inches of rain fell in a 90-minute episode on Aug. 10.Trash that ended up in Flat Creek “was the culmination of a lot of debris, a lot of stuff on the ground, stuff that was already in the creek from downtown,” said Horace Gee Jr., Gainesville’s environmental services administrator, at the time. “It was such a heavy rain that it basically ... cleaned Flat Creek out from downtown Gainesville to Lake Lanier.”Wiley said the annual cleanup usually serves as reminder to people “that when you throw something out on the ground, it goes to a storm drain, which goes to a stream — not a treatment plant.“The idea is ... to get everybody on the same thought process of what they can do to continue to improve the habitat, the water quality and the environment,” he added.Flat Creek is looking better these days, Wiley said.“Since (August), a lot of the natural debris has decomposed, so it’s starting to settle out a little bit and starting to dissolve,” he said.