GRAND HAVEN, MI – A plume of brown water streaming out of the Grand River into blue Lake Michigan doesn't look good.
A number of MLive and Muskegon Chronicle readers expressed concern that the plume was raw sewage and harmful substances after aerial photos were published on Tuesday.
But professor Alan Steinman of Grand Valley State University's Annis Water Resources Institute says the color isn't a reason to panic."I'm pretty confident you're looking at a lot of sediment," Steinman said of a aerial photos shot by Marge Beaver of Photography Plus showing the brown water flowing out of the Grand River's mouth in Grand Haven.
The term sediment refers to a variety of particles from silt to gravel, he said all of which are being moved by a powerful flooded river currents. The sediment comes from rainwater erosion everywhere from the fields to the riverbanks themselves, which erode during a flood.
The floodwater runs higher on the riverbanks than normal and spills over them, collecting loose soil and other materials.
"Everything is being mobilized and getting into Lake Michigan," Steinman said.
That's not to say the water is clean.
The Ottawa County Health Department has an ongoing no-contact water advisory for the full length of the Grand River. The city of Grandville last week reported spilling sewage into the river on April 18, 2013.
And Steinman said that's just one source of bacteria in the water: Rain water has carried with it a variety of animal waste from fields and forests.
"It's a concern," Steinman said. "Fortunately, it's the time of year when you're not likely to have a lot of recreation activity."