It’s actually possible to see a crest of foam on the surface of your creek or stream. Where does it come from? Water, like other liquids, have molecules that are attracted to each other. This attraction creates surface tension on top of the water.
When leaves, twigs or other organic substances fall into water and begin decaying, they release compounds known as surfacants. This interaction breaks the surface tension, which allows air to circulate and create bubbles. These bubbles then congregate as natural foam. The foam starts out white, but will turn brown as particles of sediment get caught in there, too.
Foam may be more prevalent on a windy day, when there is even more air circulating and whipping up bubbles; fall and spring are the best times to see foam, because during these seasons the trees are shedding more material (leaves, twigs, buds) into the creeks, all of which will decompose and form surfacants!
Some creek foam is caused by man-made materials, such as soaps or detergents. If this is the case, the foam will differ in color and smell. Natural foam gives off a fishy smell, is a cloudy brown color, and will usually appear in the morning and dissipate as the day progresses. Foam from pollution, however, has a shinier texture and will smell like laundry or dish soap- think “lemon fresh” or “lavender fields.”
If you suspect your creek foam comes from a pollutant, it’s a good idea to call the Georgia Environmental Protection Division so the foam can be tested, and a possible source located.
