Why would there be soap suds in a stream??

Question

Why would there be soap suds in a stream??

Answer 1

Its foam, and air , and temps, movement creates it.  

Answer 2

detergents in runoff water

Answer 3

If you're seeing foam in a stream it's not necessarily soap suds. It could be a naturally occurring phenomenon.

"Foam often is seen accumulating against logs or on the banks of streams, or along the shores of lakes on windy days. When it first appears, foam can be white, but generally turns brown over time. The development of foam occurs due to changes in the water surface tension and the physical introduction of air. There is a slight tension on the surface of water caused by the chemical attraction among water molecules. This tension is what allows some insects to move along the water surface and what causes water to “bead up” on your car during a rain storm. Certain molecules interact with the water reducing the surface tension. These molecules are called surface active agents or surfactants. Foam is produced as air, introduced in the turbulence of stream riffles, below waterfalls, or as waves break upon the shore, bubbles to the water surface."

Quote above taken from paper linked to below.

Answer 4

There are two reasons:

1 - pollution from detergents or other materials entering the stream from runoff.

2 - Natural occurring materials that produce a similar effect, like saponins which are found in many plant leaves.