In many areas across Queensland, a yellow-brown foam can be seen in rivers, creeks and canals.

A scientific study of the foam indicates the presence of vegetable material, like grass clippings, leaves and twigs which have blown or washed into the waterways.

Microscopic observation has shown:

• algae
• vegetable debris
• traces of naturally occurring minerals
• some organisms, namely iron bacteria.

The iron bacteria are normally associated with brown material washed out of storm water systems.

Bacterial analysis has shown faecal coliform levels (faecal coliforms are a sign of human waste in the water) to be within acceptable limits, that is less than 200 faecal coliforms per 100 millilitres water sample.

Chemical tests have also shown ammonia and/or phosphate are not above background levels. The low faecal coliform, ammonia and phosphate results show that the foam is not due to sewage.

The foam appears to form by the action of wind and waves on decaying vegetable matter, causing entrapped air to create foam.