On many occasions, a yellow-brown foam has been observed in rivers, creeks and canals in many areas across Queensland.

Scientific examination of this foam has revealed the presence of vegetable material, such as grass clippings, leaves and twigs which has presumably been blown or washed into the waterways during stormy weather. Microscopic examination has shown undifferentiated algal, vegetable and diatomaceous debris and some filamentous organisms, namely iron bacteria.

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

Bacteria examination has shown faecal coliform levels to be within the guidelines for recreational water, as described by the National Health and Medical Research Council, namely less than 200 faecal coliforms per 100mL of sample.

Chemical tests have also shown no increases in ammonia or phosphate concentrations above background levels. The low faecal coliform, ammonia and phosphate results indicate that the foam is not due to sewage contamination.

The foam appears to be formed by the action of wind and waves on the proteinaceous by-products of decaying vegetable matter, causing entrapped air to persist as a foam.