Somebody allowed chemicals into the stormwater and here it has created visible suds.
This stormwater drain discharges directly into the river. Many of the street drains have a little fish symbol on them to remind people that the drain goes directly into natural water courses. We’re meant to be careful about washing chemicals to avoid poisoning the wildlife and their habitats. There’s a lot of invertebrates that are quite sensitive to such pollution. We’re advised to wash cars over grass so the wash chemicals will soak into the earth and be broken down before reaching a waterway.
However, this looks industrial. I posted this drone pic on our local Facebook page and other residents added more information. The local council is now investigating.
Oh, and the water level is very low: That sand bar to the left is usually not visible. Most likely the river authority is expecting more rain.