Questions about the effectiveness of new sediment traps designed to protect Lake Horowhenua have surfaced online, however the regional council says they are working as they are supposed to.
The traps have been constructed at the Arawhata Stream, and are designed to stop sediment washing into the badly polluted and controversial lake.
A drone video circulating on social media shows large amounts of brown-coloured water washing straight through the traps and into the lake after a heavy rainfall event, but Horizons Regional Council freshwater and partnerships manager Logan Brown said the trap was operating as it was designed.
He said he had seen the footage.
"The fact that the image starts with muddy water being in the trap shows that the flood event was large enough to start spilling some of the water into the trap but the flood wasn't large enough to divert water around the entire trap," he said.