POLICE are studying CCTV footage in a bid to catch flytippers who dumped rubbish into the River Holme at Holmfirth.
The vandals hurled barriers from a Transco gas work site on Victoria Bridge into the river.
Traffic cones from Kirklees Council highways improvements at Hollowgate in Holmfirth were also tossed into the water.
Holme Valley parish councillor Royston Rogers said the signs had been cleared from the river, but the cones were still there.
Conifer trees had also been dumped in the river at Thongsbridge.
Mr Rogers said the debris could have caused flooding in the area.
"If you get a lot of rubbish it gets washed further down until just before Honley, where it tends to get stuck. Then the river starts backing up," he said. "It is also bad for wildlife. People don't realise what they are doing when they throw rubbish in.
"We get plastic sheeting and clothes. Soap on clothes and other chemicals can kill fish, and animals can get trapped.
"I can't believe people are so mindless."
Mr Rogers is confident that police will catch the culprits.
"We want these people to know that we are on the case and that the CCTV cameras do work," he said.
The bridge incident was caught on camera because Mr Rogers had asked Kirklees Council's CCTV team to monitor the river area closely during a community clean-up.
The next clean-up will be on April 23 and 24 at various sites along the river.
Teams from the Holmfirth Co-op, the Old Bridge Hotel, Cafe 100 and individual volunteers will be tidying the river up from 8am each day.
Members of Holme Valley Mountain Rescue Team will also be helping, by abseiling down a steep hill on Station Road to clear debris from behind a high wall near Wagstaffs shoe shop.
The area cannot be reached any other way and residents are lobbying Kirklees Council to do something to prevent people tipping rubbish over the wall.
Mr Rogers said anyone who wanted to help with the clean-up should call him on 01484 689999.
All volunteers should make sure they have up-to-date tetanus immunisation.