More than 900 people marched in Katoomba on Sunday to protest the raising of the Warragamba Dam wall by 14m.
Protesters gathered at Carrington Place where 48 nails were hammered into a coffin that was carried throughout the march, symbolising the identified species that may be pushed to extinction if the dam wall raising went ahead.
It comes as the UN's Educational, Scientific and Cultural Organisation (UNESCO) arm, released a report raising concerns about the Blue Mountains World Heritage listing if the dam wall raising occurs.
The report recommends the World Heritage Committee request the Environmental Impact Statement on the dam plan (being developed by the NSW government) be submitted to the World Heritage Centre for review before any final decisions are made on the project.
The march traversed Katoomba, Waratah and Lurline streets to gather at Kingsford Smith Park. Give A Dam campaigner and march organiser Harry Burkitt from the Colong Foundation called on the federal government to act. "The World Heritage Committee has spoken, they don't think it's a good idea - and now it's time for the federal government to step up and stop this dam project," he said.
"Raising Warragamba Dam could be the last straw that would put this iconic Australian world heritage site in danger of losing its UNESCO status."
He called on federal Environment Minister Sussan Ley to step in and protect the world heritage area, and promised a fight of Franklin Dam proportions if the dam wall was raised.
Gundungurra man David King spoke of his culture being wiped out if the dam wall raising was allowed to proceed. "The flooding of this area will destroy my creation story and we cannot let that happen," he said.
Blue Mountains mayor Mark Greenhill called for the federal government to listen to the people of the Blue Mountains.
"I call on the federal government to listen to the voices of the this community and to the echoes in time ... to understand that the world heritage listing means something and stop this insanity.
"The governments want to enable more development on the floodplain at the risk of our world heritage and that is unacceptable."
Katoomba High School captain Arliah Varnellk urged the government to consider the future. "Give your kids endless opportunities to swim in the Kedumba River and walk in the Jamison Valley," she said.
Former National Parks ranger Kim De Govrik said if the proposal went ahead popular walks such as the Katoomba to Kanangra walk wouldn't be possible because the Coxs River would be impossible to cross.
The dam wall proposal was announced by then premier Mike Baird in June 2016 as flood mitigation in the Hawkesbury-Nepean Valley.