A plan to raise the wall of Warragamba Dam to prevent flooding has been criticised by an expert who says it won't make western Sydney residents any safer.
The NSW government plan will see the dam wall raised by about 14 metres in an attempt to reduce and manage the flood risk to the 134,000 people who work and live in the Hawkesbury-Nepean Valley.
Australian National University Associate Professor Jamie Pittock claims the plan won't make nearby residents safer and instead pointed to alternative options.
"If the government was really concerned about flood safety - they would institute a buyback program for most flood-prone places to get people out of harm's way," Prof Pittock told AAP on Wednesday.
He said the government should also improve evacuation routes, prevent development on the most flood-prone lands and then consider lowering the dam's storage level to create airspace to temporarily store floodwaters.
Some of these options have been ruled out by the NSW government in its Hawkesbury-Nepean Valley flood risk management strategy.
The government in September introduced an amendment bill to the upper house to permit the flooding of more than 4000 hectares of national park in the Blue Mountains world heritage area to allow the wall to be raised.
The bill was referred to an upper house parliamentary inquiry for review which on Wednesday recommended it for debate.
Community group Give A Dam spokesman Harry Burkitt said it would allow the "permanent destruction" of a world heritage state.
The inquiry, led by Liberal MP Taylor Martin, in its final report said the bill intends for only a "temporary inundation" of the national park for flood mitigation purposes to improve evacuation times and save lives.
In its recommendation, the inquiry said if the bill wasn't passed this year it could cause significant delays to the project.