As it does, the SES is reminding residents just how devastating floods can be.

In a SES produced video explaining why the region is subject to flooding, it states that flow from five main tributaries, including Warragamba, Nepean and Grose rivers, converge and reach natural choke points which restrict the speed at which the water can escape to the ocean. The SES calls this the "bathtub effect".

The unique landscape of the Hawkesbury area does not allow for flood water to escape quickly through Sackville Gorge and this leads to even minor floods having devastating effects on the community.

SES Hawkebsury Unit recommends that residents of the Richmond and Windsor floodplain find out their flood risk and how to prepare for future floods at www.myfloodrisk.nsw.gov.au.

Warragamba Dam sits at 97.5 per cent of capacity as of Thursday, November 5.

Warragamba is the primary supply for the greater Sydney region and not a flood mitigation dam. Its primarily objective is to capture and store the maximum volume of water.

Water is only released once it has reached capacity. Water is not released in reaction to a forecast rain event.

Raising the dam wall

In recent years there has been a push to raise the height of the Warragamba Dam wall as a possible solution to future flooding of the Hawkesbury Nepean valley.

The strength of the proposal recently took a blow when Insurance Australia Group (IAG) announced it had withdrawn its support.

In her address to the IAG 2020 AGM on Friday, October 23, IAG Chairman Elizabeth Bryan said: "In the past we have expressed support for the raising of the wall, however we now have additional information concerning the probable loss of significant cultural heritage sites, and important natural habitats".

Macquarie MP Susan Templeman said that the raising of the dam wall was a quick fix for flooding presented by the NSW Government.

"But it appears to be more about pleasing developers than to genuinely protect existing residents," she said.

"I welcome this IAG announcement as a sign that the plan is now receiving proper scrutiny by people who had previously advocated for it.

"From the start I have questioned why the NSW Government has refused to acknowledge that not only are there serious questions about whether the wall raising provides any real protections from flooding ... but that it does significant damage to Indigenous and natural heritage in the Greater Blue Mountains World Heritage Area."

Hawkesbury Councillor Nathan Zamprogno said IAG was aware that the estimates of property damage in the event of a bad flood ran to "tens of billions of dollars".

"Landowners experiencing huge premium hikes for flood insurance caused by the recognition of increased risk should be angry that any insurer would oppose a measure that would make them safer and lower their premiums," he said.

"How much Aboriginal heritage or environmental damage would be lost downstream of the dam if a flood like 1867 came again? No one talks about that.

"The missing voice from this debate are the 134,000 people who live and trade on the Hawkesbury Nepean floodplain - they are the people whose lives, livelihoods, and properties are at risk.

"I suspect that the morally righteous who wag their fingers and who oppose this project aren't in any personal danger like floodplain residents are. Those opponents have no personal stake in the outcome - but we do."

Cr Zamprogno also responded to Ms Templeman's comments.

"The 'Resilient Valley, Resilient Communities' plan was released in 2017 and made it clear that flood height building controls would remain unchanged," he said.

"Meaning no new development on the floodplain in any area that is currently forbidden by the 1:100 limit.

"Simon Draper, CEO of Infrastructure NSW declared there would be no changes to flood height building limits. Andrew George, the CEO of WaterNSW declared the raised dam would not be used to store more water for Sydney's drinking needs."

Mr Zamprogno said that Ms Templeman should be defending the families in the Hawkesbury that "bear the greatest risk" of loss of life and property caused by floods.

"Instead, she is captive to environmentalists whose criticism for flood mitigation comes from places of personal safety - high and dry and out of harms way," he said.

"It is clear that Ms Templeman is playing to her political base in the Blue Mountains and has effectively abandoned the Hawkesbury community to the risk of floods."