Residents say Hunter River rock platform flood modelling is wrong

A spokeswoman said John Holland Gamuda Joint Venture developed the model "in accordance with the project approval" and it made sure "all affected property is captured".

The spokeswoman said the modelling captured Morpeth, Phoenix Park, Largs, central Maitland, Lorn and Hinton. These are suburbs that have expressed concern about the rock platform since news broke about the flood impact in Millers Forest.

"The effects of flooding on all properties in these areas has been assessed," she said.

"There are a small number of properties in these areas that are potentially impacted and they will be engaged during the consultation process."

Swanreach Stud owner Kiri Jenkins has a property in Hinton but the project's community and stakeholder engagement lead, Monica Porte, was unable to tell her what the flood level would be on her property with the rock wall in place during a meeting there on June 13.

Her renewed calls for that information have fallen on deaf ears.

Ms Jenkins said she was told the contractor's most recent flood data was from 2016. She said the modelling needed to take the two 2022 floods into account, pointing out that they were both major floods.

"There was no actual flood modelling done for our area and the flood modelling they do have is wrong," she said.

The 180-metre rock platform wasn't part of the original plan and is touted as a safer option to help workers construct a new bridge over the river at Tarro. The initial plan was for workers to use a pontoon.

It would be built on the western side of the river, upstream from the Hexham Bridge, and then removed and relocated to the eastern side. It would be taken away once the new bridge was finished.

Ms Jenkins and Millers Forest cattle farmer Gloria Green have told the Mercury the flood modelling focused on homes that would be effected. They were both given this information during consultation meetings.

Related: Maitland councillors push for answers on rock platform

"Water flows across a floodplain. How does it go higher on one property and not the one next to it? They can't answer it. They say it's only individual properties that are effected but if you know how it floods here you'd know that just doesn't make any sense," Mrs Green said.

"I have been told that it's just the houses they're focusing on and that's not good enough.

"What about our farms - the infrastructure, the livestock, the machinery, the sheds? This is our livelihood. Our income doesn't just turn up in our bank account each week or fortnight."

Ms Jenkins said she was told the risk had been broken up into 5 tiers and there were between 140 and 150 people notified.

"The top tier was the people who never got water in their house and because of a 50 millimetre rise they were possibly going to get water on the steps or some in the house", she said.

"The next one was that they already got water but it was going to be slightly higher and tier 3 was the people who would definitely have water in the house."

Tiers 4 and 5 would be low-lying areas that would flood, she said.

"The planning for this project started in 2017 and this is probably why they've only got the flood modelling up to 2016," Ms Jenkins said.

Community consultation to continue

Transport for NSW has confirmed it has the final say on whether the rock platform will go ahead and said it was committed to consulting with communities and other stakeholders.

"Any proposed change to the original project approval required consultation with all identified affected property owners," the spokeswoman said.

"No decision has or will be made on this new proposed construction method until community consultation is completed."

The spokeswoman said the contractor had proposed the rock platform and it would reduce construction time "by several months" and narrow the potential flood risk.

"It would also allow for better environmental and safety outcomes. This proposed methodology is being considered to minimise the impact on the community," she said.