The Molonglo Valley will be home to about 50 per cent more people than originally planned for the district, updated government forecasts show, which could force the territory to retrofit a town centre area for the first time.
Population forecasts released by the ACT Treasury last month show the government expects the Molonglo Valley to house more than 86,000 people by mid-2060.
But multiple planning strategies for the city's newest district showed the government expected between 55,000 and 60,000 people would live in the area, which includes suburbs Molonglo, Wright, Coombs, Whitlam and Denman Prospect.
A draft district planning strategy for the Molonglo Valley, released last year as part of consultation on the territory's new planning system, said the district would be home to 55,000 people at completion and reached 20 per cent of that population in 2021.
The Molonglo Valley Community Forum, which represents resident and business interests in the area, has called on the ACT government to commit to reclassifying the existing Molonglo group centre as a town centre through an overhaul of the planning system.
The forum's submission said the new population estimates showed there would be a substantial increase in the required provision of accommodation, shops, transport links and key amenities including schools and recreational facilities.
"Failure to adequately plan for these basic community needs at this early stage will have dire consequences for the future liveability of the district," the forum's submission said.
The forum wants the government to develop a precinct plan for a reclassified town centre and a review of building controls to ensure residential development does not crowd out community facilities.
The forum's convenor, Ryan Hemsley, said there was still time to make the district work for a larger population, but planning work needed to begin to ensure the area could accommodate an extra 31,000 people.
"The risk with not doing this planning now, is that we'll probably end up with 86,000 residents anyway, but we won't have the facilities and infrastructure needed to support them," Mr Hemsley said.
The district strategy, which was not updated before community consultation closed, indicated the Molonglo group centre could become "more like a town centre, servicing a wider catchment than the district itself".
A government spokeswoman said a key element of the Molonglo Valley draft district strategy was the ability of the group centre to transition to a town centre "if needed to support a larger population".
The updated population projections will not require major changes to the draft district strategies, except to bring forward the timeline for delivering new dwellings, the spokeswoman said.
"The draft district strategies, which just closed for public consultation, are designed to be evolving documents that help guide the ACT Government's response to population growth," she said.
The population projections show Canberra's northside will nearly double in population size over the next four decades to house more than half-a-million people, taking in about 65 per cent of the capital's residents.
The updated figures - which take into account the 2021 census, which revealed an undercount of residents - have already forced the government to bring forward the date by which 100,000 new homes will be required from 2063 to 2050.
The ACT's population will grow to more than 784,000 people in June 2060, at an average growth rate of 1.4 per cent a year, the government believes.
"The projected population for June 2058 is around 63,000 persons higher than the previous projections published in 2019," the government said.
The Molonglo Valley district will be Canberra's fastest growing area in the next 40 years, growing at an average annual rate of 5.3 per cent.
Infill developments in the North Canberra area will drive the second fastest growth rate, the government said in a summary of the findings last month.
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