The electronic music festival has been running at Riverwood Downs for 10 years, attracting an increasing number of patrons.

On Friday, November 29, festival organisers announced this year's event would be postponed until the new year and would take place at a new venue.

"The postponement comes amid safety concerns arising from ongoing fires in the area and critically low water levels in the Karuah River," wrote festival director Scott Commens on a Facebook post.

"This has resulted in Riverwood Downs removing permission to use the venue on the scheduled date.

"The Festival has secured a stunning new venue and a revised date and location for this summer's epic Subsonic Music Festival will be announced shortly."

The decision comes days after MidCoast Council rejected a request to extend and expand the annual festival.

At the end of July, festival organisers sought to have the festival approved for five years with an incremental increase of patron numbers permitted from 5000 to 10,000, plus an increase in volunteer numbers to include staff, artists and their guests up to a total of 3000.

This sparked concern from some of the site's closest neighbours. The Chronicle reported last month a group of residents had started a petition opposing the increase in numbers and had sought a meting with MidCoast Council.

The residents raised issues of traffic snarls on the gravel road they deemed inadequate for such large volumes of traffic and pollution in the Karuah River which was many residents' household water supply.

The former Great Lakes Council first approved the festival on November 5, 2009.

The original application for the Subsonic festival was for three days with a limit of 1500 patrons and 300 volunteers.

Each year from 2010 until 2012, organisers sought approval for the same number of people, then in 2013 it was granted an increase to 2500 patrons.

In 2014, the application asked for a five-year approval for 8000 patrons.

After council considered the history of the event and the lack of community complaints, it granted consent for the five year period but with only an increase in the numbers to 5000 people.

The approval included a reviewable condition should complaints be received.

In October 2015, council received a complaint alleging drug use, noise, environmental impact and road safety, to which council responded by issuing an official caution to festival organisers.

According to the report, the information provided to council indicates the actual total number of people attending in recent years has been approximately 7000.

The report stated that insufficient information had been submitted to support the increase in numbers and the continuation beyond 2019.

Prior to the meeting held in Forster on Wednesday, November 27, the development application (DA) had been sent to Riverwood Downs neighbours.

Council received 18 submissions of which 11 were objecting the DA. Neighbours' reasons for objecting included traffic, noise, environmental impact, drug-use and lack of water as areas of concerns.

Those who submitted in favour were employees of the festival, including the accounts manager and Riverwood Downs, listing the economic benefit to the region.

The report concluded that sufficient information had not been submitted to support the increase in patron numbers and continuation of the event beyond 2019.

It was recommend to approve the DA for one year only with a long list of conditions.

Subsonic festival organisers said all tickets remain valid for the new date and venue.

"We would like to offer our sincere apologies to all our patrons, artists, stallholders, staff and volunteers that are affected by the postponement," said festival director Scott Commens.

"Despite our best efforts to work through the concerns of the event stakeholders, unfortunately, we have been given no other option but to temporarily postpone the festival.

"We were only advised of the unavailability of Riverwood Downs at very late notice and were unable to safely change the venue for next weekend. The collaboration between Subsonic and Riverwood Downs has been a great one, spanning many years."

He said ticket holders will also gain access to a series of club shows in Sydney across the weekend of December 6-8.