Wednesday, March 9, 2022

Update on Synthetic turf: risk and impacts associated with floods and bushfires

Mitchelton Football club synthetic turf field damaged by flooding of Kedron Brook (Brisbane)

The Queensland and NSW Flood disasters in February and March 2022 highlighted other risks and impacts that were not included in my Literature Review on Synthetic Turf (2021).

The Guardian reported on a football club in north-west Brisbane seeing its $1.5m synthetic playing field damaged and equipment washed away as flood waters inundated the sports fields beside the creek. (Favazzo 2022)

“In one word, it’s devastating,” said Mitchelton football club technical director Joe Fenech, described the damages. 

I don't think Mr Fenech was thinking of the microplastic pollution the synthetic turf caused due to the floodwaters. Much of the field's rubber infill and any loose plastic fibres would be washed away becoming microplastics pollution, adding to this pollution in the world's oceans.

One of the Football Club shipping containers containing sports equipment was washed down Kedron Brook an estimated seven kilometres from Mitchelton to The Grange, according to a Facebook report by the Club.

My literature review focussed on all the environmental problems, but it also focussed in particular on one proposed natural grass sports field conversion to synthetic turf at Hosken Reserve in North Coburg. It looked only at siting issues within that context. But siting of synthetic turf is a general problem to consider especially with regards to flood and bushfire events.

In terms of extreme weather events, both flooding and bushfire risk should be important determinants for contributing to triple bottom line assessments for Synthetic Field siting.

Bushfire considerations

The flammability of synthetic turf was previously identified in the Literature Review:

One of the issues discovered during research was the increased flammability of a synthetic turf pitch. If synthetic turf was to go ahead Fire risk plans would need to be put into place. There is a risk of sporting fans causing fire, a risk of vandals trying to start a fire on the field. Currently the oval is occasionally used by people to set off fireworks as this is the only local space to do so for nearby residents. This would no longer be acceptable from a fire risk point of view, but I wonder if  New Years Eve revellers would accept this restriction? Accompanying the fire risk is the toxicity and health risk of smoke from any fire for local residents.(Kukfisz, B., 2018)

The report by Ethos Urban (Fokkema etal, July 2021) for the NSW Department of Planning, Industry and Environment went into more detail on fire risk, especially for bushfire prone areas.

Within bushfire-prone areas, the nature of vegetation surrounding houses and buildings has a very strong influence on the degree of bushfire damage/loss risk to which a building is exposed. It was noted in the community workshops that the presence of combustible materials or exposure to high radiant heat levels, such as those involved in the construction of synthetic fields, could increase the risk of adjacent housing or buildings to be ignited in a bushfire. As such, for regional and bushfire prone communities where the local oval is often a muster point, these bushfire considerations need to be considered if adopting a synthetic surface material.

The report also highlighted that "further research is needed into the appropriateness of synthetic turf in bushfire prone areas, where synthetic turf may contribute to bushfire risk."

Flood considerations

Siting of natural turf and synthetic turf in flood prone areas both carry environmental impacts. Many sporting fields in urban areas are sited on flood prone land beside creeks and rivers. This provides some flood mitigation given propensity for flash flooding from surrounding urban hard surfaces. 

Extreme weather torrential rain events are also increasing in both intensity and frequency due to climate change. The IPCC 6th assessment  Working Group II report highlighted in the Factsheet for Australiasia that "Heavy rainfall intensity is projected to increase." The Summary for Policymakers for this report at SPM.B.5.1 identified "heavy rainfall will increase compound flood risks (high confidence)."

The Ethos Urban report identifies that "many issues that constrain optimal utilisation of natural turf fields are intensified when they are located in poor drainage or flood prone areas, ex landfill sites, or where they have a dual purpose as stormwater retention basins. Where synthetic or natural turf fields are located in areas prone to flooding, or subject to overland flows during extreme weather, there can also be issues related to pollution of local waterways or bushland with infill materials or pesticides."

The Ethos Urban report identified that many sporting fields in NSW are constructed on flood prone land, often beside creeks in urban areas. 

"consultation undertaken to inform the Study highlighted that many existing sports fields in NSW have been delivered on flood prone land, and during extreme wet weather, can be flooded. When a synthetic turf field is flooded, microplastics and rubber crumb can leach into the surrounding area in high concentrations. The synthetic field can be rendered unusable from flood impact as well and a major refurbishment may be needed to restore infill to the field."

The report identifies Siting considerations for stormwater, looding, and overland lows which I quote in full:

Many sports fields in NSW are located on constrained sites, such as flood plains, low lying areas or near estuaries (i.e. not appropriate to be built on). As a result, they are often subject to tidal inundation or flooding during periods of heavy rainfall.

Sports fields are also frequently adjacent to large impermeable surfaces such as car parks, and therefore experience flooding from run-off. Some open space turf areas are also designed as flood detention basins, meaning they are designed to temporarily store excess stormwater so it can drain into the stormwater system or natural creek.

The location of the green open space is important to consider for both natural and synthetic turf fields. Poorly located natural turf fields may become waterlogged and unusable during wet weather, although upgrades to the field (e.g., introduction of sand slit drains, grass swales to divert upstream runoff) can reduce the impact of excess rainfall on turf performance .

While synthetic turf fields can generally be played on during wet weather, turf specialists, subject matter academics, environmental and community groups noted in the workshops the issues related to synthetic turf fields subject to overland flows or designed as flood basins.

For example, if a synthetic turf field floods, the infill on the field (e.g., rubber crumb, cork granules), which is generally lighter than water, can float and be blown around the field, which causes a maintenance issue, or results in infill materials being washed into local waterways and bushland - becoming a source of pollution for local ecosystems.

This can be somewhat mitigated by raising the field and developing a retention base under the field 63 (e.g., Gore Hill Oval, St Leonards) or delivering a “lip” around the perimeter of the field. However, it was noted by subject matter experts that data compiled from recent surveys illustrates that despite these mitigation measures, infill is still being discovered in surrounding environmental areas.


The damage to the two year old synthetic soccer pitch at Mitchelton football club is heartbreaking, but the flood risk for siting of this synthetic field should have been identified before hand. 

According to the Brisbane City Council Kedron Brook flood map study from 2014, "Teralba Park sporting fields are all impacted by the 1% AEP flood".  So the Michelton Football Club sporting fields are all in the 1 in 100 year flood zone.

Don't be fooled that these floods happen once every 100 years, the risk of floods is 1% in any year. But flood events of this size can happen in succeeding years. Climate change is also weighting the dice with more intense extreme weather flood events, so what was once a fairly rare flooding event now is much more likely to happen. 

This incident has destroyed expensive sporting infrastructure, caused infill to and microplastics pollution of floodwaters which ends up adding to plastics pollution in the ocean. The plastic matting will go to landfill where it will slowly break down into microplastics all the time emitting methane and ethylene gases, both high impact greenhouse gases much stronger than carbon dioxide.

Natural turf sporting fields will not cause the same polluting effect when flooded, will be easier to clean up afterwards, and will recover from flooding. Natural turf fields are far more resilient. They may cause pollution if pesticides and fertilisers are used on them immediately before the torrential rain/ flooding event. 

The use of Synthetic turf for Sporting fields in buhfire prone areas either in metropolitan or country towns is also contra-indicated. 

These sports fields are often emergency muster points during bushfires. Having crowds congreagate on a flammable surface during a bushfire would seem to escalate the health and fire risks.

There should be oversight put in place of any government grants for synthetic turf to ensure siting and environmental impacts are fully taken into account as part of a triple bottom line assessment of environmental, social and economic benefits and impacts of installing synthetic turf rather than natural turf sporting fields.

This is an opportunity for the Mitchelton Football club to revert the synthetic field sports field to natural turf. They should be supported in this, and in replacing the flood damaged sports club buildings, sheds and equipment, by local and state government as part of flood damage assistance, and building community resilience.

Mitchelton Football Club president Gary Green estimated the restitution and repair of the synthetic pitch may be $500,000, according to this ABC report. Is repairing the synthetic field really an economic proposition given the field is in the floodzone and just as likely to be damaged in an extreme rain and flood event next year, or the year after?


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