The District’s climate and natural landscape can create natural hazards such as heatwaves, bushfire, flooding and storms. Climate change will exacerbate these natural hazards, leading to higher temperatures and changes in rainfall, with consequent flooding. While planning for resilience has traditionally focused on responses to natural hazards and climate change, it is increasingly being used to consider a wider range of social and economic shocks and stresses.
Effective planning can reduce the exposure to natural and urban hazards and build resilience to shocks and stresses. Planning for population growth and change needs to consider exposure at a local level as well as cumulative impacts at district and regional levels.
State agencies and councils use a range of policies and tools to reduce risks from natural and urban hazards. Centralised and coordinated collection of data on hazards, particularly on how infrastructure is exposed to hazards, will help embed resilience in land use planning and infrastructure planning.
Natural and urban hazards
The climate, vegetation, topography and pattern of development in the District mean that bushfire and flooding will continue to be a hazard. Placing developments in hazardous areas or increasing the density of development in areas with limited evacuation options increases risk to people
Climate change is likely to result in a longer bushfire season with more bushfires, and longer lasting heatwaves with more extremely hot days. Areas such as Penrith experience on average 21 very hot days (above 35 degrees), with projections for an additional five to 10 very hot days per year in the near future. Heatwaves kill more people than bushfires, with disadvantaged and elderly people most affected.
Past and present urban development and activities can also create urban hazards such as noise, air pollution and soil contamination. Compared to many cities around the world, Greater Sydney enjoys excellent air quality, which enhances its reputation as a sustainable and liveable city. However, the combined effect of air circulation patterns in the Sydney Basin, local topography, and proximity to different sources of air pollution such as wood-fire smoke, can lead to localised air quality issues.
Transport movements along major roads and rail corridors generate noise and are a source of air pollution. The degree of noise or air pollution can be related to the volume of traffic and the level of truck and bus movements. The design of new buildings and public open space can help reduce exposure to noise and air pollution along busy road and rail corridors. Public transport, walking and cycling, as well as hybrid and electric cars, provide opportunities to reduce air pollution. The NSW Government has recently strengthened regulation of ventilation outlets in motorway tunnels, which will also help reduce air pollution.
Soil and groundwater contamination is another urban hazard which will require careful management as the District grows, and land uses change. This is particularly important when planning for more sensitive land uses such as schools, open space and low-density residential neighbourhoods, in areas with the potential for pre-existing contamination. State Environmental Planning Policy No. 55 – Remediation of Land and its associated guidelines manage the rezoning and development of contaminated land.
Greater Sydney, particularly its rural land, is at risk from biosecurity hazards such as pests and diseases that could threaten agriculture, the environment and community safety. Biodiversity hazards are managed by the NSW Government through the Greater Sydney Peri Urban Biosecurity Program.
Consideration of natural hazards and their cumulative impacts includes avoiding growth and development in areas exposed to natural hazards and limiting growth in existing communities that are exposed and vulnerable to natural hazards. In exceptional circumstances, there may be a need to reduce the number of people and amount of property that are vulnerable to natural hazards, through managed retreat of development.
The impact of extreme heat on communities and infrastructure networks can also be significant. More highly developed parts of the District can be exposed to extreme heat as a result of the urban heat island effect. Increasing tree canopy cover is important to help reduce those impacts. The State Heatwave Sub Plan, which the NSW State Emergency Management Plan, details the control and coordination arrangements across State and local governments for the preparation for, response to, and immediate recovery from a heatwave.
Current guidelines and planning controls also focus on minimising hazards and pollution by:
- using buffers to limit exposure to hazardous and offensive industries, noise and odour
- designing neighbourhoods and buildings that minimise exposure to noise and air pollution in the vicinity of busy rail lines and roads, including freight networks
- cooling the landscape by retaining water and protecting, enhancing and extending the urban tree canopy to mitigate the urban heat island effect.
Minimising interfaces with hazardous areas can reduce risks. Clearing vegetation around developments on bushfire-prone land can help reduce risks from bushfire, but must be balanced with protecting bushland, and its ecological processes and systems. Planning on bushfire-prone land should consider risks and include hazard protection measures within the developable area. The Rural Fire Service requires new developments to comply with the provisions of Planning for Bush Fire Protection 2006.
Managing flooding is an important priority for communities across the Western City District. The NSW Government has developed the Floodplain Development Manual 2005 to guide development on areas at risk of flooding. Councils are responsible for managing flood risk in their local government areas and typically impose flood related development controls in areas below the 1 in 100 chance per year flood level.
In the case of the Hawkesbury-Nepean Valley, the significant depths between the one in 100 chance per year flood and the probable maximum flood, mean a risk-based approach that considers the full range of flood sizes is more appropriate. Refer to following summary – Flooding in the Hawkesbury-Nepean Valley.
Flooding in the Hawkesbury-Nepean Valley
The size and topography of the Hawkesbury-Nepean Valley means it has the greatest flood exposure in NSW. Unlike most other river catchments in Australia, the Hawkesbury-Nepean Valley floodplain has significantly higher depths during flood events created by several narrow gorges in the Valley that constrict the flow of floodwater downstream. There is a complex interaction between the main flow of the river and the multiple rivers and creeks that contribute to the catchment, creating what is known as a ‘bathtub effect’. Evacuation of people in extreme events is made complicated by the size of the area affected and the need to evacuate certain areas early before they become isolated by rising flood waters.
Some communities are built on ‘flood islands’ that can also become isolated during floods, and key evacuation routes can face congestion or inundation during higher floods. This may be further exacerbated through incremental or large scale development in effected areas, especially in Richmond, Windsor and Bligh Park. This creates challenges for urban development and emergency management planning in the catchment.
Resilient Valley, Resilient Communities – Hawkesbury-Nepean Valley Flood Risk Management Strategy 2017 aims to reduce the potential risk to life, the economy and communities. This strategy highlights the importance of strategic and integrated land use and road planning and adequate local roads for evacuation.
Given the scale of the severity and regional-scale of the risk, more stringent consideration is warranted for areas affected by the probable maximum flood (PMF) as well as the 1:100 year flood. The NSW Department of Planning and Environment is leading work to develop a planning framework to address flood risk in the Hawkesbury-Nepean Valley. This will include an examination of the cumulative impact of development within the Hawkesbury-Nepean Valley on flood risk. While this work is underway, the following planning principles will be applied to both local strategic planning and development decisions:
- avoiding intensification and new urban development on land below the current 1 in 100 chance per year flood event (1 per cent annual exceedance probability flood event)
- applying flood related development controls on land between the 1 in 100 chance per year flood level and the PMF level
- providing for less intensive development or avoiding certain urban uses in areas of higher risk and allowing more intensive development in areas of lower flood risk, subject to an assessment of the cumulative impact of urban growth on regional evacuation road capacity and operational complexity of emergency management
- balancing desired development outcomes in strategic centres with appropriate flood risk management outcomes
- avoiding alterations to flood storage capacity of the floodplain and flood behaviour through filling and excavation (‘cut and fill’) or other earthworks
- applying more flood-compatible building techniques and subdivision design for greater resilience to flooding.
Penrith Lakes is a former quarry site being rehabilitated into lakes, wetlands and parklands, located mostly within the Metropolitan Rural Area. As Penrith Lakes is in the Hawkesbury-Nepean Valley floodplain, planning for any future development will need to carefully consider the significant risk to people and property from flooding during extreme events. Investigations undertaken by the Hawkesbury-Nepean Flood Risk Management Taskforce identified that there is no ability for major residential development to occur at Penrith Lakes This is due to the characteristics of the site as well as the limited ability of existing or future infrastructure to create the necessary road evacuation capacity to service the new developments and maintain evacuation routes for places such as Richmond and Londonderry.
Some alternate forms of development may be considered, if they avoid increasing risks to people and property, including evacuation impacts. The amendment to State Environmental Planning Policy (Penrith Lakes Scheme) 1989 allows certain urban uses such as tourism, employment and limited residential development in areas subject to operational plans that build flood resilience and avoid the creation of communities that require evacuation.
Flooding constraints also affect other areas across the District, many of which are undergoing significant growth and redevelopment. This includes the Penrith City Centre, where drainage works are underway to manage flooding. Strategic planning for growth in flood-prone areas must consider flood resilience to ensure buildings and communities can withstand flood events and quickly recover.