Yass Valley

The LGA is vulnerable to a wide range of natural hazards, making it essential to understand the nature and extent of exposure to people, buildings, infrastructure, services, or natural resources to effectively assess and address associated risks.

Exposure can be seen in various forms:

• Relative exposure is a function of hazard, describing the frequency and magnitude of natural hazard events and capturing the compounding effect of multiple hazards (fire and flood for this analysis). Where a community is subject to both fire and flood, it is potentially less resilient than one exposed to a single hazard of the same frequency and magnitude;
• The physical exposure of a community is determined such that the quantum of exposed people, buildings, essential facilities, industry, and agriculture can be evaluated. The physical vulnerability of exposed elements is also important, such as the age and construction type of buildings (for example, buildings with raised floors are more resilient to flood as they provide greater protection to the occupants and their belongings, resulting in less loss of life and property); and
• Social vulnerability is determined by examining socio-economic and demographic factors that may exacerbate or ameliorate the effects of an external threat to a person’s life, livelihood, or assets. Examples of these types of indicators include age, occupation, health status, income and education.

The Resilience Blueprint identified the following hazards as relevant hazardous events for the southeast NSW region. In 2024 the State Disaster Mitigation Plan (SDMP) was implemented and any additional hazards or information regarding exposure of hazard in the region has been included below:

  Fire (bushfire and grass)

• Based on information collated from Risk Frontiers, the frequency of dangerous bushfire weather days and the magnitude of bushfire weather extremes will increase in Yass Valley. Earlier onsets of the bushfire season are also predicted;
• The Southern Tablelands Region (which includes the Upper Lachlan, Yass Valley & Goulburn Mulwaree LGAs) has on average 265 bush fires per year, of which 5 could be considered to be large fires. It is noted that rainfall is both unreliable in the region, and generally at its lowest during the summer months. This is known to result in dry pastures over a large proportion of the shire, increasing grassfire risk; ²⁴
• A large proportion of Yass Valley is rural in nature which influences the level of bushfire risk. Any increase in bushfires will likely have flow on effects to water quality and availability for the Yass Valley; ²⁵
• Based on the potential event probability, as provided by Risk Frontiers, annual average loss of residential, commercial and industrial buildings from flood in the LGA is 6 per cent under a RCP 4.5 scenario. This accounts for a low probability of occurring but a high financial cost consequence of bushfire activity;
• As a result of the 2019-20 bushfires in NSW, an estimated 1,331 tonnes of grapes significantly impacted by smoke taint across the Yass Valley region, with substantial implications for the viticulture; ²⁶
• There are large pine plantations 3460 hectares of both state and private in the Yass Valley Shire, valued in excess of $15 million. Pine plantations are very susceptible to fire and because of their value prevention of fire is a high priority; and ²⁷
• Historically, Yass Valley Council has been subject to significant bushfire events, including the Cobbler Road grassfire which occurred overnight on 8-9 January 2013. This started under extreme conditions and covered 14,000 hectares within 6 hours. ²⁸

Actions proposed or taken:

• Council’s LSPS identifies priorities, and subsequent actions related to bushfire:
  • Planning Priority 2: Focus Growth in Yass and Murrumbateman. Action: ‘Ensure Planning Proposals avoid areas affected by flooding and high bushfire risk and avoid agricultural land use conflict’; and
  • Planning Priority 7: Increase Yass Valley’s Resilience to Climate and Natural Hazards. Action: ‘Ensure current environmental constraints information is made available to inform Planning Proposals and Development Applications including flood planning levels, potentially contaminated land and bushfire risk’.
• The Southern Tablelands Bush Fire Management Committee updating the Bush Fire Risk Management Plan for Southern Tablelands. It identifies the bush fire risks in Upper Lachlan, Yass Valley & Goulburn Mulwaree LGAs and sets out the types of work scheduled to deal with the risk of bush fires.

 Flooding (flash and riverine)

• Flooding is a serious risk in Yass Valley. It is estimated that 10.9% of the population, or 1,900 people in Yass Valley are at risk of flooding; ²⁹
• Floods in Yass Valley are causes by either of 3 weather systems, being: ³⁰
  • Sequences of southern air masses (frontal systems) coming from the Antarctic region and moving in north easterly direction over the catchment;
  • Low-pressure systems located over the east coast of Australia (East Coast Lows) and causing moist airflows over the Snowy Mountains;
  • Short duration, high intensity convective thunderstorms that occur over small areas during summer. These may cause town drainage systems to surcharge and minor creeks to rise rapidly. Such thunderstorms do not cause mainstream riverine flooding.
• Based on the potential event probability, as provided by Risk Frontiers, annual average loss of residential, commercial and industrial buildings from flood in the LGA is 66 per cent under a RCP 4.5 scenario. This accounts for a high probability occurring and a high financial cost consequence of flood activity;
• Much of the Yass CBD (including commercial and residential properties along Yass Valley Way) is mapped as being at risk of flooding in a 1% AEP flood event;
• Yass and the villages have varying degrees of flood risk due to their historical siting adjacent to waterways. Any net increase in flooding will have flow on effects to water quality and availability for the Yass Valley; ³¹
• A number of storage dams are located in Yass Valley including Yass Dam and the Burrinjuck Dam. The Yass Dam is found to have negligible flood mitigation affect on peak flow in the Yass River. The Burrinjuck Dam contains high water storage levels within the dam, which may result in the flooding of several caravan parks and camping grounds located on the foreshores of the dam; ³²
• Whilst not formerly recorded, the largest flood in Yass was reportedly the 1900 flood; ³³
• There have been a number of significant flooding events within the Yass Valley LGA, since records began in 1915, including in October 1959, where Yass had its largest flood (on record). The Yass River peaked at approximately 9.8 metres at the Yass Gauge. Floodwaters reached the steps of the Court House and affected business premises and residents in Rossi and Comur Streets. The northern approaches to Hume Bridge were cut for approximately 12 hours. Floods have also been recorded at the Yass Guage for the following dates and heights: ³⁴
  • Friday 31 October 1969 (5.90m);
  • Wednesday 28 August 1974 (7.63m);
  • Thursday 5 September 1974 (5.33m);
  • Friday 18 October 1974 (5.06m);
  • Monday 14 July 1975 (4.23m);
  • Saturday 25 October 1975 (4.18m);
  • Saturday 17 October 1976 (4.86m);³⁵
  • Tuesday 5 September 1978 (4.44m);
  • Saturday 21 September 1985 (4.05m);
  • Wednesday 15 March 1989 (6.84m); and
  • Thursday 13 April 1989 (4.33m).
• In 2020, major flooding impacted Yass, resulted in more than $427,000 in flood damage to infrastructure (when calculated by Council); and
• More recently, in August 2022, flooding from the Yass River caused significant damage (greater than $2.5 million). For the 2020 flood, the peak flow rate was 80,000 megalitres a day; the August 2022 flood had a peak flow rate of 125,000 megalitres a day. Flooding was caused by storm activity and resulted in flooding from overland flow and riverine flooding in Yass. ³⁶

Actions taken or proposed:

• Council’s LSPS identifies the following actions relevant to addressing flood risk as priorities:
  • Complete Flood Studies for Murrumbateman, Bowning, Binalong and Bookham (short-term);
  • Complete Yass Flood Risk Management Study and Plan (short-term);
  • Commence Parkwood Flood Risk Management Study and Plan (medium-term); and
  • Implement development recommendations of Flood Risk Management Studies and Plans into Comprehensive Development Control Plan (short-medium term).
• Council have also completed several flood studies and floodplain risk management plans to better understand flood risk within the LGA, including: ³⁷
  • Murrumbateman, Bowning, Bookham and Binalong Flood Study 2020 (and the July 2021 update), prepared by Lyall & Associates Pty Ltd;
  • Sutton Floodplain Risk Management Plans 2016, prepared by WMA Water; and
  • Yass Floodplain Risk Management Report 2021, prepared by Lyall & Associates Pty Ltd and Nexus Environmental Planning Pty Ltd.

These strategies also provide and recommend various flood risk measures for these areas to ensure any new development can be aware of any present flood risk.

 Severe storm

• Severe storms in NSW are often associated with East Coast Lows (ECL). ECL events are extreme weather systems that occur in South-East Australia, bringing extreme winds, rain, hail and lightening;
• The maximum annual windspeed is projected to increase across the LGA; and
• Based on the potential event probability, as provided by Risk Frontiers, annual average loss of residential, commercial and industrial buildings from hail damage associated with a storm in the LGA is 17 per cent under a RCP 4.5 scenario. This accounts for a low probability of occurring but a high financial cost consequence of severe storm activity;

Note: for the purposes of this report, cyclone was not commented on.

Actions taken or proposed:

• No actions have been taken or proposed for to address storm and cyclone risks within the LGA.

 Landslide

• Landslide can be triggered by severe weather events (e.g. heavy rainfall) or human activities (vegetation removal, overgrazing, slope modification, etc.).³⁸
• The probability of landslides in the region are considered rare, but the level of consequence can be high depending on the location. This risk is higher in parts of the LGA with steep topography.

Actions taken or proposed:

• No actions have been taken or proposed for to address landslide risks within the LGA.

 Heatwave

• A heatwave is generally defined as ‘a period of abnormally hot weather lasting over several days’, and can be characterised as three or more days of high maximum and high minimum temperatures that are unusual for that location;’ ³⁹
• Towns and villages in the Yass Valley have already experienced water quality issues due to drought and heatwave conditions. Any increase in these will have flow on effects to water quality and availability for the Yass Valley.⁴⁰

Actions taken or proposed :

• No actions have been taken or proposed for to address heatwave risks within the LGA.

 Tsunami

• Tsunami’s can be generated by a number of causes, however, undersea earthquakes are the most likely to generate such an event. Tsunami waves can run up beyond the high tide mark causing significant damage to coastal areas.

Actions taken or proposed:

• No actions have been taken or proposed for to address storm and cyclone risks within the Council area.

 Earthquake

• The State Disaster Mitigation Plan identifies Yass Valley Council as having the highest earthquake risk for the social environment (with Upper Lachlan Shire in second and Weddin Shire in third).
• Based on the potential event probability, as provided by Risk Frontiers, annual average loss of residential, commercial and industrial buildings from flood in the LGA is 10 per cent under a RCP 4.5 scenario. This accounts for a low probability of occurring but a high financial cost consequence of earthquake activity; and
• In 1886, an estimated magnitude 5.5 earthquake occurred near Yass (which was also reportedly felt in Queanbeyan) which caused damage to infrastructure in the township. ⁴¹

Actions taken or proposed:

• No actions have been taken or proposed for to address storm and cyclone risks within the Council area.