The Hillston township is situated within the Lachlan River floodplain and has been affected in the past by river floods. Council established an Urban Floodplain Management Committee and working with the community and State Government has developed an Urban Floodplain Management Plan (2005) (PDF). Implementation of the plan is well advanced.
In 2010 Council constructed the new Hillston Eastern levee. The levee is 1.6 km in length with an average height of 1.5 metres. The project cost about $360,000. The levee protects the town east of the railway line against a 1:100 year ARI flood with additional 'freeboard' as a safety margin against the unlikely event of a probable maximum flood.
In 2018 Council completed a new levee to protect the western section of Hillston, known as the Lachlan Street levee.
Note: A 1:100 year Average Recurrence Interval flood does not mean it will only occur once every hundred years. It means that there is a 1:100 probability (chance) of a flood occurring in any twelve month period. Given the right climatic and catchment conditions more than one 1:100 year flood could occur in any year.