Carrathool Shire Council, through the Hillston Floodplain Management Committee, is developing a floodplain risk management strategy and plan for the town of Hillston. The Lachlan River flows through Hillston. Several overland floodways carry flow in large floods. Mainstream flooding can be caused by the river or its floodways, singly or in combination. Flooding due to local stormwater runoff can also occur but is not considered in detail in this study. The floodplain which this study covers, extends to the estimated limit of the Probable Maximum Flood (PMF). Because of the difficulty of estimating the PMF this study uses an arbitrarily defined extreme flood (EF) as described later.

This Floodplain Risk Management Study defines the nature and extent of the flood hazard in the catchments. It also identifies and assesses strategies and measures aimed at reducing the impact of flooding on both existing and future development, and measures to prevent future development from making flooding worse. The results of this Floodplain Risk Management Study are used to prepare a Floodplain Risk Management Plan (FPMP). The objective of the FPMP is to establish a cost-effective floodplain management strategy for the area and to recommend a programme for implementation of the Plan.