The AGL Loy Yang Brown-Coal Mine is undergoing progressive rehabilitation and plans on converting the mine into a pit lake. Converting the mine into a pit lake may take several decades, there are many scenarios that may occur in this period that pose a risk to the slope stability. A model that can predict the slope behaviour under different conditions is needed to accurately determine the long-term slope behaviour. Capturing the possible long-term behaviour requires intensive computational power. A strategy to develop a Reduced Order Model (ROM) is presented to capture the likely slope behaviour with less computational power.