The flood study is the formal starting process of defining management measures for flood liable land and represents a detailed technical investigation of flood behaviour. This flood study deals with flooding at Cowra and Gooloogong, two urban centres located in the middle reaches of the Lachlan River downstream of Wyangala Dam. The study has been supervised by the Floodplain Management Committee comprising representatives of Cowra Council, DLWC, SES and local community groups.

This investigation deals with the definition of flood levels and flow patterns at Cowra and Gooloogong for a range of floods varying in frequency between 5% and 0.5% AEP (annual exceedance probability), as well as the extreme flood event. The Cowra investigation updates the study carried out in 1983 by the then Water Resources Commission (WRC), now Department of Land and Water Conservation (DLWC), for the preparation of the Cowra Flood Inundation Map. No formal flood investigation has previously been carried out for Gooloogong although the Floodplain Management Study for the Lachlan Valley and the Flood Atlas prepared by Rankine and Hill in 1983, identified the approximate extent of flooding for a typical major flood event.