The upper catchments of the Manilla River are located to the northwest of Tamworth in the New England region of the NSW. The river drains a large (771 square kilometres) catchment before flowing through the town of Barraba. The Manilla River headwaters are located near Split Yard Mountain in the Nandewar Range and drains in a north easterly direction to the Plumthorpe area, before turning south-east towards the town of Barraba. Approximately 20km south of Barraba, the Manilla River discharges into Split Rock Dam (400GL).

The primary objective of this study was to define the main-stem flood behaviour under historical conditions and design flood behaviour under existing and future climate conditions in the study area. The study produced information on flood levels, depths, velocities, flows, hydraulic categories, and provisional hazard categories for a full range of design and historical flood events. In addition, the study produced estimates of flood damage.