Detailed hydrology and hydraulic analyses of 2 major crossings – Harding River and Western Creek – for the proposed new road alignment. HEC-RAS software was used to model water surface profiles of both the upstream and downstream reaches of the rivers. The Harding River site is immediately adjacent to the 2 existing Hamersley Iron railway bridges and involved a difficult crossing at a sharp bend in the river. Various floodway, culvert and bridge options were investigated for each crossing, including a detailed analysis of the stream flow hydrographs for the period of inundation and time of closure. The report presented structure options and performances.