WMAwater conducted an investigation into the known hydrologic issues in the Bellinger, Kalang and Nambucca catchments. This area of the NSW coast has presented a range of challenges for a number of studies where problems have been encountered matching rainfall runoff modelling with flood frequency results. The Lower Bellingen River Flood Study (PDW, 1991) which covered the Bellingen and Kalang System needed to adopt a larger than standard aerial reduction factor to fit the results of the flood frequency analysis. Similar issues were found on the nearby Nambucca Catchment. WMA analysed rainfall records to create new IFD estimates for the region. As part of the study WMA also investigated the rating curves for key gauges in the region and developed new rating curves. The revised hydrologic models developed as part of this study will provide the design inflows to be used for future studies.

Comparison of regional hydrologic methods.

Comparison of regional hydrologic methods.