This study includes consideration of the plateau catchments and flooding behaviour of Emigrant Creek, Maguires Creek, North Creek and the lower Richmond River. These catchments are dominated by rolling topography and hills with slopes ranging from 5% to 30%. The model also includes three minor tributaries of Emigrant Creek; Sandy Flat Creek, Chilcotts Creek and Duck Creek.

The Ballina Floodplain Management Study of 1997 (the previous study) was based on one-dimensional hydraulic modelling of the Richmond River and local catchments. In order to progress the preparation of a Floodplain Risk Management Study and Plan for Ballina, Ballina Shire Council expressed the need to embark on more advanced two-dimensional (2D) hydraulic modelling and geographic information systems (GIS) based flood mapping. This study is to update these two components of the previous study. Inherent in the modelling update is updated data collection.

This report is a technical document designed to describe the development and simulation of the flood model and present the simulation results as GIS-based flood mapping. A range of calibration and design events under existing floodplain characteristics and approved future conditions will be considered. This study will form the basis for the preparation of a Floodplain Risk Management Study and Plan for Ballina.