BMT was commissioned by Richmond Valley Council (Council) to undertake the ‘Richmond Valley Flood Study’. The study has been delivered with financial support from the New South Wales (NSW) State Floodplain Management Program and has been undertaken in accordance with the principles of the NSW Government’s Flood Prone Land Policy. The overarching aim of the study is to provide updated flood mapping across Council’s Local Government Area (LGA) for a range of design flood magnitudes, expressed in terms of the annual exceedance probability (AEP). To achieve this, new hydrologic and hydraulic models have been developed taking advantage of the latest advancements in modelling software and the latest available topographic data. This has allowed the Richmond River floodplain to be mapped at a higher resolution and greater extent than that in prior flood studies, with approximately 85% of the LGA’s floodplains now mapped. Key parts of the study are to- ~ update catchment hydrology to conform with the Australian Rainfall and Runoff 2019 (ARR2019) guideline (Ball et al, 2019) which represents current best practice in flood estimation within Australia, ~ have a single consistent flood study across the LGA, which replaces the Casino Flood Study (1999), Richmond River Flood Study (2010), Evans River Flood Study (2014), and incorporates flood modelling from the Pacific Motorway bypasses of Woodburn and Broadwater, and ~ include a climate change scenarios with all the design floods. The report documents the study along with the updated modelling and mapping outputs.