GIS-based spatial zoning for flood inundation modelling in the Murray-Darling Basin

Flood inundation modelling for ecological purpose is important for the Murray-Darling Basin (MDB). It is necessary to divide the basin into hydrologically similar but ecologically independent zones due to its complex topological and hydrological conditions. Pioneer studies in zone delineation at large basin scale have been proven to be successful. However, an outstanding issue identified in these studies is that the topography and hydrological connectivity have not been given enough consideration, which results in the lack of explicit spatial connectivity between zones. In this study, the Australian Hydrological Geospatial Fabric (Geofabric) published by the Bureau of Meteorology of Australia was employed to classify the MDB into eco-hydrological zones. The Geofabric is based on a variety of topological data and has a consistent representation of hydrological features and their connectivity, which are crucial for spatial zoning. Several zoning criteria were established taking into consideration the gauge location, flow data quality and availability, and landscape integrity. Based on these criteria, a number of neighbouring catchments in the Geofabric were combined to generate an eco-hydrological zone. A representative gauge was selected for each zone to best reflect the flow that goes through it. All zones are spatially and hydrologically connected via a stream network. Improved relationships between flow and inundation, and spatial pattern of inundation extent have been achieved compared to the existing zones. It is hoped that the derived zones will be able to help develop floodplain inundation models that can be easily integrated into the Geofabric-based geospatial framework.