These data describe quantitative exposure indices generated using cartographic fetch methods on a 0.01 degree grid across temperate Australia (South Australia, Victoria and Tasmania). Two indices are reported: openness and bathymetry-altered fetch. Openness is a measure of the distance of a site to the nearest coastline in all directions and describes potential exposure to locally generated seas and undefined swell. Bathymetry-altered fetch attempts to account for the attenuation of wave energy as waves move into shallow waters and encounter friction with the seafloor.

The Statewide Marine Habitat Map 2023 was developed by DEECA applying novel machine learning methods that model and predict habitat distributions as well as a mosaic of former mapping products (listed below). The Statewide map represents 24 marine and coastal habitats complexes at Level 3, Victoria's Combined Biotope Classification Scheme (CBiCS) described by Edmunds and Flynn (2015, 2018; 2021). The final map comprises of 83% its area from predictive modelling, with the remaining 17% of area from synthesised existing habitat maps. Predictive Model: A total of 32,998 habitat survey sites (ground-truth records) were used within the model, along with 28 environmental properties mapped at a 10m resolution (including a Digital Elevation Model DEM (VCDEM2021), computed benthic terrain characteristics (toolkit: Walbridge et al. 2018), Chlorophyl a (IMOS 2000a), Sea Surface Temperature SST (IMOS 2000a), Net Primary Productivity NPP (IMOS 2000b), Sediments (Geoscience Australia; Li et al. 2011a,b,c), waves (Liu et al. 2022). To predict the distribution of habitats across Victorian waters the powerful and flexible Random Forest machine learning algorithm was applied. Random Forest is an ensemble model using bagging as the ensemble method and decision trees as the individual model (Breiman 2001). The modelling produced an accuracy (Out-of-bag) of 89%. Map Synthesis: A mosaic of former mapping products that provided higher resolution mapping by aerial imagery, field observations and high-resolution modelling were integrated into the map, classifying habitat according to the CBICS habitat classification scheme at level 3. Assessed and synthesised maps and citations include: Corangamite Coast Marine Habitat December 2009 (ANZVI0803005530); East Gippsland Marine Habitats November 2009 (ANZVI0803003974); Discovery Bay Marine National Park habitat mapping 2006 (ANZVI0803004053); Portland Coastal Habitats (ANZVI0803004236) ; Corner Inlet Mapping Marine National Park North and South 2004 (ANZVI0803004051) ; Merri Marine Sanctuary 2004 (ANZVI0803004058); Western Port Bay Biotope Mapping Fathom Pacific (2016) CBiCS-Mapping. Central Victoria Coastal Habitats (ANZVI0803004135); Mallacoota Coastal Habitats (ANZVI0803004235); Western Port Rhodolite (ANZVI0803005430) & Western Port Biogenic Reefs; Port Phillip Bay Habitat Map 2021 (ANZVI0803009278); Saltmarsh and Mangrove Habitats; DELWP 2021 Statewide Marine Habitat Map 2021 (ANZVI0803009286) and relevant citations: Ball (1999), Ball et al. (2010). Ball & Blake (2007a), Ball & Blake (2007b), Blake and Ball (2001), Blake et al. (2013), Boon et al. (2011), Cohen et al (2000), Deakin Marine Mapping (Zavalas, R et al. 2018), DELWP (1994), Edmunds &Flynn (2015), Fathom Pacific (2020), Ford et al (2016), GeoHab Victoria Estuaries Geomorphology (2010), Ierodiaconou 2007, Ierodiaconou et al. 2018, Mazor et al. (2021), Monk et al. (2011), Poore (1992), Roob and Ball (1997), Victoria Department of Transport (1999), Young et al. 2022, Zavalas, R et al. 2018. Applications: The Statewide Marine Habitat Map 2023 provides broad habitat complexes across the state and provides greater knowledge of the ecological diversity across Victoria¿s waters. The map should be used at broad scales of >25 m, and where information of larger habitat complexes is needed. This work can support the management of large-scale habitats, their condition, marine spatial planning, strategic management prospect (SMP), FeAST risk assessments, and other broad scale applications to support management decisions across Victoria. The habitat model and resulting map provides an updated broad-scale habitat map across Victoria¿s state waters and provides a baseline for future data to build upon.