VCMP Sites - Shorelines
The Shorelines dataset features short-term and long-term shorelines across sites monitored by the Victorian Coastal Monitoring Program (VCMP) along Victoria's coastline, spatially represented as polyline data.
The VCMP drone survey short-term outputs include shorelines for each survey, taking the ‘shoreline’ as the +1 m AHD contour for Open Coast sites, and +0.5 m AHD contour for large bay sites.
Output products include 1m Digital Surface Models (DSM) and Orthophotos (vegetation is included in
UAV data).
- Vertical uncertainty for the output digital surface model (DSM) is estimated at 0.1 m.
- The shoreline proxy is defined as the point at which each transect first intersect a given contour (m,
AHD): 1.0 m AHD for open coasts and 0.5 m AHD for bay sites
- Intersection points are joined alongshore to create a shoreline, noting the alongshore spacing (30-m)
may be too low to define complex, small-scale features.
- Assuming a beach face slope of 1-in-10, a 0.1 m vertical uncertainty in the survey DSM equates to
cross-shore uncertainty of 1 m in shoreline position.
Digital Earth Australia (DEA) coastlines
A mean annual mid-tide shoreline is extracted from satellite imagery using sub-pixel identification
methods, for the period 1988 to 2021, at 30-m alongshore spacing (Bishop-Taylor et al., 2021).
- DEA shorelines have an estimated uncertainty of 1-3 m, with a precision limit on shoreline trends of
0.31 m/yr, i.e., trends below this threshold are insignificant.
- DEA have known issues around cliffed areas, leading to higher (unconstrained) uncertainty in some
cliffed areas. DEA outputs in such areas should be treated with caution.
Aerial Imagery Shorelines
Aerial images are hosted and geo-rectified by DEECA's Coordinated Imagery Program. Based on control point checks by VCMP, newer images (approx. post-2000) are estimated to have horizontal uncertainty of 3-m or less. Older
images (pre-2000) can have greater uncertainty, estimated at up to 10-m. Older images (<1960)
may have larger errors (unconstrained) and should be treated with caution.
- Backshore line: Extracted for open coast and bay sites. Identified manually as the onshore extent of
the active sandy beach. Depending on morphology, the backshore line may be defined vegetation,
dune toe, cliff toe and / or a coastal protection structure (sea wall or revetment).
- Shoreline proxy line: Extracted for bay sites only (with low wave energy). Identified manually as the
instantaneous wet/dry line, with no tidal correction.
- Sites with larger tidal ranges (e.g., Cowes) would be expected to have larger uncertainty in shoreline
position and caution is advised.
All shoreline data (short-term VCMP drone and long-term DEA satellite) are interpolated to the same set of 30-m spaced transects, based on the Digital Earth Australia 2019 product.
More information about the Shoreline dataset and other datasets generated from the Victorian Coastal Monitoring Program can be found at https://www.marineandcoasts.vic.gov.au/__data/assets/pdf_file/0041/688397/VCMP_Sites_MetadataReport_Oct2023.pdf
