Spatial Assessment of Estuary Shoreline Erosion Susceptibility
Authors: Christine Arrowsmith; Georgina Race
Abstract: The Gippsland Lakes is a system of coastal lagoons sheltered behind sandy barriers, with a total length of shoreline of over 260km. A study of the susceptibility of this shoreline to erosion under current sea level conditions and a range of potential sea level rise scenarios has been undertaken using an integrated spatial framework. The approach involved the development of a spatial data and analysis GIS model to interpret available data. Numerous spatial data sets have been integrated in the model under three thematic areas; physical, environmental and biological.
- The physical theme combines the fabric and form of the shoreline, based upon the Smart Line analysis methodology developed by Sharples et al (2009) but also including the presence of artificial structures.
- The environmental theme combines the effects of wave and current exposure on the shoreline based on detailed hydrodynamic modelling.
- The biological theme brings together information on vegetation communities and land use.
A risk score was applied to each individual and combined parameter, to produce three thematic scores. The framework was designed to allow the option to weight the inputs separately to produce the integrated shoreline erosion susceptibility mapping data layer. The analysis was designed to allow the weighting exercise to be undertaken iteratively to test the sensitivity of the analysis and to view the outputs from different weighting options. The outputs were also compared to previous local shoreline erosion assessments around the lakes which provided the opportunity to benchmark the scores and weightings. The physical form was found to be the dominant theme, particularly for flat to moderately sloping sandy shores. Waves, currents and vegetation communities showed increasing impacts on shoreline erosion susceptibility under sea level rise conditions.