Mr Scott Langtry¹, Dr Ryan Alexander¹, Dr David Wright¹, Mrs Nuala Page³ 

¹RPS, West Perth, Australia

Development of coastal land must consider the vulnerability of the asset to hazards of erosion, inundation and property damage generated by the sea during storm events. The vulnerability of the coastal zone of Western Australia to more frequent and/or more severe storms is expected to increase in the future due to sea level rise and climate change effects. Where the coastal zone is currently undeveloped, decision-makers require reliable coastal hazard assessments to weigh up the merits of displacing naturally occurring habitats. This presentation describes the procedures followed to quantify inundation and water flow over a naturally occurring wetland habitat on the North West Shelf of Australia subject to contemporary tides, sea level rise and cyclone forcing. The relatively large and flat study area, spanning ~60 km of coastline, is currently in a natural state. The area has a low foredune intersected by multiple, highly-branched creeks reaching into extensive salt flats. The area is vegetated with mangrove forests over the foredunes, backed by wetlands and crusting algae over the salt flats. Initial site investigations revealed that extensive lakes develop over the salt flats but will only persist for time scales of hours and only during higher spring tides, with rapid filling and draining from and to the sea. A digital elevation model developed from high-resolution LIDAR surveys formed the basis of an inundation model, forced by tidal and offshore sea level anomalies, atmospheric pressure, and wind. The inundation model was forced by non-storm conditions for both contemporary and projected sea levels, and was also coupled to forcing generated by a cyclone model that had been applied in a stochastic manner to simulate historic cyclones and synthetic variants.

Biography:

Ryan Alexander has extensive experience as a research and consulting environmental engineer specialising in the assessment of contaminant fate and transport in aquatic systems, hydrodynamic modelling, data analysis, and the coupling of hydrodynamic models with sediment, oil and ecological pollutant models in coastal and offshore environments. Ryan is an experienced numerical modeller and has sound theoretical and practical experience in fluid mechanics, biological aquatic processes, and discharge from jets and plumes.