Coastal inundation modelling for Busselton, Western Australia, under current and future climate

Abstract

Geoscience Australia, the Western Australian Department of Planning and the Western Australian Planning Commission have collaborated through this study to develop a regional-scale inundation model capable of simulating combined storm tide and riverine flood scenarios within current and future climate conditions (sea-level rise influences only). Modelling scenarios were applied to the Busselton region of Western Australia. The ANUGA hydrodynamic model (https://anuga.anu.edu.au/) was run based on a Digital Elevation Model (DEM) and inputs from a regional storm surge model (GEMS GCOM2D) The maximum inundation depth and momentum values were identified in ArcGIS post processing. DEM used within ANUGA: Triangular mesh created by/within ANUGA from a regular grid (1 m horizontal resolution). The input grid was based on elevation data with varing accuary: onshore and offshore LiDAR, Navy soundings and 1 second SRTM DEM. The derived triangular mesh consisted of smaller triangles (max 5m^2) around the man-made drainage channels and larger triangles around the remainder of the study region (max 350m^2) Regional storm input: Temporal (i.e. storm characteristics through the simulation time) were extracted from the regional storm modelling (GEMS GCOM2D model) results for point locations along the Busselton-Dunsborough coastline. ANUGA model variables Some key variables set within the Python code were: minimum_storable_height = 0.10m, mannings coefficient of friction = 0.03, 12 minute modelling time steps, 64 CPUs were used (variations were identifed between the results depending on the number of CPUs specified. The 64 CPU results were in the middle of the field (range from 8 to 128 CPUs). Broader detail of the methods applied within this project are within the technical methodology document. Also see the GA Professional Opinion (Coastal inundation modelling for Busselton, Western Australia, under current and future climate)