Tsunami inundation models are computationally intensive and require high resolution elevation data in the nearshore and coastal environment. In general this limits their practical application to scenario assessments at discrete communiteis. This study explores teh use of moderate resolution (250 m) bathymetry data to support computationally cheaper modelling to assess nearshore tsunami hazard. Comparison with high ersolution models using best available elevation data demonstrates that moderate resolution models are valid (errors in waveheight < 20%) at depths greater than 10m in areas of relatively low sloping, uniform shelf environments. However in steeper and more complex shelf environments they are only valid at depths of 20 m or greater. Modelled arrival times show much less sensitivity to data resolution compared with wave heights and current velocities. It is demonstrated that modelling using 250 m resoltuion data can be useful in assisting emergency managers and planners to prioritse communities for more detailed inundation modelling by reducing uncertainty surrounding the effects of shelf morphology on tsunami propagaion. However, it is not valid for modelling tsunami inundation. Further research is needed to define minimum elevation data requirements for modelling inundation and inform decisions to undertake acquisition of high quality elevaiton data collection.

The quality and type of elevation data used in tsunami inundation models can lead to large variations in the estimated inundation extent and tsunami flow depths and speeds. In order to give confidence to those who use inundation maps, such as emergency managers and spatial planners, standards and guidelines need to be developed and adhered to. However, at present there are no guidelines for the use of different elevation data types in inundation modelling. One reason for this is that there are many types of elevation data that differ in vertical accuracy, spatial resolution, availability and expense; however the differences in output from inundation models using different elevation data types in different environments are largely unknown. This study involved simulating tsunami inundation scenarios for three sites in Indonesia, of which the results for one of these, Padang, is reported here. Models were simulated using several different remotely-sensed elevation data types, including LiDAR, IFSAR, ASTER and SRTM. Model outputs were compared for each data type, including inundation extent, maximum inundation depth and maximum flow speed, as well as computational run-times. While in some cases, inundation extents do not differ greatly, maximum depths can vary substantially, which can lead to vastly different estimates of impact and loss. The results of this study will be critical in informing tsunami scientists and emergency managers of the acceptable resolution and accuracy of elevation data for inundation modelling and subsequently, the development of elevation data standards for inundation modelling in Indonesia.

The Harvey 2008 LiDAR data was captured over the Harvey region during February, 2008. The data was acquired by AAMHatch (now AAMGroup) and Fugro Spatial Solutions through a number of separate missions as part of the larger Swan Coast LiDAR Survey that covers the regions of Perth, Peel, Harvey, Bunbury and Busselton. The project was funded by Department of Water, WA for the purposes of coastal inundation modelling and a range of local and regional planning. The data are made available under licence for use by Commonwealth, State and Local Government. The data was captured with point density of 1 point per square metre and overall vertical accuracy has been confirmed at <15cm (68% confidence). The data are available as a number of products including mass point files (ASCII, LAS) and ESRI GRID files with 1m grid spacing. A 2m posting hydrologically enforced digital elevation model (HDEM) and inundation contours has also been derived for low lying coastal areas.

The 1 second SRTM derived DEM-H Version 1.0 is a 1 arc second (~30 m) gridded digital elevation model (DEM) that has been hydrologically conditioned and drainage enforced. The DEM-H captures flow paths based on SRTM elevations and mapped stream lines, and supports delineation of catchments and related hydrological attributes. The dataset was derived from the 1 second smoothed Digital Elevation Model (DEM-S; ANZCW0703014016) by enforcing hydrological connectivity with the ANUDEM software, using selected AusHydro V1.6 (February 2010) 1:250,000 scale watercourse lines (ANZCW0503900101) and lines derived from DEM-S to define the watercourses. The drainage enforcement has produced a consistent representation of hydrological connectivity with some elevation artefacts resulting from the drainage enforcement. A full description of the methods is in preparation (Dowling et al., in prep). This product is the last of the Version 1.0 series derived from the 1 second SRTM (DSM, DEM, DEM-S and DEM-H) and provides a DEM suitable for use in hydrological analysis such as catchment definition and flow routing.

Removing the topographic effect from satellite images is a very important step in order to obtain comparable surface reflectance in mountainous areas and to use the images for different purposes on the same spectral base. The most common method of normalising for the topographic effect is by using a Digital Surface Model (DSM) and / or a Digital Elevation Model (DEM). However, the accuracy of the correction depends on the accuracy, scale and spatial resolution of DSM data as well as the co-registration between the DSM and satellite images. A physics based BRDF and atmospheric correction model in conjunction with a 1-second SRTM (Shuttle Radar Topographic Mission) derived DSM product released by Geoscience Australia in 2010 were used to conduct the analysis reported in this paper. The results show that artefacts in the DSM data can cause significant local errors in the correction. For some areas, false shadow and over corrected surface reflectance factors have been observed. In other areas, the algorithm is unable to detect shadow or retrieve an accurate surface reflectance factor in the slopes away from the sun. The accuracy of co-registration between satellite images and DSM data is crucial for effective topographic correction. A mis-registration error of one or two pixels can lead to large error of retrieved surface reflectance factors in the gully and ridge areas (retrieved reflectance factors can change from 0.3 to 0.5 or more). Therefore, accurate registrations for both satellite images and DSM data are necessary to ensure the accuracy of the correction. Using low resolution DSM data in conjunction with high resolution satellite images can fail to correct some significant terrain effects. A DSM resolution appropriate to the scale of the resolution of satellite image is needed for the best results.

The 3 second (~90m) Smoothed Digital Elevation Model (DEM-S) Version 1.0 was derived from resampling the 1 second SRTM derived DEM-S (gridded smoothed digital elevation model; ANZCW0703014016). The DEM represents ground surface topography, excluding vegetation features, and has been smoothed to reduce noise and improve the representation of surface shape. The DEM-S was derived from the 1 second Digital Surface Model (DSM; ANZCW0703013336) and the Digital Elevation Model Version 1.0 (DEM; ANZCW0703013355) by an adaptive smoothing process that applies more smoothing in flatter areas than hilly areas, and more smoothing in noisier areas than in less noisy areas. This DEM-S supports calculation of local terrain shape attributes such as slope, aspect and curvatures that could not be reliably derived from the unsmoothed 1 second DEM because of noise. A full description of the methods is in progress (Gallant et al., in prep) and in the 1 second User Guide. The 3 second DEM was produced for use by government and the public under Creative Commons attribution. The 1 second DSM and DEM that forms the basis of the product are also available as 3 second products (DSM; ANZCW0703014216, DEM; ANZCW0703014182, DEM-S; ANZCW0703014217). <strong>Please note that all 1 second products are available for GOVERNMENT USERS ONLY.</strong>

The 2011 National Elevation Audit is a series of maps illustrating the areas where elevation data has been captured or will be completed until the end of 2012 and their relative vertical accuracy.

To be completed

The 9 second DEM derived streams are a a fully connected and directed stream network produced in rastor and vector fomats by Australian National University. This product is the raster format, for the the vector product please refer to the Bureau of Meterology's Geofabric Website (http://www.bom.gov.au/water/geofabric/index.shtml). It is built upon the representation of surface drainage patterns provided by the GEODATA national 9 second Digital Elevation Model (DEM) Version 3 (ANU Fenner School of Environment and Society and Geoscience Australia, 2008).

Data was collected by selecting the highest point(s) in each geographical area of 30 minutes of latitude by 30 minutes of longitude. Elevations are recorded in feet and metres (always rounded up). Information is derived from 1:1 Million scale World Aeronautical Charts. Note: This is not regularly gridded data.