Digital Elevation Model of Chalky Sound and neighbourhood, New Zealand

Purpose: numerical modelling of tsunami For the purpose of studying the impact of the 25 March 2025 Puysegur tsunami in the southwest of New Zealand South Island, a high-resolution digital elevation model (DEM) of the central part of Fiordland covering Chalky Sound and its neighbourhood, including the location of the Puysegur tsunami gauge (PUYT), has been built using four different types of data. They include: - NZ 8m Digital Elevation Model (LINZ, 2023) - Depth contour polyline (Hydro, 1:4k - 1:22k, LINZ, 2023) - Sounding points (Hydro, 1:90k - 1:350k, LINZ 2023), (Hydro, 1:22k - 1:90k, LINZ 2023), (Hydro, 1:4k - 1:22k, LINZ 2023) - Digitized and georeferenced nautical chart of Chalky and Preservation Inlets - South Port (LINZ, 2023), Breaksea Sound and Dusky Sound (LINZ, 2022), and Western Approaches to Foveaux Strait (LINZ 2022). The data showing the highest resolution has been kept in priority. The depth values in the sounding points and depth Contour Polyline datasets are vertically referred to LAT (Lowest Astronomical Tide). For tsunami modelling purposes, all bathymetric and topographic data must be referenced to the same known vertical reference (e.g., Mean Sea Level or MSL). To standardize the datasets, we apply a vertical correction of MSL-LAT which in this case equals -1.4 m (Standard port tidal levels provided by LINZ[1]). We consider that the 8 m resolution DEM from LINZ (2023) is referenced to MSL. The compilation of data has been interpolated to a regular spatial resolution 0.0001° (~10 m). The data interpolation processes have been done using the kriging interpolation method. For more information about this method, see for example Oliver and Webster (1990). [1] https://www.linz.govt.nz/guidance/marine-information/tide-prediction-guidance/standard-port-tidal-levels