A Geospatial Framework for Mapping Tsunami Hazard, Inundation, and Exposure in Coastal British Columbia, Canada

Tsunamis pose a significant and ongoing threat to communities along British Columbia's coast. The tsunami-generated waves and currents, combined with climate-change-driven sea level rise, can cause extensive damage to coastal infrastructure, threaten vessels, and, in severe cases, result in the loss of life. British Columbia is particularly vulnerable due to its proximity to the Cascadia and Alaska-Aleutian subduction zones. This methodology introduces a geospatial framework for generating tsunami hazard, inundation, and asset-at-risk maps to inform communities about potential tsunami impacts and guide emergency preparedness plans. The framework described in this methodology converts numerical tsunami simulations generated in FUNWAVE-TVD into a GIS-compatible format using Python-based processing that includes unit conversion, horizontal datum alignment, and the creation of gridded points. Regional-scale hazard maps are generated as continuous raster surfaces confined to overwater areas, with values interpolated from the gridded points using inverse distance weighting (IDW) to represent maximum wave amplitude (hmax) defined as wave height above a still-water surface and maximum wave current speed (umax) defined in knots. 

Localized inundation mapping is achieved by integrating a 10m resolution tsunami model with a 1m resolution coastal digital elevation model that was developed from up-to-date high-resolution bathymetric and LiDAR data. Raster-based analysis defines inundation extents and derives water depth surfaces by intersecting the modelled wave heights, referenced to the Canadian Geodetic Vertical Datum of 2013 (CGVD2013) and adjusted for tidal and sea-level-rise variations, with ground elevation. This workflow enables the representation of coastal inundation and supports consistent hazard classification across multiple tsunami scenarios. The final stage of the framework involves deriving asset-at-risk products that identify building structures and road networks that are potentially susceptible to damage or compromise from tsunami-induced flooding. Asset exposure is classified using a hazard index based on inundation depth and wave velocity,  and is visualized on a graduated scale from low to high risk.

These methods developed for the British Columbia coast provide a reproducible, transferable workflow for integrating numerical tsunami model results into multi-scale mapping products applicable to different tsunami models created from varying source types and influenced by differing coastal topography. These products inform coastal communities and stakeholders about potential tsunami risks and support evidence-based decision-making.