Haida Gwaii Coastal Flood and Erosion Study
In 2020, in partnership with other civic communities on Haida Gwaii, the North Coast Regional District made application to the Community Emergency Preparedness Fund (CEPF) to undertake the Haida Gwaii Coastal Flood and Erosion Study project, which included mapping of hazards such as coastal storm flood, tsunami iundation and shoreline erosion susceptibility in the NCRD communities of Sandspit and Tlell, B.C., given 1 to 2 meter sea-level rise scenarios. Tsunami iundation mapping was also completed in Tow Hill.
In September 2023, the North Coast Regional District and Northwest Hydraulic Consultants Ltd. conducted a Sandspit, Tlell, and Towhill Coastal Flood and Erosion Study Workshop. Please click here for the slides that were presented at the workshop.
Northwest Hydraulic Consultants Ltd. completed the following reports for each community:
Haida Gwaii Coastal Flood and Erosion Study Planning for Sea-Level Rise and Tsunami Hazards
All residents of Haida Gwaii live in communities near the shoreline and depend on critical infrastructure that is subject to potential flooding and erosion from ocean processes. Each community is increasingly vulnerable to rising sea levels. Shoreline erosion is now occurring at several locations and will accelerate and expand to affect more of the coastline as higher sea levels promote the effects of the waves reaching higher up on the shoreline. In addition, many residents are at risk of being affected by tsunami's, particularly given the island's exposure to the Alaskan-Aleutian and the Cascadia subduction zones.
Sandspit Community Summary Report
This report summarizes the coastal flood and erosion hazards identified in this project for the community of Sandspit on Haida Gwaii. This report has been revised to include additional detail describing shoreline erosion processes. The objectives of the study were to predict the potential future effects from two independent natural hazards - tsunamis and coastal flooding from storm waves - when sea levels are predicted to be higher. An assessment of the shoreline susceptibility to erosion was also completed.
Tlell Community Summary Report
This report summarizes the coastal flood and erosion hazards identified for the community of Tlell on Haida Gwaii. This report has been revised to include additional detail describing shoreline erosion processes. The objectives of the study were to predict the potential future effects from two independent natural hazards – coastal flooding from storm waves and tsunamis – when sea levels are expected to be higher. The results of the study are intended to inform communities as they make long‐term community planning and governance decisions.
Tow Hill Tsunami Inundation Mapping
Digital Elevation Model Metadata Report
This report discusses the creation of integrated topographic bathymetric digital elevation models (DEMs) and tsunami models to support risk and vulnerability assessment, as well as improve collective resiliencies of these coastal communities.
This report provides a summary of the meteorological and oceanographic (meocean) analysis to better understand the governing conditions offshore from Haida Gwaii. These results inform the overall study conclusions, which are described in the main report, Haida Gwaii Coastal Flood and Erosion Study – Planning for Sea-Level Rise and Tsunami Hazard.
This report provides a summary of the approach used to estimate the combined water levels and shoreline wave effects that form the basis of the Flood Construction Level (FCL) for hazard mapping. The coastal FCL is comprised of a water level that is a combination of the designated flood level (astronomical tide and storm surge) as well as wave effects (or wave runup).
Co-Seismic Tsunami Hazard Assessment for Haida Gwaii
This report summarizes the modelling analysis performed to estimate the tsunami hazard by two distant sources at each of these communities. Detailed tsunami simulations were carried using FUNWAVE-TVD model, a well-established tsunami prediction tool with demonstrated accuracy. In the following sections, the study area and tsunami sources are firstly described.
