The first step in any flood risk planning process is to identify and understand the hazard; you can’t plan to mitigate risk without knowing what the risk is. This is most definitely true for Metro Vancouver as we face sea level rise. As yet, there are no government-supported, publically-available flood maps of the region that show potential future inundation areas. However, several municipalities in the region have recognised the issue and have recently updated flood construction levels (FCL) for coastal areas to include 1 m of sea level rise. Most recently, the City of Vancouver, updated their FCL to 4.6 m for coastal areas. So, just to start the conversation we thought it would be a good idea to map the parts of the Lower Mainland that might be under water if we were flooded from the ocean at an elevation of 4.6 m GSC.
We used freely available datasets (i.e. not the highly- accurate elevation information that would be ideal for creating flood maps) from GeoBase Canada (now Open Government Canada). Specifically, we used TRIM data to develop a simple Digital Elevation Model (DEM) using the rather wonderful opensource QGIS. We then simply projected a 4.6 m plane across the DEM to map areas that would potentially be under water in a future storm. This means that we have not modelled actual pathways that water might take overland; the water is not blocked by dikes in this scenario, nor is it pushed further inland by wind or waves or other hydraulic forces. It is a simplistic analysis designed to start a conversation.
The results, presented below, are startling. There are huge swaths of our region that are blue: Richmond, Delta, Surrey and I think more surprisingly Port Coquitlam, Pitt Meadows and Maple Ridge. The implications of this are great (see Tamsin Lyle’s op-ed in the Vancouver Sun for some of the implications). We need to act on this threat soon. First, by better understanding our hazard and risk as a region and second by developing a holistic plan to reduce our risk. Ebbwater will continue to add to our understanding of the flood hazard and risks as we are able to track down suitable data sets to help inform the analysis; keep your eyes on our pet projects page! In the meantime, why not start a conversation with your neighbours, your colleagues, your friends about what sea level rise might mean to you and your community?
November 2016 Update – After several years of work the City of Vancouver released their sea level rise strategy. This project examines the hazards and risks from sea level rise for the municipality, and sets out a plan to manage and mitigate the risk.