In this lab, I worked with both spatial and tabular datasets to perform an analysis of areas in Vancouver at risk of a 10-metre wave. The map below details the total area threatened by a 10-metre sea level rise, as well as the roads affected and locations for tsunami warning signs.
Given a shapefile of Metro Vancouver’s shoreline, I was able to use the buffer tool to apply a 1 km distance to identify inundation areas, and save as a new file, “shoreline1km”. Next, using Vancouver’s digital elevation model, I was able to reclassify a raster file to only display areas under 10 metres. In order to find out where the two criteria intersect, I had to use a tool to convert the raster file into a vector file. I then applied the overlay tool “Intersect” to determine areas 1 km inland AND under 10 metres in elevation. From there, it was possible to use “Clip” and “Select by Location” to locate at-risk land uses, roads, and even facilities like hospitals and schools, which are not highlighted on the above map.
Select by Location allows the GIS user to locate features of one data layer from a source layer. Since the hospitals and schools in my geodatabase were listed as point features, I used “Point in Polygon” to find all facilities within the “Danger Zone” polygon feature, outlined in cyan on Map 1. The following table outlines the facilities in Vancouver in the Danger Zone:
This information is valuable for the Vancouver planning department, who would need to issue notice to the owners of these facilities and insurance companies about the hazards of being located in a flood zone.
By digitizing a polygon from satellite imagery, I also assessed Vancouver’s proposed site in the False Creek Tidal Flats for the St. Paul’s Hospital redevelopment, which lies precariously within the 10-metre danger zone:
The new hospital complex on the Tidal Flats, if the plan is to proceed, must comply to the City of Vancouver’s Flood Construction Levels and Regulations By-Law #10908. The by-law states that buildings intended to be used for habitation, storage of goods, or business (such as a hospital) must be constructed with the lower concrete slab or floor at least 4.6 m above sea level, with additional elevation allowance due to wave run-up. It appears that policy makers do not anticipate 10 metre sea level rises any time soon, and for good reason – Vancouver is protected by Vancouver Island from any major wave action.
Accomplishments:
- Digitized polygon features by creating new vector feature classes in order to add information pertaining to the risk of sea level rises, including signage and site areas, resulting in a detailed, legible mapping of hazard zones in Vancouver.
- Applied a combination of ArcGIS spatial analysis tools, including the select by location tool, to identify over 1588 hectares of at-risk land and 9 facilities affected by a 10-metre sea level rise in the City of Vancouver.
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