Do the studies contradict each other?

No, the results of the two studies are consistent. The 2020 study is an update and refinement of a hazard identified in the 2019 study. The CVRD was able to obtain high-resolution LiDAR for the study area allowed for a firmer definition of hazard areas. The 2019 Ebbwater / Palmer study was based on provincial TRIM mapping (visually inferred 10 meter contours) and historical air photos. It identified the hazard at a 1:15,000 scale, dividing the landscape into large areas with a hazard score based on the likelihood of a landslide impacting that polygon. Within each hazard area, the hazard varies. The 2020 Palmer / Stantec study is based on the new LiDAR which allows mapping at a much finer scale than was previously possible (digital 10 cm accuracy). The modelling of debris flow runout enables us to map a line beyond which no modelled landslides travelled.

A comparison of the results shows the 2020 runout limit cuts across various 2019 hazard polygons. For example, a high hazard polygon was identified in the area of Creekside Drive with an Annual Encounter Probability equating to 1:3,000 years. It is understood that within this polygon the hazard varies, generally increasing closer to the base of the steep slopes and within gullies. Further geotechnical investigation is required to show where, within the polygon, the higher hazard areas are located and what the actual risk is at the site level. What the 2020 results do, is a first step in this further geotechnical investigation. The runout limit runs parallel to the slope, bisecting the hazard polygon. It defines parts of the polygon (below the line) in which the hazard is below the 1:10,000 year threshold. In the rest of the polygon, there may be a hazard due to landslides – in these areas, further geotechnical investigation would be required to define the risk.