Greening the Fight against Sea Level Rise: Grey vs Green Approaches

Masters thesis exploring relative merits and trade-offs between soft (green), hard (grey), and hybrid (mixed green and grey) approaches to coastal flood resilience.

The purpose of this paper is to investigate the relative merits and trade-offs between soft (green), hard (grey), and hybrid (mixed green and grey) approaches to coastal flood resilience for use by decision-makers in the City of Vancouver, with a focus on Kitsilano Beach (one of the flood-prone areas identified in the City of Vancouver Coastal Flood Risk Assessment). The options considered are: beach nourishment, soft-shore armouring, a traditional dike, a green dike, and a sand dike with sediment fill. Results from the analysis may be informative to other flood-prone areas outside Kitsilano, where investment decisions for coastal flood resilience are to be faced by the CoV and neighbouring municipalities in the coming decades.

The analysis uses mixed methodology (primary expert interviews and secondary benefit transfer valuations) to assess the relative merits and trade-offs between soft, hard, and hybrid approaches to coastal flood resilience. Results suggest that while hybrid infrastructure may require 2 to 3.5 times the capital costs of hard infrastructure, it is equally effective at providing floodrelated damage protection from sea level rise, and many times more effective at enhancing aesthetic, amenity, and ecological values.

In the near term, it is recommended that the City of Vancouver invest in soft-shore armouring at Kitsilano Beach, as well as commence a technical feasibility assessment for the implementation of a sand dike with sediment fill for future preparedness.