There is growing awareness of the potential risks associated with another Cascadia subduction zone seismic event. We expect large-scale destruction of existing infrastructure, which will not only be very disruptive to human society, it will present new opportunities to reconfigure our current shoreline infrastructure to reduce impacts to habitat forming ecosystem processes. There are numerous habitat problems caused by our current shoreline infrastructure. These include shoreline armoring, which can destroy beach structure and eliminate areas for forage fish spawning and predator evasion; railroads and roads that both block sediment supply from feeder bluffs but that also get blocked from regular landslides; docks and piers that block sunlight and increase predation impacts on smaller fish; and stormwater outfalls delivering pollutants to the nearshore.
To propose options for shoreline infrastructure retrofits and relocations, we could use the motivation of the impending subduction zone seismic event while focusing on desired and possible habitat restoration options. We could also use existing data on known shoreline areas with priority habitat and existing evaluations of at-risk shoreline infrastructure to discover priority geographies for potential future restoration efforts. But to do that, we need criteria to evaluate both current and potential habitat functions and values, and we need different possible future scenarios to include varying scales of potential habitat restoration, as well as options for removal or relocation of damaged infrastructure. The goal is to develop multi-benefit options for consideration in local and regional land use plans.
Using existing information on shoreline area habitats and shoreline infrastructure, an approach to multi-benefit infrastructure relocation and habitat restoration could include these steps:
• Review available literature and reports on the likely destructive impacts to shoreline infrastructure from a large subduction zone seismic event.
• Identify the types of habitat present and describe any available potential for restoration.
• Identify the types of infrastructure present and describe likely infrastructure damage scenarios, infrastructure relocation options if possible, and related land use planning matters as needed.
• Identify a coarse-scale range of options for restoring habitat, abandoning some shoreline infrastructure and either relocating or restoring other vital infrastructure.
• Select a few key geographies for more intensive and detailed evaluation, and engage the relevant local entities to explore local opinions and options.