Shoreline armoring and its impact
January 5, 2010 · Updated 10:49 AM
Shoreline modifications like roads, boat ramps, and bulkheads, can directly damage nearshore habitat by physically covering the inter-tidal habitat. Armoring also changes the natural sediment processes, cutting off the migration of vital sediment to our beaches from upland sources, while at the same time concentrating wave energy onto the beach itself at the base and edges of the structure. The redirected wave and current energy increases erosion of the beach and intertidal area, eventually removing the fine sediments until only hardpan or bedrock remains. Over time this results in shorelines that are no longer suitable habitat for eelgrass or forage fish spawning. Armoring also leads to lowered beaches that are difficult for people to access and can actually increase erosion problems for neighbors.
In San Juan County, there are limited forage fish spawning grounds and they are very vulnerable to shoreline infrastructure and development activities. A recent study found that shoreline modification can reduce the survival rate of surf smelt embryos as much as 50 percent.
Alternatives to shoreline armoring: Soft shore protection and restoration techniques can be used to protect property and forage fish spawning habitat and coastal processes in many cases. Indigenous materials such as gravel, sand, logs, and root masses are used to enhance natural beach shape and processes. Soft shore armoring is a successful long-term method of addressing the erosion concerns that led to shoreline armoring while at the same time restoring degraded habitat.
Coastal Geologist Jim Johannessen, an expert in shoreline protection and restoration that works on many projects with FRIENDS, says that in addition to the benefit of protecting private property along shorelines, soft shore protection methods offer direct benefits to nearshore marine environments. These include: restoration of forage fish spawning habitat, introduction of woody debris, shading, revegetation and increased shoreline complexity.