Hard engineering can cause unintended environmental consequences, such as new erosion and altered sedimentation patterns, that are detrimental to the immediate human and natural environment or along down-coast locations and habitats.
In addition, bulkheads and seawalls offer no filtering for surface runoff, this means that anthropogenic pollutants and chemicals in armored areas may enter coastal waters relatively quickly.
[1] Hard engineering, also called shoreline armoring, comes with other ecological effects on top of habitat loss and increased surface runoff.
For instance, most sea walls and interlocking coastal defense structures are made of concrete, which may lend itself as habitat for invasive species rather than native ones.
These issues arise from hard engineered sea shores, and lead many to believe that living shoreline techniques are far more beneficial ecologically and in terms of long-term erosion control.