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Hard engineering involves the construction ofhydraulic structures to protect coasts fromerosion. Such structures includeseawalls,gabions,breakwaters,groynes andtetrapods.
Hard engineering can cause unintended environmental consequences, such as newerosion and alteredsedimentation patterns, that are detrimental to the immediate human and natural environment or along down-coast locations andhabitats.
Seawalls andbulkheads may have multiple negative effects on nearshore ecosystems due to the way they reflect wave energy instead of dissipating it. Energy from reflected waves can cause a scouring effect on substrate below the structure, resulting in loss or displacement of sediment. Over time, this effect may lead to a decrease in the size of intertidal and nearshore habitats. This effect is also known ascoastal squeeze. In addition, bulkheads and seawalls offer no filtering forsurface 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 ofhabitat loss and increased surface runoff. Structures that are built between land and sea are usually made of material not native to shoreline ecosystems. 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 structures also impede shoreline access, blocking some or all species from accessing refuge on dry land. In these armored areas, nutrient exchange between tidal and riparian ecosystems is threatened or cut off entirely. 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-termerosion control.[2]
Examples of hard engineering include:
