Coastal dunes with resistant cores

摘要

Hybrid shore protection projects combine hard structures with beaches, sand dunes and vegetation, mimicking the appearance and function of natural landforms. These advantages can also accrue to structures built as primary protection that eventually become covered by sand following natural accretion, artificial nourishment or burial by earth-moving equipment. This study reviews the advantages and disadvantages of dunes designed and built as hybrid structures using geotextiles, gabions and clay as core elements and dunes that eventually form over traditional beach protection structures that are built independently of a sand cover. Dunes constructed with hard cores can be considered soft solutions that overcome restrictions by regulatory agencies against hard shoreline armoring, but most hybrid designs are low-cost temporary solutions. Protection plans should also include subsequent protection actions that address long-term needs. Hard cores should be placed close to the human facilities to be protected to increase space for naturally functioning landforms and habitats seaward. Mechanical reburial of exhumed cores should occur as soon as possible to help prevent damage to them, reestablish habitat and aesthetic value, reestablish safe access between beach and upland for native fauna and beach users, and keep nature and the need for restoration in the minds of beach users. Keeping the fronting beach wider by artificially nourishing it can protect the structure from exhumation, provide a larger sand surface for dune buildup by aeolian processes and provide space for a more natural environmental gradient across the shore.