Coastal erosion is a natural process where many shorelines retreat over long periods of time from sea-level rise, wind and water, and wave action. While the shoreline is retreating, the beach width is maintained from sand released naturally from dunes and other sand reservoirs.
Beach erosion is the loss of sandy beach width as reservoirs are depleted, sand transport is hindered, or sand reservoirs are impounded by man-made hardening structures like seawalls.
In general, soft approaches of coastal protection are favored over hard forms in light of site-specific considerations and sand transport processes. Soft forms of protection include the replenishment and placement of small quantities (less than 10,000 cubic yards) of beach quality sand at specific shoreline locations. Sand bags using coconut-fiber or other natural materials may also be considered at appropriate locations for temporary erosion control.
Hardening sandy shorelines using sand-filled, geotextile bags, seawalls, groins, boulders, revetments, and sheet pilings is strongly discouraged. These methods frequently impact negatively on adjacent properties, interrupt the littoral flow of sand, and hinders accretion and release transport mechanisms from sand reservoirs. As a consequence, Shoreline Setback Approvals may be granted for soft approaches to beach erosion, whereas a Shoreline Setback Variance is normally required in cases where the shoreline is to be hardened.
Negative Effects of Hard Erosion Protection
Although hard forms of erosion protection may be useful in preventing coastal erosion on retreating shorelines, the hardening may result in increased beach erosion and loss. Hardening increases wave reflection and impounds sand reserves.
Consequently, hardening does not resolve sand budget deficits and may create interruptions in sand transport processes. This can result in unanticipated and unwanted outcomes for property owners if the structure
|is not appropriate for the situation and/or if it is not properly designed and sited.
Recent articles on beach processes, successful beach restoration projects, a Beach Management Plan for Maui, and prescribed forms can be obtained from the Planning Department or online.