As a group of engineers, scientists, planners and community representatives concerned with management of the Hawaiian shoreline, we note that severe erosion, such as on Oahu’s North Shore, has occurred before and is likely to occur again.

Erosion is caused by sand deficiencies related to human impacts, waves and wave-generated currents, and sea level rise. In fact, given that warming in the global climate system is unequivocal, the level of damage related to future erosion tied to sea level rise and increases in storminess is expected to grow. However, it is human impacts, such as seawall construction and coastal development on dunes, that contribute to the disappearance of our beaches.

Coastal erosion and shoreline retreat is a statewide problem. The state shoreline construction setback of 40 feet, adopted in the 1970s, was designed to provide a buffer from erosion. However, on Oahu, Maui and Kauai where chronic erosion and coastal retreat have been eating away at the majority of beaches and dunes for decades, this setback is no longer sufficient.

With our growing population and increasing development on our coasts, effectively managing erosion will require a variety of policies and tools:

» Maui and Kauai have implemented a shoreline setback that is scaled to the rate of erosion on individual lots. Higher rates of erosion lead to wider setbacks in order to accommodate future changes in the shoreline. Oahu has data that would allow the same sensible approach, and it is possible to implement such "erosion rate-based setbacks" on a statewide basis.

» Development has crowded our most iconic beaches and past decisions to protect threatened lands and roads have often caused beach narrowing and loss. However, there are federal, state and county programs to acquire private lands, purchase conservation easements, and otherwise incentivize the sending of development to more desirable areas. Enhanced efforts to shift development out of future erosion hazard zones could, over the next few decades, have a significant positive impact on public safety, ocean access and beach preservation for the benefit of future generations.

» Nourishing a beach and dune with sand can be an effective method of managing erosion, at least on a short-term basis. Beach nourishment in Hawaii is challenging, however, due to high costs, limited sand supplies and dangerous wave conditions. Nourishment is most effective when used with adequate setbacks, land purchases and other measures.

» There is a valid role for seawalls on our coastline, but armoring sandy beaches and dunes is a management tool with potentially negative impacts, and its use must be carefully considered and thoroughly evaluated. Seawalls can cause accelerated erosion on neighboring properties, often leading to the proliferation of armoring along the beach. Seawalls have been identified as a significant cause of beach and dune loss in Hawaii and should be avoided if possible.

» Coastal management has a scientific underpinning that provides improved understanding of why and where erosion strikes, the impacts of sea level rise, and how waves cause changes to beaches. Applied research programs at the university and at all levels of government need to be supported and enhanced as an integral component to coastal management.

Beaches are a fundamental element of our quality of life. Recent events have highlighted the need to review our system of coastal management and ask if it achieves the levels of public safety and environmental conservation that our beautiful and unique coastal system deserves.

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Co-authors of this article are Hawaii Shore and Beach Preservation Association board members Chip Fletcher (ex-officio), Jessica H. Podoski (ex-officio), Andrew Wycklendt, Chuck Blay, Matthew Barbee, Rob Walker, Dolan Eversole, Ruby Pap, Tara Owens and Greg Guannel.