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Erosion is a natural process along shorelines. It can occur over both the long and short term, as well as occasionally. Erosion’s main contributing factors are sea level rise, regional changes (i.e. loss of sediment), the shifting in the characteristics of waves and local adaptations and modifications (i.e. coastal structures).

Seawalls:

Seawalls are not as simple as they appear at first glance. Essentially a stone wall or pile of rocks, the physicality of them is not their complex component. The primary intention of the construction and design of a seawall is to ward off waves and prolong a specific shape and size of a shoreline. 

Policies and Conservation Efforts to Protect Beaches in Hawai’i Are  Failing
Video: University of Hawai’i News

Based on what can be observed throughout Hawai’i and many coastlines across the world, the question begs to be asked...

Are Seawalls Really Effective
  at Preserving Coastlines?

Their efficacy is extremely debatable as seawalls require staunch strategic planning and widespread impact assessment. 



Seawall, O’ahu

While at times successful in inhibiting sand removal along the length that the seawall stretches, erosion – specifically in areas that extend beyond the wall – is more often rapidly increased.



Beach Reenforcements, O’ahu 

Without proper and comprehensive planning, seawalls do little more than shift the erosion they are designed to prevent through the refraction, diffraction and reflection of waves into the first vulnerable and exposed location.

Representation of a Seawall Resulting in the Flanking of the Shoreline
Sketch: SAGE Journals

Shorelines and beaches are meant to ultimately shift landward.

Coastal structures – particularly seawalls, homes, roads and hotels in Hawai’i – impede the natural shifting and inundation of the land by wave action, prohibiting the perpetuation and creation of beaches in the future.

Scientists and environmentalists say seawalls are the predominant contributor to beach loss throughout all of Hawai’i.

The state is constitutionally required to preserve and protect beaches in Hawai’i as they are considered a public trust. Officials have neglected this responsibilty by granting easements and exemptions from protective laws, allowing more and more seawalls to be constructed. 



Attempts to Thwart Beach Erosion, Maui 

Environmetal Impacts

Recent estimations reflect that about 25% of the beaches on O’ahu, Maui and Kaua’i have already disappeared or suffered marked loss of sand directly due to seawalls over the last 100 years.  

Native species like the endangered Monk Seal and Green Sea Turtle have significantly fewer options for safe habitats to find rest and areas to lay eggs. 

By midcentury, the outlook is grim...

It is predicted that the number of healthy beaches will be drastically, dangerously and unbelievably be diminished to “just a handful.”

Pu’u Keka’a, Maui c. Then & Now

What Can Be Done?

Naupaka is a native plant to Hawai’i. The Naupaka shrub grows three to five feet with waxy, green leaves with whitish hair. The wax protects from sea spray and the hair protects from heat.

The flower is white with five petals all on one side. The seeds float and are salt resistant. Naupaka has a high tolerance to salt water – in fact, the seeds actually thrive in the sea. The root system is shallow and allows Naupaka to cling to rocks, shifting sand, and lava.



Naupaka

Naupaka’s berries and leaves are used as a famine food, while the bark aids in digestion and can be used for pegs in canoes.

In terms of shorline preservation...

The Naupaka plant can be used to prevent soil erosion and as a windbreak.