Policies to conserve and enhance beaches, public access, and coastal open space are failing in Hawaiʻi according to a recently published study by researchers at the University of Hawaiʻi at Mānoa.

A team of specalists in coastal erosion, sea level rise, and urban planning quantified land use on a section of Oʻahu, Hawaiʻi coast over the period 1928–2015, a time of slowly rising sea level. They concluded that coastal zone management practices in the state, and nationally, will require new policies, or more effective ways for implementing existing policies, in a future characterized by accelerating sea level rise.

U.S. coastal zone management (CZM) relies on an integrated chain of federal to local programs that emphasize beach conservation, public shoreline access, and preservation of open space, as well as other goals. In testing the efficacy of these policies over a century of slow sea level rise, the team found a shift from accreting shorelines and wide beaches in the early data, to expanding erosion and beach loss concurrent with increasing backshore development and seawall construction throughout the period of study—trends at odds with policy objectives.

“The purpose of our study is not to point fingers at Hawaiʻi’s coastal zone managers. We donʻt want to be hard on the people. We want to be hard on the problem. The state’s political leaders, CZM managers, and stakeholders should use the information in this study to update policies so that beach conservation is achieved, and to develop sea level rise adaptation strategies,” said Chip Fletcher, associate dean and professor of earth sciences at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST) and senior author on the study.

The Hawaiʻi Coastal Zone Management Program (HCZMP), a typical federal-local partnership, was established in 1977 to “provide for the effective management, beneficial use, protection, and development of the coastal zone.” The HCZMP regulates the coastal zone through state and local agencies.

As a state, Hawaiʻi relies heavily on beaches for economic, environmental, and cultural purposes. Rare and endangered species such as the Hawaiian Green Sea Turtle, the Hawaiian Monk Seal, and myriad shorebirds rely on beaches as critical habitat.

“With tourism being Hawaiʻi’s main industry, and beaches providing life-long memories for nearly every child and family, it is perplexing that authority figures have not implemented more effective policies and regulations to ensure beach conservation,” said Alisha Summers, lead author of the study who was an undergraduate student at SOEST while conducting this work.

Using a sequence of aerial photomosaics dating from 1928 to 2015, the team created geographic information system datasets to document a detailed history of shoreline change and coastal development over the past century. A number of features were analyzed including beach erosion and accretion, shoreline hardening, coastal development, flanking, and wave and weather events.

As development of beachfront lots increased, so too did the construction of seawalls

The ocean right up against a rock sea wall

Beach loss fronting armored shorelines are a common sight. Photo: Alisha Summers

“Shoreline hardening increased from a complete absence of seawalls in 1928 to nearly 5 km of hardened shoreline today,” said Brad Romine, coastal management specialist with Hawaiʻi Sea Grant and co-author of the study.

“This century-long pattern of shoreline hardening and beach degradation seemed to escape notice until the research caught up in the last couple decades. Tracking cumulative impacts, as is required with the current environmental review process, must be a key part of the management doctrine in this case.”

The detailed history clearly shows several other trends and relationships over the 87 years of the study period.

Net shoreline change shifted from accreting to erosional on 74 percent of the coast, with more than 45 percent of this shift due to flanking, that is, erosion triggered by nearby hardening.

Data confirm the existence of a “hardening domino effect” in which the first seawall triggers a succession of seawalls by adjacent property owners as the hardened shoreline initiates and accelerates erosion on adjacent, once stable beaches.

Ultimately, nearly 20 percent of beach length has been lost, and 55 percent of beaches have narrowed

Damaged homes on the shoreline

Extensive shoreline erosion near homes at Mokulēiʻa on Oʻahu’s north shore. Credit: Brad Romine.

“Despite the adoption of a policy to preserve coastal ecosystems and environments, Hawaiʻi’s beaches continue to narrow and disappear while seawalls and revetments continue to be built,” said Daniele Spirandelli, assistant professor in the UH Mānoa Department of Urban and Regional Planning and extension faculty in Hawaiʻi Sea Grant.

“The data published in our new study are representative of state-wide and nationwide patterns of permitted coastal environmental destruction by shoreline hardening,” said Fletcher. “Rather than proving effective at achieving the stated goals of conserving the natural coastal system, ‘hardship variances’ embedded in these same policies allow shorefront owners threatened by erosion to build seawalls and other forms of shoreline hardening to protect upland development. This development includes private homes and property, public roads and parks, and federal lands such as military installations. Hardship variances undercut the very purpose of CZM conservation policies.”

“Why have we allowed the destruction of our beaches? I think there are multiple factors including legal loopholes such as the hardship variance. Other factors include a lack of strict enforcement, a misplaced emphasis on ‘balanced management,’ a legal bias toward private property rights and the simple fact that denying a homeowner a seawall permit may mean the destruction of their house,” said Fletcher. “Whatever the reason, it is time to develop an exit strategy, because living on a beach in a time of sea level rise acceleration puts lives, property and communities at risk.”

“If authorities intend to protect existing beaches for future generations, they must implement policies that allow beaches to migrate landward with rising seas,” said Fletcher.

The logic is simple: in an era of sea level rise, shorelines must migrate landward if they are to function as healthy ecosystems. Sea level rose more than 400 feet since the last ice age and beaches persist.

“Coastal systems are not intrinsically threatened by sea level rise provided they can freely migrate landward. However, seawalls prevent beach migration and will lead to their extinction unless we change how we manage our shoreline. Clearly, if we want beaches for our children and their children, we must get out of the way of migrating shorelines.”

Questions and Answers

1. What did you discover?

U.S. coastal zone management policy relies on an integrated chain of federal to local programs that emphasize beach conservation, public shoreline access, and preservation of open space. We test the efficacy of these policies over a century of slow sea level rise by quantifying land use on a section of Oʻahu coast 1928-2015.

We found a shift from accreting shorelines and wide beaches in the early data, to expanding erosion and beach loss concurrent with increasing backshore development and seawall construction throughout the period of study; trends at odds with policy objectives.

We conclude that failure to achieve conservation policy goals under slow, historic sea level rise (1.2 to 1.4 mm/yr) implies that preserving beaches, open space, and public shoreline access will require new policies, or more effective ways for implementing existing policies, in a future characterized by accelerating sea level rise.

2. What are the main findings of the study?

1. The term “shoreline protection” can have multiple and opposite meanings. To consultants hired by upland owners it typically means shoreline hardening with a seawall or revetment. To coastal managers and scientists it means environmental conservation.

2. The rise of buildings on beachfront lots and subsequent use of seawalls are strongly correlated. In 1928, 39 beachfront buildings existed without need for hardening. From 1928 to 1975 beachfront buildings increased more than fourfold, from 39 to 177, and the length of hardened shoreline increased to 45 percent. By 2015, 189 beachfront buildings fronted 63 percent of the shoreline.

3. Over the 87 years of the study period (1928–2015) the following trends and relationships were found: shoreline hardening increased 63 percent; net shoreline change shifted from accreting to erosional on 74 percent of the coast; more than 45 percent of this shift was due to flanking (erosion triggered by nearby hardening); today, nearly 20 percent of beach length has been lost; 55 percent of beaches have narrowed.

4. Prior to creation of the Hawaiʻi Coastal Zone Management Program in 1977, 0.8 percent of beaches had been permanently lost. Since then, 19 percent of beaches have been lost.

5. Coastal Zone Management policies appear to have done little to prevent a 29 percent increase in coastal hardening that occurred between 1975 and 2006. Data shows this spike in hardening followed the build-out of 78 percent of shoreline lots by 1975, and was concurrent with an expansion in average building area that occurred between the 1970’s and 2015.

6. Erosion rates on more than 27 percent of the study area significantly accelerated due to flanking. Often, rates shifted from accreting to erosional following hardening on the adjacent shore. Data confirm the existence of a “hardening domino effect” in which the first seawall triggers a succession of seawalls by adjacent property owners—promoting decades of coastal hardening that sentence an entire length of sandy beach to narrowing and eventual loss. Roughly 45 percent of observed hardening was in response to adjacent seawall or revetment construction. Continued construction of beachfront buildings throughout the period contributed to this effect. Buildings initially arose on stable shorelines, but became vulnerable to erosion due to flanking.

7. Coastal development in Hawaiʻi is regulated through three main policies: 1) Local (county) zoning ordinances that establish approved uses, 2) Special Management Areas (shoreline areas with special controls on development), and 3) Shoreline Setbacks. Ten objectives are identified in the authorizing statute for the Hawaiʻi Coastal Zone Management Program (HRS §§ 205A), summarized here as protecting and improving natural resources and ecosystems, reducing exposure to hazards, providing for public participation, affording economic activity in suitable locations, and beach protection for public use and recreation. Each objective is further expanded with an accompanying policy. The Beach Protection policy has three elements: (1) locating new structures inland, (2) prohibiting private erosion-protection structures, and (3) minimizing public erosion protection structures.

8. In spite of substantial legal authority to protect beaches, appointed and elected land use officials have frequently approved hardship variances allowing seawall construction; permitted expansion of single family homes within the Special Management Areas; approved building on coastal lots without regard to shoreline stability; and allowed maintenance and expansion of non-conforming buildings.

3. What are the reasons for the failure to achieve policy objectives?

We find a clear failure to achieve policy objectives for six primary reasons:

  • The implementation of a fixed distance setback law allowed building and road construction without regard to coastal erosion patterns, thus ensuring that at least some development will be threatened by erosion before its planned lifetime;
  • The application of Special Management Areas rules has allowed expansion of building footprints associated with single-family homes; this ensures that most buildings will have no effective lifetime as they may be continuously renovated, even expanded, further locking in eventual threats by erosion;
  • The setback law contains a loophole called a “hardship variance” allowing all forms of development to be protected by coastal hardening, ensuring the demise of beaches by preventing their migration (a physical certainty in a regime of long-term sea level rise).
  • This sequence of permissive development, hardening, and beach loss is further promoted by the flanking process, whereby a hardened shoreline triggers and accelerates erosion on an adjacent beach.
  • The shoreline is managed parcel by parcel. This promotes short-sighted decision-making without awareness of accumulated impacts, long-term trends, or place-based characteristics.
  • Agency personnel with authority to decide on applications for coastal zone uses are not required to, and traditionally have not had, scientific training in the interpretation of potential impacts. In lieu of this, decisions are made on the basis of statements from consultants hired by the applicant—a situation that is ripe for conflict of interest.

4. How was this study conducted?

We documented a detailed history of shoreline change and coastal development over the past century. We utilized a sequence of orthorectified vertical aerial photomosaics dating from 1928 to 2015 to create geographic information system datasets.

A number of features were quantified and analyzed: beach erosion and accretion, shoreline hardening, coastal development, flanking, and wave and weather events. Data were categorized in terms of the coastal geomorphology and as time period averages.

5. What are the implications of these findings?

Congress enacted the U.S. Coastal Zone Management Act in 1972 to “preserve, protect, develop, and where possible, to restore or enhance the resources of the nation’s coastal zone.” The Hawaiʻi Coastal Zone Management Program (HCZMP), a typical federal-local partnership, was established in 1977 to “provide for the effective management, beneficial use, protection, and development of the coastal zone.”

HCZMP regulates the coastal zone through state and local agencies. In fiscal year 2016, for instance, the National Oceanic and Atmospheric Administration, Office for Coastal Management allocated more than $2 million among Hawaiʻi agencies in support of coastal management activities aligned with federal and state program goals.

The data published here are representative of state-wide and nationwide patterns of permitted coastal environmental destruction by shoreline hardening. Rather than proving effective at achieving stated goals of conserving the natural coastal system, “hardship variances” embedded in these same policies allow shorefront owners threatened by erosion to build seawalls and other forms of shoreline hardening to protect upland development. This development includes private homes and property, public roads and parks, and federal lands such as military installations. Hardship variances undercut the very purpose of Coastal Zone Management conservation policies.

6. Why do these findings matter to the State of Hawai‘i?

Despite the adoption of a policy to protect the shoreline, Hawaiian beaches continue to erode while seawalls and revetments continue to be permitted. If authorities intend to protect existing beaches for future generations, they must implement policies that allow beaches to migrate landward with rising seas.

As a state, Hawaiʻi relies heavily on beaches for economic, environmental, and cultural purposes. Rare and endangered species such as the Hawaiian Green Sea Turtle, the Hawaiian Monk Seal, and myriad shorebirds rely on beaches as critical habitat. The children of Hawaii learn ocean safety, how to read the signs of nature, and accumulate family memories on beaches.

The State’s political leaders, Coastal Zone Management managers, and stakeholders should use the information in this study to update policies so that beach conservation is achieved, and to develop sea level rise adaptation strategies.

7. Were these findings a surprise?

No. The issue of coastal erosion on Oʻahu is not new. The lack of effective enforcement and implementation of Hawaiʻi’s coastal policies has long been known. What was missing was the objective quantification of the problem published here.

8. Who funded this work?

This work is funded by the following: H.K.L. Castle Foundation, Hawaiʻi Department of Land and Natural Resources, Hawaiʻi Coastal Zone Management Program, and Honolulu Office of Climate Change, Sustainability, and Resiliency.