ROYAL HAWAIIAN BEACH, WAIKĪKĪ - A RESULT OF HUMAN INFLUENCE AND INTERVENTIONChristopher Conger and Dolan Eversole, University of Hawai‘i Sea Grant College Program

Publication of this report was funded in part by a grant/cooperative agreement from NOAA, which is sponsored by the University of Hawai‘i Sea Grant College Program, School of Ocean and Earth Science and Technology

(SOEST), under Institutional Grant Number NA09OAR4170060 from the NOAA Office of Sea Grant, Department of Commerce. The views expressed herein are those of the authors and do not necessarily reflect the

views of NOAA or any of its sub-agencies.

UNIHI-SEAGRANT-TT-11-01

EXECUTIVE SUMMARYConcerns related to coastal development in Waikīkī have centered on the possible impact on the active beach system. It is important to first recognize that the entire region of Waikīkī can be characterized as having a man-made coastline, including much of its current beach. To understand the changes that have occurred along sections of Waikīkī’s coastline, it is necessary to delve into both the coastal science and history of the area. Scientists, engineers, and local residents have observed and documented both the human-induced and natural factors that control sediment distribution in the region. These data have made it possible to create basic models for sediment transportation patterns in Waikīkī. Understanding the well-documented history of human impacts along this coastline helps to explain many of the beach and shoreline changes that have occurred over the past century and ultimately will assist the community, coastal resource managers, and local decision-makers in understanding the nature of cause and effect for this critical beach resource.

The beach along Waikīkī’s coastline is narrow for several reasons:

• The natural, historical shoreline in Waikīkī had intermittent and narrow sandy beaches. Maintaining the wider beaches for which Waikīkī has become famous for has and will require ongoing work and an agreed upon plan.

• Waikīkī is an urban beach with shoreline structures such as groins, which extend seaward from the beach, and seawalls, which currently define the mauka extent of the active beach system (Figure 1). These hard structures dominate Waikīkī ’s beach dynamics by exerting control on sediment transportation and placement, defining where beaches will be located and how wide they will be. During high tides, waves and currents have maximum interaction with these groins and seawalls.

• Historical sand hauling from the beach and dredging/mining of the reef in Waikīkī during the early 20th century significantly reduced beach volume and changed the nearshore morphology.

• Expansion of the Kühiö Beach Basin and improvements to its exterior walls have helped to contain sand within the basin. Prior to these improvements, significant amounts of imported sand had been lost to the nearshore waters and adjacent beaches.

Figure 1. Aerial view of the Waikïkï-Royal Hawaiian and Kühiö Beach systems.

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All of these effects have contributed to the slow, chronic erosion along this portion of the Waikīkī shoreline, resulting in a trend toward beach narrowing.

If the long-term goal for the area is to maintain a wider beach, then there are two possible scenarios:

1) Bring in additional sand to increase the beach volume. Increasing sand volume has been an effective strategy for mitigating beach narrowing, both in Waikīkī and in other coastal areas in the U.S. In areas such as Waikīkī, where significant volumes of sand have been brought into the system from external sources, use of beach quality sand that is located offshore of narrowing beaches can minimize environmental impacts. In Waikīkī, it may uncover the skeletons of previously thriving coral reefs that were covered by imported sand, and allow the natural resettlement of coral larvae to restore coral reefs.

2) Remove the seawalls and allow the beach to migrate inland. Removal of the adjacent, high-density development and supporting infrastructure, such as roads, water, sewage, power, and telecommunication lines will also be necessary. Other states have pursued this course of action, but usually in low-density communities where land swaps or willing-seller land sales were affordable to state government. This approach is widely thought to be both impractical and economically untenable in Waikīkī due to the potential dramatic impact to major development and infrastructure (Figure 2). The removal of these existing shoreline structures would likely lead to a more landward position of the beach but not necessarily result in a wider or healthier beach system without additional sand inputs. In addition, the removal of existing shoreline structure would likely result in increasing the vulnerability of coastal development and infrastructure to low to moderate coastal hazards (not extreme major events) such as storm inundation, erosion, and sea-level rise.

Figure 2. Waikïkï-Royal Hawaiian Beach illustrating the extensive shoreline development.

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BACKGROUNDRecent discussion of current and planned resort developments in Waikīkī has included questions regarding their potential impact to Waikīkī’s beach resources. Considering the social and environmental value of Waikīkī Beach, combined with its direct contribution of $2 billion per year in visitor expenditures1 for the state, these are very relevant questions. Development concerns in Waikīkī need to reflect the limitations and actual physical constraints on its beaches. In natural settings, a beach will continually evolve, delicately balancing its shape and location with the conditions of the ocean. However, urban, engineered beaches like Waikīkī often have a decidedly different evolution dominated by coastal engineering features like seawalls, groins, beach nourishment, and sand mining and deposition. In order to best protect and manage the sandy beach resources in Waikīkī, it is important to fully understand the net effect of the shoreline structures, human activities, and coastal processes that control the movement of sand in the shoreline system.

In 2002, the University of Hawai‘i identified seven different littoral cells during a detailed coastal study2 of Waikīkī Beach. A littoral cell is typically an enclosed sediment environment where the dry and nearshore sands behave as a single system along a finite length of coastline. Each of these cells is generally independent of the others, though they may share sand from time to time. The “health,” or general condition, of the beach in each of these cells is a reflection of the volume of sand available to the beach and the space available for the beach to migrate with changing ocean conditions. These two factors control how healthy Waikīkī Beach looks and behaves in any given cell.

For the purposes of this discussion and lack of a commonly accepted place name, we refer to the beach system that extends from the Royal Hawaiian Groin at the west end to the Ewa Kühiö Basin at the east end as the Royal Hawaiian Beach. The dominant controls throughout Waikīkī’s urban history have been seawalls, groins, and beach sand placement (and removal). Waikīkī’s seawalls have drawn both a figurative and literal line in the sand, disconnecting the direct effects of mauka development from the dynamic processes that shape the beach system, while also creating barriers preventing mauka movement of the beach3. Moreover, groins and other shoreline structures that protrude seaward from the shoreline, both current and historic, have strongly influenced how the sand moves along the Royal Hawaiian Beach, interrupting currents and causing beach growth or loss depending on the location of the structure. Beach nourishment and mining have been the dominant factors controlling beach volume, or available sand, for all of Waikīkī’s beaches. From a coastal process perspective, it is these seaward shoreline structures, the groins and seawalls, not the buildings landward of them that have dictated the beach morphology in Waikīkī for over 100 years and continue to do so today (Figure 3).

1 Waikïkï Improvement Association, Economic Impact Analysis of the Potential Erosion of Waikïkï Beach, Final Report, September 3, 2008.

2 Miller, Tara L., and Fletcher, Charles A., November 2002. A Report Prepared for the State of Hawai‘i, Department of Land and Natural Resources, Land Division.

3 For case studies on seawall impacts to sediment dynamics in Hawai‘i and along other coastlines in the United States, see: Shipman, H., Dethier, M.N., Gelfenbaum, G., Fresh, K.L., and Dinicola, R.S., eds., 2010, PugetSound Shorelines and the Impacts of Armoring—Proceedings of a State of the ScienceWorkshop, May 2009: U.S. Geological Survey Scientific Investigations Report 2010–5254, 262p.

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ENGINEERING HISTORY AND NATURAL CONTROLS FOR THE BEACHFor Royal Hawaiian Beach, history clearly shows the influence of man along the coast. According to a comprehensive review4 on the history of Waikīkī Beach completed by the University of California, Berkeley, the Royal Hawaiian Beach was a low, sandy beach in 1865 and was partially vegetated and backed by a grove of coconut trees. Between 1906-1910 a small groin was built in the middle of this beach. By 1910, there were news stories documenting the concern of local citizens about the detrimental impact of the extensive sand mining activities along this coast. At that time, there was a narrow beach, often bisected by the ‘Äpuakehau Stream, and heavily impacted by run-off from upland rain events. The relict ‘Äpuakehau Stream channel can still be seen as a sand filled depression in the reef, often used by catamarans on their daily runs to and from the beach.

By around 1927, the small groin in the middle of the cell had been removed and the long, curved, submerged groin fronting the Royal Hawaiian had been built. While removal of the small groin stabilized the middle portion of the Royal Hawaiian Beach, the long, curved groin5 on the western end had significantly widened the west end of the beach. Similar to most groins, the beach on one side grew at the cost of the beach on the other side. Thus, at the same time that the west end of Royal Hawaiian Beach was growing, the beach on the other side of the groin was shrinking. This structure was redesigned around 1930, more than doubling its length and increasing the height near shore, making it even more effective at accumulating sand on the west end of the beach. By this time, all seawalls along the mauka side of the beach had been constructed.

4 Wiegel, Robert. L., November 15, 2002. Waikïkï, O‘ahu, Hawai‘i, An Urban Beach, Its History From a Coastal Engineering Perspective.

5 This curved groin still present on the beach today between the Royal Hawaiian and Sheraton Waikïkï properties and is partially submerged and extends landward connecting to the Royal Hawaiian seawall.

Figure 3. Waikïkï-Royal Hawaiian and Kühiö Beach illustrating the extensive shoreline structures.

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Figure 4. Image modified from the University of Hawai‘i Coastal Geology Group 2002 report, showing dominant sediment longshore transport pathways in yellow and red arrows and the variety of structures that extend into the ocean.

There were no major changes to the structures controlling this beach during the years between 1930-1970, though development mauka of the seawalls continued. During these decades the beach grew and shrank, disappearing in locations for years at a time, while the beach was pinched against the mauka seawalls and confined by the long curved groin on the west end. This same period of time saw the original construction of the Kühiö Basin and several major sand nourishment efforts within it. These beach fill efforts within Kühiö Basin leaked sand to adjacent beaches and the reef, likely adding considerable volume to Royal Hawaiian Beach over the years.

In 1972, there was another major beach restoration effort at Kühiö Beach, which brought additional sand volume into Royal Hawaiian Beach. Some of the sand added within the basin began escaping into this cell and rapidly increased beach volumes from 1972 until 1975, when the Kühiö Basin’s walls were rebuilt. Since 1975 the Kühiö Basin no longer provides a long-term, gradual supply of sand, and the trend for Royal Hawaiian Beach, has settled into chronic, slow erosion that moves sand offshore from the dry beach as it is pinched against the seawalls.

The health of Royal Hawaiian Beach, from 1975 to today is a much better model of the natural factors that are influencing the cell. Kona events during the winter months move sand from the west end of the beach toward the middle, and summer swell pushes it back again. During large wave events a strong offshore rip current pulls sand out of the ‘Äpuakehau Stream Channel. Once the sand moves far enough offshore and into deeper water it becomes unavailable, as waves and currents will no longer be able to return the sand to the beach. The long-term trends are slow erosion and continued migration of sand from the east to the west along Royal Hawaiian Beach. Though the beach is constantly responding to the natural factors and evolving, it is limited within the confines of the historic seawalls and groins.

Without changing the shoreline structures, the only other way to affect the health of Royal Hawaiian Beach is by adjusting its sand volume. Throughout the modern, urban history of Royal Hawaiian Beach, there have been no documented direct additions of beach sand, though much has leaked in from adjacent beaches. The first planned effort will be a state beach nourishment project that is scheduled to begin in the winter of 2011. The project is expected to add 24,000

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CONCLUSIONBoth coastal science and the history of Waikīkī show that when an effective seawall acts as a barrier between the littoral cell (beach sand system) and landward development, it is the seawall that interferes with coastal processes, not the development behind it. One can argue that in Waikīkī, a “line was drawn in the sand” at the turn of the 20th century when these original seawalls were built. In this respect, any potential impact to the active beach system from the seawalls was done long ago. It is likely that the current beach has reached a dynamic equilibrium with the shoreline structures and historic volume changes. If history and science bear true, then this beach’s health, or its ability to respond to changes in its local ocean environment, will not be directly impacted by activities occurring landward of these shoreline structures. That said, the ad hoc nature and uncoordinated history of beach structures in Waikīkī highlight the need for a comprehensive beach management plan. Such a plan would include a cost versus benefit assessment of the impacts of beach loss and beach nourishment along with potential environmental, hazard, social-cultural, climate and funding options and constraints. This is especially important when considering the possible impacts to the beach from the continuation of locally rising sea levels.

cubic yards of sand to the beach, returning the beach volume and shape to approximately what is was in 1985. This sand will not be trucked in from outside sources, but instead will be pumped from offshore sand fields that have been filled in by the natural processes that remove sand from Royal Hawaiian Beach.

The piecemeal history of shoreline structures and sand mining and nourishment in Waikīkī illustrates the need for a comprehensive long-term beach management plan for the area, particularly in the context of coastal hazards and climate change. An agreed upon beach management plan would outline the goals for future beach management activities and help to ensure that planned beach projects along all of the Waikīkī coastline worked in conjunction, to the maximum extent possible. A well-articulated beach management plan can improve coastal natural hazard resilience while also reducing overall expenditures, both of time and money.

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1927

2005

1992

1985

1968

1959

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Historic Aerial Photographs of Waikīkī Beach

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