If you read a daily newspaper or frequent a mainstream media website, then you've probably seen the Top 10 Beaches list that appears every year around Memorial Day, syndicated across the country. Hawai'i has had at least two beaches in the Top 10 each year for the past five years, and has topped the list 11 times since the rankings began in 1991. Professor Stephen Letterman of Florida International University has generated the list since its inception and updates it each year by rating America's 650 major public recreational beaches based upon 50 physical factors like water color, midday air temperature and number of sunny days. Given the criteria chosen to evaluate the best beaches, it's surprising that any beach outside Hawai'i could even crack the Top 10.
Why aren't more of Hawai'i's beaches on this list? Perhaps because many of Hawai'i's beaches, like Kahanamoku Beach in Waikiki (#3 on Dr. Beach's 2011 list) are slowly disappearing. Without frequent beach nourishment projects that harvest offshore sand to restore the beach, Kahanamoku Beach would not be one of the world's premier beach destinations. In fact, it might not even exist. Aside from Dr. Beach's list, maybe a better question to ask is why are Hawai'i's beautiful beaches“beaches that attract tourists from around the world, offer a multitude of social, cultural and recreational opportunities“disappearing?
Going, Going, Gone
Hawai'i's beaches are disappearing, or technically speaking, eroding, because of three primary reasons: sea-level rise, natural processes like swell events, currents, tsunamis, coastal storms and hurricanes, and human alteration. The first two causes are naturally occurring (well, on second thought, human activity is partly responsible for sea-level rise, too) while the third reason, human alteration, has resulted in dramatic beach loss across the Hawaiian Islands.
We may have no control over natural processes such as king tides, big waves or currents, but we do have control over the laws and policies that govern Hawai'i's coastline. One policy in particular, Hawai'i Revised Statute Chapter 205A-46, allows coastal landowners to protect their homes under conditions of "hardship." For instance, when the ocean shoreline encroaches to within 20 feet of a structure, property owners can be granted a variance that allows them to build a seawall to protect the property.
Research has demonstrated that rules allowing coastal landowners to build seawalls and other structures to protect their property have been disastrous for Hawai'i's precious sandy beaches. According to the University of Hawai'i coastal geologist Chip Fletcher, O'ahu has lost approximately 24 percent of its sandy beaches in just the past century. All of this lost sand adds up to 17 miles, and that's just on O'ahu. Even larger beach losses have been observed on the island of Maui. Dr. Fletcher's research has shown that nearly all of the beach loss on O'ahu has been attributed to shoreline armoring, or hardening of the shoreline. Other University of Hawai'i researches corroborated Dr. Fletcher's findings in 2010 and estimate that 40 percent of O'ahu's 112-mile coastline is armored, compared to just 25.6 percent in the 1970s.
Time Helps Us Forget
The use of historical data can help sharpen our attention when we're attempting to understand or document how the natural world has changed over time. Consider the following hypothetical situation: Suppose you asked two surfers, Gerry and Makana, how their local beach has changed. They both surf the same wave almost everyday, paddling out from the same stretch of sand, but Gerry has been surfing the spot since 1958, while Makana started surfing the same stretch of reef in 1993. Although both surfers will have historical perspectives and are commenting on the same beach, Gerry would provide a much different perspective on how their local beach has changed since he has 35 more years of experience to pull from than Makana.
The potentially different answers received from Gerry and Makana highlight what is known in fisheries management as the shifting baseline syndrome. Since Gerry and Makana started their surfing lives at the same beach during different time periods, their anchor, or baseline perspective is different. If you ask them what the beach used to look like when they first started surfing the break, Makana might say that the beach looks largely the same, while Gerry may reply that the beach used to be much wider with a greater abundance of marine life. As generations pass and the baseline shifts, the collective conscious accepts what they see now as normal. Had it not been for Gerry telling Makana about how wide the beach they paddle out from used to be, Makana would naturally accept that the tiny of pocket of sand he sees everyday is the way the beach has always looked.
Gerry and Makana's hypothetical perspective of their local beach is happening in reality on O'ahu and two famous beaches (or lack thereof) highlight this baseline shift. The North Shore's Waimea Bay has gone through drastic changes in recent decades, much like Diamond Head's tiny Kaluahole Beach. So why do we think of the Bay's Jump Rock and the waves splashing up against man-made stone walls fringing the Outrigger Canoe Club as just another day in paradise?
On wave-exposed beaches in Hawai'i, large ocean swells frequently bombard the coastline. These swells create powerful rip currents that pull sand away from the beach and carry it offshore, where it stays until changes in currents or waves return it back ashore. On an unaltered, natural beach, sand lost during the wave cycles is gradually returned to the shore and a dune system present behind the beach acts as a rainy day fund in case more sand is needed. As a result, a healthy, natural beach's profile doesn't really change. In other words, when a dune system is present behind a sandy beach, it is difficult to notice when the beach is naturally migrating landward. This natural process is known as coastal erosion.
The problem today is that the natural cycle of removal and renewal has stopped functioning in many places due to human alteration or development along the shoreline. Hardening shorelines with seawalls and other structures accelerates the loss of sandy beaches, causing beach erosion (much different from coastal erosion). Because the shoreline is not allowed to perform its natural landward migration during periods of sea levels rise and the dune system is not allowed to replenish the sand necessary to keep the beach profile the same, the result is a significantly narrowed beach, or one that may be lost altogether. To view the results of this firsthand, take a stroll on almost any O'ahu beach entirely fronted by seawalls, like the southeastern end of Lanikai Beach, anywhere along Kahala beach at high tide, or the dramatically altered Kaluahole Beach.
Kaluahole Beach is the small wedge of sand to the right of Makalei Beach Park on Diamond Head Road. Kaluahole Beach was once very different than it is today (our friend Gerry could tell us about it). According to John R. K. Clark, author of The Beaches of O'ahu and Hawai'i Place Names: Shores, Beaches, and Surf Sites, Kaluahole Beach was at one time the finest beach in that area until homeowners built groins and eventually seawalls to protect their homes, which were built too close to the ocean. As higher and higher seawalls were built, the sandy beaches fronting the seawalls disappeared, leaving only the small strip of sand that is there today. If you're a surfer and have ever surfed one of the many surf breaks in that area (Ricebowl, Tongg's, Suicides and Graveyards), imagine spending the day down at Kaluahole Beach, surfing and relaxing just as you would today at Kaimana Beach. Perhaps Kaluahole Beach would have made Dr. Beach's Top 10 list of America's best beaches, if not for the inclusion of unsightly seawalls. We'll never know.
A different story of human intervention and permanent beach alteration occurred decades ago at Waimea Bay on the North Shore. You're probably thinking, "Isn't Waimea one of the most beautiful, widest and pristine beaches on O'ahu?" Yes it is. But Waimea Bay has changed dramatically over the years and unless you were around the Bay in the 1940s and 1950s, you would never know the difference. Before sand mining operations removed over 200,000 tons of sand to fill beaches in Waikiki and elsewhere, there was so much sand in Waimea Bay that if you would have tried to jump off Pohaku Lele, Jump Rock, (the 20-foot tall rock jutting out of the water on the west side of the Bay) you would have jumped about six feet down into the sand below. Historical photographs are a testament to how much wider the beach used to be in the Bay.
Another threat to Hawai'i's beaches is sea level rise. Sea levels around the world rose from the last ice age until it leveled off around the 19th century. Since then, sea levels have slowly risen, until recently accelerating again in the early 1990s. Conservative estimates project the sea level around Hawai'i to rise by one meter (a little over three feet) or more by the end of this century. The impacts of a one-meter rise in sea level will be far-reaching and will require significant planning and adaptation. As you can imagine, sea level rise will speed up the effects of erosion on sandy beaches. Unless we begin a planned retreat from Hawai'i's coastline“especially in vulnerable coastal areas“Hawai'i could be faced with the proposition of seawalls fronting nearly every shoreline across the state.
SOS: Save Our Shore
There are many options available to deal with chronic erosion and sea level rise besides simply retreating from the coast. Adopting an anti-armoring policy could help ensure that the risk of future coastal development is absorbed by those choosing to build along the shoreline. When coastal landowners are allowed to protect their property at the expense of the public beach, the public trust loses a valuable social, cultural and recreational resource. This could be corrected by closing the Hawai'i Revised Statute Chapter 205A-46 loophole. Another available option that is continually used in Waikiki and extensively along the east coast of the mainland United States is beach nourishment. Beach nourishment can be a good temporary fix as long as a suitable sand resource is readily available, but costs will likely become increasingly prohibitive in the future.
An alternative solution that has been employed in Kaua'i and Maui Counties are variable erosion-based setbacks for new coastal construction projects. For large lots in Maui County (with an average lot depth greater than 160 feet), setbacks for coastal construction are determined by multiplying the rate of erosion by 50 years, and then adding another 20 feet of buffer area. The 20-foot buffer ensures that after 50 years, the shoreline doesn't reach or inundate the building. For similarly sized lots on Kaua'i, the building setback line is determined by multiplying the erosion rate by 70 and adding an additional 40 feet buffer.
Although the setback distances in both Maui and Kaua'i Counties are smaller for rebuilding existing properties and for lots with an average depth less than 100 feet, the new setback rules present reasoned and publicly palatable rules that will ensure that new development won't be impacted by erosion and sea level rise for at least the next half century. Hopefully by then we will have figured out how to slow the thermal expansion of the oceans and reverse the melting of alpine and polar ice caps. Ensuring that Hawai'i's beautiful beaches stick around for our keiki will be a challenge, but with more awareness, education and reasonable coastal planning, we can help ensure that future generations can enjoy the same beaches, just as we do today.