About 70% of Hawaii's sandy beaches are eroding. Here's what's happening, which beaches are most affected, and what it means for swimmers.
Hawaiʻi's beaches are disappearing. This isn't alarmism — it's the conclusion of multiple University of Hawaiʻi studies tracking beach widths over decades. Researchers have documented chronic erosion at beaches on all major islands, with some beaches losing several feet per year over extended periods.
The causes are interconnected: rising sea levels from climate change, the extensive hardening of Hawaii's coastlines with seawalls and revetments (which interfere with the natural movement of sand), reduced freshwater and sediment flow to the coast as streams have been altered, and the legacy of historical sand mining.
For swimmers and visitors, beach erosion has practical consequences beyond aesthetics: steeper beach profiles, changed wave patterns, different swimming conditions, and in some cases entirely different beaches than what was there 20 or 30 years ago.
Waikiki Beach is one of the most famous examples of managed beach erosion in the world. Almost all of Waikiki's sand is artificial — the original beach essentially disappeared by the early 20th century and was rebuilt and regularly replenished with imported sand. Without ongoing nourishment, much of Waikiki's beach would not exist today.
Kailua Beach has experienced significant chronic erosion, particularly at the southern end. Lanikai Beach, one of Oʻahu's most celebrated beaches, has lost substantial width and some sections front directly onto rocks with minimal sand during high tide. Koʻolina Lagoons are artificial — created by blasting lava and filling with imported sand.
Several Kaʻanapali resort beaches have experienced erosion, with seawalls constructed in front of hotels affecting natural sand transport. Kaʻanapali Beach near Black Rock has been affected by seawall construction. Kanaha Beach near Kahului Airport has seen changes. Maui's south shore has generally fared better due to more protected conditions.
Kauaʻi experiences some of the most dramatic seasonal beach changes in Hawaii. North shore beaches can lose enormous amounts of sand in winter swells, then rebuild in summer. This is partially natural, but sea level rise is beginning to prevent full seasonal recovery. Poʻipū Beach has been affected by erosion and storm events including Hurricane Iniki (1992). Hanalei Bay fluctuates significantly.
Magic Sands Beach (White Sands Beach) in Kailua-Kona demonstrates natural sand mobility in extreme form — its sand can literally disappear overnight during large swells, then return weeks later. This is partly natural but has become more frequent. Punāluʻu Black Sand Beach's black sand is naturally replenished by volcanic activity, but the beach has changed shape significantly. Hapūna Beach has maintained good sand levels due to its protected geometry.
Beach erosion isn't just a scenic problem — it has real implications for ocean safety:
As beaches erode, the sand face becomes steeper. This changes how waves break, intensifies backwash, and can create more powerful shore-break conditions even during moderate swell. An eroded beach that looks similar to before can behave very differently in the water.
When sand disappears (as at Magic Sands during large swells), the underlying lava is exposed. Entry and exit become significantly more difficult and injury risks increase. Falling on lava during shore break is far more dangerous than falling on sand.
Sand movement and erosion can alter the locations of rip currents. Rips that were in predictable locations may shift. This is particularly relevant at beaches with seawalls — the altered sand circulation creates different rip current patterns than existed before development.
Major erosion events disturb sediment and can temporarily increase turbidity. More significantly, when storms cause erosion, they also typically bring rainfall and runoff — meaning water quality and physical danger increase simultaneously. This is when the standard 72-hour post-storm rule applies most strongly.
Major storms cause both physical beach changes and water quality degradation simultaneously. After a significant storm, beach conditions may be dramatically different from what you expect — less sand, different wave patterns, and potentially active brown water advisories. Always assess current conditions after storm events.
Free alerts when water quality changes at your beach — especially important after major storm events.
No spam. Just safety alerts for your trip.
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with any government agency. Information about beach erosion is based on publicly available research but may not reflect the most current conditions. Beach profiles change over time and specific conditions should always be assessed on-site.
Always verify current water quality conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don't go out.