Seawalls and Bulkheads in Kailua: What the Law Says, and What Lanikai Proves

Hawaii's Legal Framework: Discouraged, Not Simply Permitted

Hawaii's Coastal Zone Management Act sets a shoreline setback line at 40 feet from the upper reaches of the highest high tide and, per state coastal-policy materials, applies what is described as a 'no tolerance' policy toward new shoreline armoring. Property owners can still apply to build a seawall, revetment, or similar hard structure, but the process is deliberately long and difficult -- requiring a formal environmental review, public hearings, and approval from the Department of Land and Natural Resources -- and state rules specify that no variance for a new shoreline-hardening structure will be granted unless the applicant demonstrates the structure is necessary to protect an existing legal structure or activity from damage, and that the structure or activity cannot reasonably be relocated outside the shoreline setback area instead.

Act 16 goes further, prohibiting new private shoreline-hardening structures -- including seawalls and revetments -- specifically at sites with sand beaches and at sites where such structures would interfere with existing recreational and near-shore water activities, which describes the great majority of Kailua's own shoreline. In practice, this means a Kailua-area buyer should not assume that erosion at a specific property can simply be solved by building a new seawall -- for most parcels with a sand beach in front of them, current Hawaii law makes that a difficult-to-impossible permitting path, not a routine construction project.

Why the Law Is Written This Way: Lanikai as the Textbook Case

Hawaii's seawall-skeptical policy isn't an abstract environmental preference -- it's a direct, documented response to what happened in places like Lanikai, part of the greater Kailua community. Beachfront owners there erected seawalls and sandbag revetments, largely in the 1980s, to fight chronic erosion, and the city later issued after-the-fact permits for many of them, per ProPublica's investigative reporting. Of more than 100 beachfront structures in Lanikai, only a handful lack some form of shoreline armoring today.

The documented result: roughly 4,000 feet of natural beach was lost at Lanikai (Ka'ōhao) between 1911 and 2015, with the beach at north Ka'ōhao specifically disappearing between 1975 and 1982, according to University of Hawaii Climate Resilience Collaborative research. The mechanism is well-established in coastal engineering and specifically documented for Oahu by USGS: a near-vertical seawall reflects wave energy back onto the beach immediately in front of it, rather than absorbing that energy the way a natural, gradually sloped shoreline does, which accelerates erosion of exactly the sand the wall was meant to protect -- eventually eliminating the beach fronting the structure entirely in many documented cases. USGS estimates Oahu has lost roughly 29% of its beaches island-wide to this kind of armoring-driven erosion, and Lanikai is one of the most frequently cited individual examples in that broader body of research.

What This Means If You're Considering a Seawall-Fronted Property

If a Lanikai or other Kailua-area property under consideration already has an existing seawall or revetment, ask directly: when was it built, was it permitted (including any after-the-fact permit), what is its current physical condition, and is there still a beach in front of it or has the beach been lost? These are meaningfully different situations -- a well-maintained, legally permitted older seawall fronting a beach that's already substantially eroded is a different asset, with different ongoing maintenance and liability considerations, than a newer or better-preserved shoreline. A structural engineer with specific Hawaii coastal-property experience, not a general home inspector, is the right professional to assess an existing seawall's condition and remaining service life.

Also confirm who is legally responsible for the seawall's maintenance and any future repair or replacement -- in Hawaii, shoreline-hardening structures on private property are generally the private owner's maintenance responsibility, and given the state's restrictive stance on new construction, repairing or extending an existing legally grandfathered structure may itself face permitting hurdles beyond what a routine home repair would.

If a Property Doesn't Have a Seawall and Faces Erosion

For a property without existing shoreline armoring that faces erosion risk, Hawaii's regulatory environment generally steers owners toward softer, non-structural responses -- managed retreat, dune restoration and vegetation, or in some public-beach contexts, sand nourishment programs -- rather than a new hard structure, given the difficulty of the variance process described above. This page does not state which specific soft-protection options, if any, are realistically available for a specific Kailua-area parcel, since that depends heavily on the exact shoreline configuration, adjacent structures, and current DLNR policy at the time of inquiry. A coastal engineer and DLNR's Office of Conservation and Coastal Lands are the right sources for a property-specific assessment.

The Bottom Line for a Buyer

Treat 'I'll just build a seawall if erosion becomes a problem' as an assumption Hawaii law makes genuinely difficult to act on, not a fallback plan available on demand. For a property already protected by an existing seawall, understand its permit status, condition, and maintenance obligations before buying. And treat Lanikai's documented beach loss as a real, sourced cautionary example specific to this exact community, not a hypothetical -- it's one of the most cited real-world illustrations, in the actual coastal-science literature, of why Hawaii's regulators wrote the current rules the way they did.