Under California Civil Code Section 830, if your land touches water, your property line ends at one of three places depending on what kind of water it is. Land bordering tidewater runs down to the ordinary high-water mark. Land bordering a navigable lake or stream without tides runs to the low-water mark. Land bordering any other water runs to the middle of the lake or stream. All three rules give way to whatever the original grant or deed actually says, so they operate as defaults rather than fixed lines.1California Legislative Information. California Code CIV 830 – Rights of Owners
Which rule applies to your parcel decides a lot: how much land you actually own, whether the state holds title to the ground beneath the water, what the public can do on the shore, and whether you can build anything at the water’s edge. The categories look simple in the statute, but each one carries its own measurement problem and its own set of public rights layered on top.
Tidewater: Ownership to the High-Water Mark
Coastal property stops at the ordinary high-water mark. Everything seaward of that line belongs to the State of California and is held for the public under the Public Trust Doctrine. The wet sand between high and low tide is public land, not part of your lot, even when your parcel description runs all the way to the beach.
The hard part is locating the line. The U.S. Supreme Court in Borax Consolidated v. City of Los Angeles defined the ordinary high-water mark for tidal boundaries as the mean high-tide line, calculated by averaging all high tides over an 18.6-year tidal cycle. One storm surge does not move the boundary; the average smooths those extremes out across nearly two decades of tide readings.2Cornell Law – Legal Information Institute. Borax Consolidated, Limited, et al. v. City of Los Angeles
The Public Trust Doctrine that governs the seaward side protects tidelands and submerged lands for public benefit. Its core principle is that trust lands belong to the public and must be used to promote publicly beneficial connections to the water, including navigation, fishing, and recreation.3California Coastal Commission. The Public Trust Doctrine That is why a precise survey matters before anyone builds close to the shore. A fence or deck a few feet on the wrong side of the mean high-tide line sits on state land, not private land.
Navigable Lakes and Streams Without Tides
When your parcel borders a navigable freshwater lake or river not affected by tides, the boundary sits further out. You own down to the low-water mark, so the exposed bank during drier seasons belongs to you. The state owns the bed below that point, which keeps public rights of navigation and fishing intact on the water itself.
Freshwater owners end up with more land than coastal owners, but the strip between the high-water and low-water marks can still carry a public trust easement. Holding title to that ground is not the same as having exclusive control of it.
What Counts as Navigable
Whether a waterway is navigable is a legal conclusion, not a question of whether a boat can float on it today. The federal test, which controls state title to submerged lands, asks whether the waterway was susceptible to use for commercial navigation when California became a state in 1850. Actual commercial traffic at that date does not have to be proven; capability is enough.4California State Lands Commission. A Legal Guide to the Public’s Rights to Access and Use California’s Navigable Waters
California also applies a broader state-law definition rooted in the public right of navigation. A stream or lake that fails the federal commercial-use test can still be treated as navigable under state law if the public has historically used it for recreation or travel. The classification is decisive: navigable status pushes your line back to the low-water mark and leaves the bed with the state, while non-navigable status gives you title all the way to the center.
Non-Navigable Waters: Ownership to the Center
Ponds, small creeks, and non-navigable streams follow the most generous rule for private owners. Your property extends to the middle of the waterway, a concept known as the filum aquae doctrine. Two neighbors on opposite sides of a small creek each own the streambed up to the center line.
The state does not claim the ground under non-navigable water, so you have more control over the bed and the surrounding land than owners on navigable waterways do. Disputes between neighbors over exactly where the center falls are common enough that a professional land survey is often the only way to resolve them. Waterfront surveys can run from a few hundred dollars to well over $10,000 depending on the terrain and the length of the boundary.
One boundary point worth flagging: owning the streambed does not carry with it an unlimited right to use the water. California’s Constitution requires that all water be put to reasonable and beneficial use, and diversions for irrigation or other purposes are governed separately under the Water Code.5Justia. California Constitution Article X – Water – Section 4 Where your title ends and what you can pump out of the stream are two different questions.
How the Boundary Moves Over Time
Water does not stay put, and neither do the lines it draws. California law splits changes into two categories with opposite results.
Gradual change moves the boundary with the water. When soil is deposited slowly through natural forces, the process is called accretion, and the upland owner gains title to the new ground as the shoreline builds out. The same principle applies to reliction, the gradual permanent retreat of water. Seasonal ups and downs do not count; the water has to recede for good.
Sudden change does not move the line. When a flood, earthquake, or other violent event rapidly reshapes a shoreline, the event is called avulsion, and the boundary stays where it was before the event. A storm that carves away a bank overnight, or dumps a bar of sediment in a single event, does not shift the legal line. That distinction protects both the state and private owners from losing title in an unpredictable natural disaster.
There is one wrinkle for anyone thinking about building out. When accretion is caused by artificial structures like jetties or seawalls rather than natural forces, the boundary is fixed at the ordinary high-water mark as it existed when the artificial influence was introduced. You do not gain title to land created by your own construction.6Cornell Law – Legal Information Institute. State of California, ex rel. State Lands Commission v. United States
Public Access Rights That Apply Regardless of Your Line
Even where you clearly own the ground, the public keeps significant rights along California waterways. The state Constitution bars any private landowner claiming frontage on a harbor, bay, estuary, or other navigable water from blocking access to the water when a public purpose requires it, or from obstructing free navigation.5Justia. California Constitution Article X – Water – Section 4
The California State Lands Commission administers these public trust rights, which have expanded through court decisions beyond commerce, navigation, and fishing to include swimming, boating, general recreational use, and preservation of land in its natural state.7California State Lands Commission. Public Trust In practice, even where you own to the water’s edge, you generally cannot wall the public off from reaching navigable water across your land if no alternative route exists.
When the Deed Overrides Section 830
All three rules in Section 830 apply only if the grant that created the property does not say otherwise. If a deed, patent, or historic land grant sets the boundary at a specific landmark, coordinate, or fixed line rather than following the water, that language controls.
This is not a rare situation. Many California parcels trace back to Mexican land grants, railroad patents, or early statehood-era deeds that used geographic features rather than the water line. A deed calling for a boundary at a particular ridge or fence holds even if the water has since moved. The only reliable way to know whether your property follows the default water-mark rules or a historical exception is to read the original grant deed and title policy, ideally with a real estate attorney familiar with California waterfront titles. Restrictive language buried in an old grant can shrink or extend what Section 830 would otherwise give you.