Blog · September 30, 2026
What Is Accretion along a River?
Accretion is the gradual, imperceptible addition of land by the deposit of soil along a water boundary. When the boundary is ambulatory, the owner may gain that slow addition. A sudden dump of fill is not accretion, and a tax map’s moving shoreline is not a conveyance.
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Slow deposits, not a weekend of dirt
Along many rivers and some shores, the boundary follows the water in a way the law describes as ambulatory. Soil that builds up gradually by natural deposit is accretion. The upland owner’s boundary can move with it. The classic companion word for the erosion that slowly eats the bank is erosion, and the owner can lose land that way too. The key is the pace and the cause. The change has to be gradual and, in the traditional phrase, imperceptible in its progress, even if you can see the result after many years. A flood that tears off an acre overnight is avulsion, which usually leaves the boundary where it was. A landowner who trucks in fill is making land by construction, not receiving accretion. Calling the fill accretion does not move the deed line to the new edge.
What the deed and the plat have to do with it
If the deed calls to the river, or to the ordinary high water, the boundary may be the kind that can accrete. If the deed calls to a fixed monument, a meander line that was intended as the boundary, or a distance that stops short of the water, the boundary may be fixed and accretion belongs to someone else or to the public. The meander line on a GLO plat is often not the boundary. The water is. That sentence has exceptions where the meander was grossly in error or the grant excluded the shore. You read the patent and the cases only with help. You do not read them by painting the GIS shoreline a new color. County GIS shorelines come from photography and hydrography layers. They are assessment graphics. Platbookmapper links to them and does not adjudicate accretion.
Leave the bank alone
Do not dump fill to manufacture accretion, do not fence a new bar because a photo shows it, and do not cross a neighbor’s bank to watch the channel. A surveyor can compare older surveys, the deed calls, and the present bank and tell you whether the question is even an ambulatory boundary. A lawyer can address title to the new ground. A phone GPS outline of a sandbar is not a survey. The sandbar may be public, may belong to the opposite owner if the thread moved, or may be accretion to you. Those are different outcomes. The photo cannot pick one.
What to do next
- Read whether the deed boundary is the water or a fixed line.
- Separate gradual deposit from sudden change and from imported fill.
- Do not fence a new bar from an aerial photo.
- Ask a surveyor and a title lawyer before you treat new ground as yours.
The mix-up to avoid
Calling any newer shoreline your property. Accretion is a slow natural process tied to an ambulatory call. A shifted aerial, a GIS edit, or a load of fill is a different event.
Questions people ask
Does accretion apply to a lake lot with a fixed seawall call?
If the boundary is the wall or a recorded line, the wall stays the line even if sand piles up beyond it. If the boundary is the water, the analysis changes. The call decides which article you are in.
Who owns an island that forms in the river?
That is a separate title question, often depending on where the island formed relative to the thread and on the grants. Do not assume an island in front of your lot is accretion to your bank. It may not touch your boundary at all.
Find the county map
Open Platbookmapper and pick the county that taxes the land. Use that viewer to get the parcel id, then match it to the recorded plat if you need the easements and lot numbers.
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey.