Novarly Parcel · Sea level
Sea-level rise is only half the number
Where the land is also sinking, the water gains on you twice. A coast with 3 mm/yr of sea-level rise on land sinking 2 mm/yr faces an effective 5 mm/yr — and along parts of the US Gulf and Atlantic coasts, the land-motion half is the bigger half. We combine the NOAA tide-gauge trend nearest your address with satellite-measured ground motion into one number no listing will ever show you.
The arithmetic, in one line
effective rise = local sea-level trend (NOAA gauge) + local land sinking (satellite InSAR)
Both terms are long-term measurements. 5 mm/yr compounds to half a metre in a century — before any acceleration.
What is effective (relative) sea-level rise?
It is the rate at which the sea gains on the land at a specific place: the local sea-level trend measured by tide gauges PLUS any sinking of the land itself. A coast where the sea rises 3 mm a year over land sinking 2 mm a year faces about 5 mm a year of effective rise — nearly double what the sea-level number alone suggests.
Why does land sinking matter as much as sea rise?
Along much of the US Atlantic and Gulf coasts, vertical land motion is comparable to — sometimes larger than — the rate of sea-level rise itself. Groundwater withdrawal, sediment compaction, and the crust's ongoing adjustment since the last ice age all pull coastal land downward. Satellite InSAR now measures this to the millimetre for tens of millions of locations.
How do you calculate the combined number?
We take the long-term relative sea-level trend at the NOAA tide gauge nearest the address (over 500 gauges, many with 50+ year records) and add the worst satellite-measured downward land motion within 150 m of the address from peer-reviewed InSAR datasets. Both components are measurements, not projections.
Which US coasts have the highest effective rise?
The western Gulf of Mexico is the standout: gauges around Louisiana and Texas record some of the fastest relative sea-level rise in America, much of it from subsiding land. Parts of the mid-Atlantic — the Chesapeake region and Hampton Roads, Virginia — combine notable sinking with rising seas as well.
Can I check my own address?
Yes — the free checker screens any US address against satellite ground-motion data, and the full $19 report includes the combined sea-level exposure number for coastal addresses, alongside flood zone, shoreline change, wildfire, Superfund and dam context.
Sources: NOAA CO-OPS Sea Level Trends (public domain, attribution requested); Ohenhen et al. InSAR vertical land motion datasets (CC0/CC-BY); contains modified Copernicus Sentinel-1 data. Screening context — not a flood forecast or an engineering assessment. Updated 2026-07-23.
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