Ground subsidence in greater New Orleans
Space-geodetic measurements published in Nature documented subsidence in parts of greater New Orleans at rates that locally exceed 20 mm per year. The causes: compaction of young deltaic sediments, drainage of organic soils, and groundwater withdrawal. Subsidence is a major factor in the flood exposure of the region.
Source: Dixon et al. (2006), Nature
What is documented here
Greater New Orleans sits on young Mississippi Delta sediments that compact naturally — and faster where organic soils were drained, where fill was placed, and where groundwater is withdrawn. Satellite radar measurements published in Nature after Hurricane Katrina documented subsidence rates that locally exceed 20 millimeters per year in parts of the metropolitan area. The same study found that some of the areas that flooded worst had also sunk fastest.
New Orleans is distinctive because subsidence converts directly into flood exposure. Much of the city already sits below sea level, behind levees and drainage, so every additional millimeter of settlement is lost freeboard. Rates vary block by block with soil type, drainage history, and construction. Regional maps cannot tell you what a specific parcel, levee reach, or facility did.
For engineers and owners here, a site-specific movement history from the public Sentinel-1 archive is a cheap screening layer before a design, a purchase, or a dispute. It shows if the ground under a specific site sank steadily, accelerated, or held still — at screening grade, as an input to engineering judgment.
What the satellite archive holds here
The public Sentinel-1 radar archive, sampled at a representative point in this region. These numbers describe measurement availability — how often the satellites pass, and over what period — not ground movement. We compute movement per site, after the feasibility check.
- Radar acquisitions
- 117
- Revisit
- ~12 days
- Observed span
- 2022-01 → 2026-06
- Satellite tracks
- 1
Coverage stats as of 2026-07-14 · full Sentinel-1 archive extends back to 2015
What satellite radar can — and cannot — tell you
It can
- — Reconstruct a millimeter-scale movement history for stable radar reflectors (rooftops, pavement, rock, bare ground) on a specific site, from archive data
- — Show if the movement slows, stays steady, or accelerates — the trend shape that matters for decisions
- — Give you a dated record of what the ground did before a purchase, a design, or a dispute
It cannot
- — Measure surfaces that change between passes: dense vegetation, active construction, water
- — Replace geotechnical instrumentation, borings, or engineering judgment — it shows you where to look, not how to design
- — Tell you why the ground moves — it documents that it moves and how fast, as an input to the engineer who determines why
The honest economics: a commissioned InSAR study typically costs $10,000–30,000 and takes weeks. A self-serve report on one site costs $749, one time. The feasibility check before it is free — if the satellites cannot measure the site reliably, you pay nothing, and we say so.
Common questions
Is New Orleans sinking?
Parts of it, at very different rates. Published space-geodetic measurements documented subsidence that locally exceeds 20 mm per year in parts of the metropolitan area. The causes are compaction of young deltaic sediments, drained organic soils, and groundwater withdrawal. Other areas are comparatively stable — the variation is the point.
Why does subsidence matter more here than elsewhere?
Much of the region sits at or below sea level behind levees, so settlement converts directly into lost flood protection and drainage capacity. Differential settlement also distorts foundations, streets, and utilities built on soft soils.
Can I get movement history for one specific property?
Yes, at screening grade. Satellite radar interferometry can produce a movement time series for stable reflectors (rooftops, pavement, structures) on a specific site, from the public Sentinel-1 archive. First, the free feasibility check confirms that the satellites can measure the site reliably.
Check a site in the Louisiana region
Draw your site, and you get a free feasibility report from the Sentinel-1 radar archive in about one minute. It tells you how many passes cover the site, how often, over what period — and if the satellites can measure it at all. If they cannot, the report says so.
Check your site freeTelluric readings come from satellite radar and are screening-grade: use them to decide where to inspect. They do not replace geotechnical instrumentation or engineering judgment. Read the methodology.