What "No Significant Trend" Actually Means

A measurement problem, not a null result

Every USGS transect has a measured rate AND a published confidence interval - a margin of error on that specific measurement. When the rate is smaller than its own confidence interval, the true trend could plausibly be zero, slightly eroding, or slightly growing; USGS's data simply can't tell which. Reporting a direction anyway would be false precision, so CoastErosionCheck reports "no significant trend" instead.

How common this actually is

Dauphin Island, AL is a typical example: across every segment this site covers, a majority show no significant trend rather than measurable erosion or growth - the ordinary case for the US coast, not an edge case, because most of the coast simply isn't moving fast enough for USGS's own survey precision to detect it.

Why this site doesn't hide it

A site that only reports confident-sounding numbers would either invent a direction for segments where none is reliable, or quietly drop them. Both misrepresent the coast. Every segment here gets a page regardless, and "no significant trend" is written as the calming, correct answer it is - not as a failed search.

When erosion IS worth acting on

Golden Meadow, LA shows what a genuinely significant rate looks like: a measured change large enough to clear its own confidence interval by a wide margin. See the methodology guide for exactly how that threshold is computed.

Where to go next

See the range this plays out across: Golden Meadow, LA, Dauphin Island, AL, Ocean Shores, WA.

Why USGS's Coastal Surveys Are a Different Age in Every Region · Why Some US Coastline Is Growing, Not Eroding