South Portland, ME Coastal Erosion Rate
Is the coast eroding 5.1 miles southeast of South Portland, ME?
The coast 5.1 miles southeast of South Portland, ME shows no statistically significant trend either way. USGS's transects measured a rate here, but it's smaller than the survey's own margin of error for this stretch, so calling it "eroding" or "growing" would overstate what the data actually shows.
The grain of this number
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest South Portland, ME into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 43.57°N, 70.23°W. USGS's New England / Mid-Atlantic assessment last surveyed this stretch through 2007-2009, computing the rate with its LRR method. Other US regions were surveyed in different years, sometimes decades apart, so this page states its own rather than implying one national vintage.
How solid is this number
This reading comes from 15 individual transects averaged together, 7% of which measured erosion rather than growth. USGS's confidence interval here is ±0.19 ft/yr. Taken at face value, this segment's raw 0.17 ft/yr reading would land it 903 of 1211 nationally - a number worth ignoring, since it's statistical noise rather than a real trend. Source: USGS Open-File Report 2010-1119. Rank 980 nationally for growth belongs to San Clemente, CA, 2616 miles from this stretch, measured at 0.34 ft/yr. 0.5 miles away, Portland, ME is the nearest other measured stretch: also no significant trend.
One address near South Portland: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.