Flood maps flag contaminated private wells
After Hurricane Florence, 41.2% of tested wells had total coliform and 11.7% E. coli—1.2× and 7.8× routine rates—with higher contamination inside flood boundaries.
Source
Using Inundation Extents to Predict Microbial Contamination in Private Wells after Flooding Events
Study at a glance
- Design
- Cross-sectional — Post–Hurricane Florence private-well tests overlaid on FEMA/HAND/DFO inundation maps
- N
- N=754 · 754 well samples after Florence included after exclusions
- Population
- Private wells in FEMA-designated North Carolina counties after Hurricane Florence
- Outcome
- Total coliform and E. coli positivity inside vs outside flood inundation extents
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
North Carolina private-well tests after Florence were overlaid on FEMA 100-year, HAND, and DFO inundation extents to compare TC/EC positivity inside vs outside each flood product.
What they found
About 20.7% of 2.5 million FEMA-county residents (518,000 people) used private wells. Inside vs outside flood boundaries, contamination was up to 1.2× (TC) and 10.9× (EC) higher, but products disagreed (TC 40.8–53.1%; EC 10.5–16.3%) and no map caught all positives. The 100-year floodplain was 2.9–7.9× larger than HAND/DFO.
The limits
What it doesn't show
Testing was not a complete census of wells; people who test after disasters are a selected sample, so rates may not equal true population risk.
Key terms
- Total coliform (TC)
- Indicator bacteria suggesting well-water contamination.
- E. coli (EC)
- Fecal-indicator bacterium implying greater pathogen risk.
- HAND
- Height Above Nearest Drainage inundation model.
- DFO
- Dartmouth Flood Observatory satellite flood mapping.
- 100-year flood boundary
- FEMA floodplain used here as a large inundation mask.
Flashcards
Research intelligence for this paper
See its role on concept claims, tensions it is part of, placement history, and related discoveries.
Quiz yourself
Post-Florence E. coli positivity was about:
Common questions
Post-Florence TC/EC rates?
41.2% TC and 11.7% EC.
Vs routine?
1.2× TC and 7.8× EC.
Did flood maps agree?
No—different positives and different areas.
Private-well users in FEMA counties?
~518,000 (20.7%).
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