St. Mary's County, MD flood risk explained
Flood hazard in St. Mary's County sits at the 63th national percentile, a middling flood hazard by national standards; driven by coastal storm surge rather than inland rivers — FEMA's model puts a surge event here at about 3.6 times a year. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Mandatory flood insurance compliance in St. Mary's County
Homes with a federally backed mortgage inside St. Mary's County's mapped high-risk flood zone (the Special Flood Hazard Area, or SFHA) are legally required to carry an NFIP flood policy. In practice, 55.2% of them do — 528 active policies against 957 structures FEMA counts in that zone, leaving a real compliance gap. Looking beyond the mandated zone, 2.4% of all residential structures in St. Mary's County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
St. Mary's County against the rest of the country
Among the 3144 US counties FEMA scores for flood hazard, St. Mary's County ranks 1213 — 1 being the highest hazard nationally — and 546 by population among all 3144 counties covered here, where 1 is the largest. St. Mary's County, Maryland covers 358.589 square miles and counts roughly 116,469 residents.
Your street may differ from St. Mary's County's average
Across all of St. Mary's County's 41,939 residential structures, 990 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where St. Mary's County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. St. Mary's County's coastal exposure is covered in the coastal vs. inland flood risk guide, including how storm surge risk differs from river flooding.