Charleston County, SC flood risk explained
Flood hazard in Charleston County sits at the 99.8th national percentile, among the highest flood hazard in the country; split between inland river flooding (about 3.5 times a year) and coastal storm surge (about 3.6 times a year). This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
Charleston County's flood-insurance compliance gap
Out of 44,952 homes FEMA counts inside Charleston County's mapped flood zone, 35,189 carry the flood policy federal law requires there — 78.3% compliance, short of full coverage. Looking beyond the mandated zone, 31.7% of all residential structures in Charleston County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
How Charleston County compares nationally
Among the 3144 US counties FEMA scores for flood hazard, Charleston County ranks 10 — 1 being the highest hazard nationally — and 173 by population among all 3144 counties covered here, where 1 is the largest. Charleston County, South Carolina is home to about 431,001 people across 918.147 square miles of land.
Checking a specific address in Charleston County
Across all of Charleston County's 148,009 residential structures, 46,856 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where Charleston County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. Charleston County's coastal exposure is covered in the coastal vs. inland flood risk guide, including how storm surge risk differs from river flooding.