FloodGap

When a major flood hits western North Carolina, who is vulnerable, and where should relief sites go?

Why western NC floods so badly

Mountains squeeze out extra rain. Moist storm air is pushed up the Blue Ridge, cools, and drops more rain.
Steep slopes funnel water into narrow valleys, so rivers like the French Broad and Swannanoa rise fast.
Towns and roads sit in those valleys, because that's where the flat land is.
Many places have only one or two roads out. When they wash out, people are stranded.

In September 2024, Hurricane Helene did exactly this. Switch between Normal day and Major flood above to see it happen on the map.

Flood-prone land: FEMA's flood maps, built from past rainfall, river, and elevation data. We use their largest mapped flood area to stand in for a Helene-sized storm.
Closed roads: every road in that flood area is treated as impassable.
Who's cut off: for each Census neighborhood, we compare the drive time to the nearest hospital, clinic, or fire station on a normal day and in the flood.
Where to act: we test schools, community centers, places of worship, and libraries outside the flood area, and pick the ones that bring the most stranded people within 15 minutes of help.

Show on map Flood-prone areas Closed roads Cut-off neighborhoods Hospitals, clinics, fire stations Recommended relief sites