House design · Structure and hazards: wind, earthquake, flood and wildfire · design-27

Build to resist floods

Avoiding the flood zone is best. Where you cannot, raise the house, use materials that survive floodwater and plan how to recover.

How

First choice: build outside mapped flood zones and away from low ground (site-3, site-6).
FEMA P-312 lists six ways to protect a home: elevation, wet floodproofing, dry floodproofing, relocation, levees and floodwalls, and demolition and rebuilding.
Elevation means raising the lowest floor above the flood level. Your local flood rules set the design flood elevation, often the base flood level plus freeboard.
Below that level use flood damage-resistant materials. FEMA defines them as products that survive direct, prolonged floodwater contact with no more than cosmetic repair.
Wet floodproofing lets water into uninhabited spaces built from such materials. Dry floodproofing seals the building so water stays out.
UK example: the CIRIA code of practice C790 separates resistance measures (keep water out) from recoverability measures (limit damage if water gets in).
Keep batteries, inverters, panels and water treatment above the design flood level (power and water modules).