Flood Damage Estimator Calculator

The calculator subtracts an effective-depth offset based on foundation before applying the depth-damage curve: 0 ft for slab-on-grade, 1 ft for crawlspace, and 3 ft for elevated/pier construction, reflecting that floodwater must rise past the crawlspace or pier height before it reaches living space. A basement gets no offset — instead its already-computed structural and contents damage percentages are multiplied by 1.5, since underground flooding submerges finishes and mechanical systems that were never built to get wet.

Every other foundation type shifts the effective depth used in the USACE curve up before computing damage percentages. A basement keeps the raw flood depth but multiplies the resulting structural and contents damage percentages by 1.5 afterward, because a given depth of water does proportionally more harm below grade — finishes, wiring, and mechanicals sit lower there and take longer to dry out — not because the damage curve itself starts higher.

They're modeled on the depth-damage curves used in FEMA's Hazus flood loss estimation model, which credits the US Army Corps of Engineers (specifically the Corps' Institute for Water Resources and Chicago District studies) as source data for how structure damage percentage rises with flood depth. That's why the curve isn't a straight line — it reflects how a real flood destroys progressively more expensive building systems as the water gets deeper, not a simple percentage-per-foot rule.

No — it's a simplified cap-based estimate, not an actuarial claim value. When flood insurance is toggled on, the calculator pays out the lesser of your computed structural damage (plus mold and drying costs) or NFIP's $250,000 structure limit, and separately the lesser of your contents damage or the $100,000 contents limit. A real NFIP claim also depends on your specific policy's coverage limits, deductible, and an adjuster's verified loss assessment, none of which this calculator can see.

At one foot of effective depth the contents curve reaches 15% while the structural curve only reaches 12.5%, and the gap widens through the middle tiers because furniture, electronics, and belongings sitting near the floor are damaged or destroyed by water levels that only affect flooring and baseboards structurally. Both curves converge near a 95% cap at the highest depths, where nearly everything in the home is compromised regardless of category.