Top 60 Flood Terms: Decoded Without the Jargon

Definition: A flood with a 1% chance of being equaled or exceeded in any given year. It can happen more than once in a lifetime.

Importance: Many rules, maps, and insurance prices are based on this benchmark.

Definition: The specific 1% annual-chance flood used for mapping and building standards.

Importance: Sets design targets for new/renovated buildings in risky areas.

Definition: The water surface height (relative to a survey datum) reached by the base flood.

Importance: First-floor elevation vs. BFE strongly influences insurance cost and code requirements.

Definition: Extra height (often +1–3 ft) above BFE to hedge against uncertainty and waves.

Importance: Low-cost way to reduce damage and premiums; often required by local codes.

Definition: Special Flood Hazard Area (≥1% risk). AE = stillwater flooding; VE = coastal with waves; X = lower risk.

Importance: Lenders may require insurance in SFHAs; VE zones have stricter build rules.

Definition: Floodway = channel + fast-flow area needed to carry the base flood; Fringe = shallower overflow areas.

Importance: Building in the floodway is highly restricted due to velocity and blockage risks.

Definition: Official map showing flood zones, BFEs, and floodways.

Importance: Determines insurance requirements and local building standards.

Definition: Letter of Map Amendment (LOMA) or Revision (LOMR) to correct or update FIRMs.

Importance: Can remove a home from SFHA (and lender insurance requirement) or update BFEs.

Definition: Surveyed form showing a building’s elevations relative to BFE.

Importance: Supports accurate insurance rating and code compliance.

Definition: The vertical reference system used for elevations.

Importance: Ensures apples-to-apples comparisons between BFE, surveys, and maps.

Definition: The floor used for rating—often the top of the lowest enclosed area (with rules for enclosures).

Importance: Drives premiums; enclosing space below BFE can raise costs.

Definition: When repairs or upgrades ≥ ~50% of market value, the building must meet current flood codes.

Importance: Can require elevation or floodproofing during big renovations.

Definition: Voluntary program where towns earn points for better flood practices.

Importance: Residents get automatic insurance discounts in CRS communities.

Definition: Modernized NFIP pricing that uses multiple risk factors (distance to water, elevation, foundation type, etc.).

Importance: Premiums better reflect individual property risk, not just zone.

Definition: Amount you pay out of pocket before insurance coverage begins.

Importance: Higher deductibles lower premiums but increase what you owe after a flood.

Definition: Time between purchase and coverage start (NFIP commonly ~30 days).

Importance: You can’t buy the day before a storm and be covered.

Definition: Replacement Cost = new for old; ACV = depreciated value.

Importance: Policy type changes payout size—big deal for major losses.

Definition: Actions that reduce future flood damage (elevate, floodproof, relocate).

Importance: Can cut premiums and disaster downtime; sometimes grant-eligible.

Definition: Dry keeps water out (seals/barriers). Wet allows water in but minimizes damage (vents, flood-resistant materials).

Importance: Choice depends on building type, depth, and code limits.

Definition: One-way valve that stops sewage or stormwater from backing into a home.

Importance: Critical in low areas where mains surcharge during storms.

Definition: Pump removes water from a pit; backup keeps it running during outages.

Importance: Prevents basement flooding when power fails—the most common time.

Definition: How a home meets the ground—affects lowest floor and water pathways.

Importance: Different types have different code/mitigation requirements and premiums.

Definition: Openings that let water flow through enclosed areas to equalize pressure.

Importance: Prevents wall collapse and can improve insurance rating for enclosures.

Definition: Removal of soil around foundations/bridge piers by fast water.

Importance: Undermines structures; dictates deeper footings or protection.

Definition: Required distance from eroding banks or shorelines.

Importance: Reduces long-term loss risk and protects natural buffers.

Definition: Laser-based mapping used to build detailed ground elevation models.

Importance: Improves flood mapping accuracy and site planning.

Definition: Surge = coastal water pushed inland; Riverine = rivers/streams overflow; Pluvial = intense rain overwhelms drainage away from rivers.

Importance: Different defenses and maps apply to each hazard.

Definition: Premium reductions for building above BFE.

Importance: Each added foot can meaningfully reduce annual cost.

Definition: FEMA recognizes (or “provisionally accredits”) levees that meet standards.

Importance: Affects mapped risk and insurance, but residual risk remains behind levees.

Definition: Engineer’s proof that a project in the floodway won’t increase base flood heights.

Importance: Required for many floodway projects to avoid worsening neighbors’ risk.