What Flood Damage Estimation Does

The Damage Estimation module converts flood depth into estimated monetary damage for a specific building. It answers: “If water reaches this depth at this building, how much damage should I expect?”

This module does not determine flood depth — that comes from the Flood Depth module or is provided directly by the user. Damage Estimation applies published depth-damage functions (curves that map water depth to percentage of building value damaged) to produce damage ratios and monetary loss estimates.

Each analysis returns results from two independent damage models: FEMA HAZUS 4.0 (US-focused) and JRC Huizinga et al. 2017 (international). Both are provided for every analysis, allowing comparison.

The Two Damage Models

FEMA HAZUS 4.0 (US-Focused)

HAZUS is FEMA’s official loss estimation methodology for natural hazards in the United States. The flood component contains 196 depth-damage curves covering 33 building occupancy types with variations for stories, basement presence, and flood zone type.

HAZUS is calibrated to US building stock only. The underlying data is derived from US Army Corps of Engineers (USACE) and Federal Insurance Administration (FIA) damage surveys. Applying HAZUS curves to non-US buildings is not recommended.

The 33 occupancy types span seven categories: Residential (RES1-RES6), Commercial (COM1-COM10), Industrial (IND1-IND6), and Other (AGR1, REL1, GOV1-2, EDU1-2).

HAZUS curves cover depths from -4 to +24 feet relative to the first finished floor, using 29 depth points at one-foot intervals. Negative depths represent water below the first floor (relevant for basements). Structural and contents damage are computed separately.

JRC Huizinga et al. 2017 (International)

The JRC damage functions are published by the European Commission’s Joint Research Centre for global use. They provide depth-damage relationships for 214 countries with country-specific maximum damage values (in EUR per square metre, 2010 prices).

JRC covers six building sectors: residential, commercial, industrial, agriculture, transport, and infrastructure. Curves cover depths from 0 to 6 metres. JRC combines structural and contents damage into a single ratio, unlike HAZUS which separates them.

When a country-specific curve is unavailable, the system falls back to the continental average, then global average. Results indicate whether a fallback was applied.

Why Both Are Provided

HAZUS and JRC represent different methodological traditions. HAZUS measures structural damage only (contents are separate); JRC combines them. HAZUS uses user-provided replacement values in USD; JRC uses country-average maximum damage in EUR 2010. For US properties, HAZUS is more granular. For international properties, JRC provides the only standardised framework.

Understanding the Inputs

Flood depth (required) is the water level above grade in feet. This is the primary driver of damage.

Occupancy type (HAZUS) determines which of the 33 curves to use. Sector (JRC) is derived from the occupancy type.

Building characteristics that modify the calculation include: number of stories (damage distributed across more floors), basement (changes starting depth), flood zone type (riverine, coastal A, coastal V), floor area (JRC scaling), replacement value (HAZUS basis), and content value.

First Floor Height (FFH) is the vertical distance from ground to lowest habitable floor. It is the single most impactful input after depth itself because it determines whether floodwater actually enters the building. A building with FFH of 4 feet in 3 feet of floodwater has negative depth-in-structure — minimal damage.

When optional inputs are not provided, the system applies documented defaults based on building type and configuration. Providing actual values (especially FFH) significantly improves accuracy. Results include transparency flags when defaults are applied or curves are substituted.

Understanding the Outputs

The damage ratio (0.0 to 1.0) represents the fraction of building value that is damaged. A ratio of 0.35 means 35% estimated damage.

For HAZUS, structural damage (walls, foundation, roof, systems) and contents damage (furniture, equipment, inventory) are reported separately. At moderate depths, contents damage often exceeds structural damage because furnishings are more vulnerable to water.

Absolute monetary loss is damage ratio multiplied by replacement value (HAZUS) or by maximum damage per m² multiplied by floor area (JRC).

The depth-damage curve chart shows the relationship between water depth and damage percentage. The curve follows a characteristic shape: minimal damage at very low depths, a rapid increase as water first enters the building, a zone of high sensitivity, and a gradual plateau as damage approaches its maximum. Understanding this shape helps assess where depth uncertainty matters most.

Batch Estimation

Damage estimation supports batch processing for up to 5,000 buildings per request. Unlike geospatial modules, damage estimation is computed from in-memory reference data — sub-millisecond per building. A 5,000-building batch completes in under one second. Results can be exported as CSV.

Limitations

Depth-damage functions are statistical averages. Individual buildings may experience one-third to three times the curve estimate depending on construction quality, maintenance, and contents placement.

HAZUS curves are US-calibrated and may not reflect non-US construction. JRC uses continental averages with significant within-continent variation. JRC maximum damage values are in 2010 EUR and not inflation-adjusted.

Loss types not captured: business interruption, temporary displacement, infrastructure damage, environmental remediation, mould/long-term moisture damage, and cascading economic effects. The estimation assumes clean freshwater — saltwater, sewage, sediment, debris, and high-velocity flow cause additional damage not reflected in the curves. Flood duration is also not considered.

Frequently Asked Questions

“Why do HAZUS and JRC give different damage amounts?”
Different approaches, damage scopes (structural-only vs combined), classifications (33 types vs 6 sectors), and currencies (USD vs EUR 2010). They are complementary, not competing. Use HAZUS for US, JRC for international.

“Can I use HAZUS curves for non-US buildings?”
Not recommended. HAZUS is derived from US building surveys. Non-US buildings with different materials (e.g., reinforced concrete vs wood frame) may sustain very different damage at the same depth. Use JRC for international buildings.

Appropriate use: Portfolio-level flood loss screening, order-of-magnitude estimates, comparative analysis across buildings or locations, insurance screening support, TCFD climate risk quantification.

Not suitable for: Insurance-grade loss quantification, engineering damage assessment, individual claims adjustment, financial reporting without additional professional validation.