When a flood hits a commercial building, the first question insurance companies, banks, and risk managers ask is: how much damage? HAZUS is FEMA’s answer. It provides standardized depth-damage curves that estimate building losses at any flood depth, for any building type, across three different flood zones.
This guide explains what HAZUS is, how its 196 depth-damage curves work, what the 33 building types mean, why first floor height changes everything, and how financial institutions use HAZUS curves for portfolio-level flood risk assessment.
What Is HAZUS?
HAZUS stands for Hazards United States. FEMA developed it as a GIS-based tool for estimating losses from natural hazards, including floods, earthquakes, and hurricanes. The flood module is the most widely used component, and it’s what this article focuses on.
FEMA created HAZUS to standardize how the US estimates disaster losses. Before HAZUS, every local emergency manager used different methods, different assumptions, and different data. HAZUS gave them a common framework: one set of damage curves, one building taxonomy, one methodology. Over 10,000 emergency planners, insurers, and risk analysts have used it since its initial release.
The current version is HAZUS 7.0, which runs on ArcGIS Pro. But the damage curves inside HAZUS are independent of the software. They’re published datasets that any system can use, and that’s exactly what makes them valuable outside FEMA’s desktop application.
HAZUS 4.0 contains the depth-damage functions most widely cited in the literature: 196 individual curves covering 33 building types, three flood zones, and two coverage types (structure and contents). The curve data traces back to NFIP claims records collected by the Federal Insurance Administration (FIA) and empirical studies by the US Army Corps of Engineers (USACE).
HAZUS Depth-Damage Curves Explained
What Is a Depth-Damage Curve?
A depth-damage curve is a function that maps flood depth to damage percentage. You input the water depth at a building, and the curve returns the fraction of the building’s value that gets destroyed at that depth. The output is a damage ratio between 0.0 (no damage) and 1.0 (total loss).
These curves follow a characteristic sigmoid (S-shaped) pattern. Below the first finished floor, damage is minimal or zero for buildings without basements. Between 0 and 2 feet above the first floor, damage initiates rapidly as water contacts flooring, baseboards, and electrical outlets. From 2 to 8 feet, damage climbs steeply as water reaches HVAC systems, walls, and progressively higher contents. Above 8 feet, the curve flattens because the building’s structural frame, foundation, and roof survive even deep flooding.
196 Curves Across Three Flood Zones
HAZUS doesn’t provide a single generic damage curve. It provides 196 of them, organized across three dimensions:
- 33 occupancy types (building categories from single-family homes to heavy industrial facilities)
- 3 flood zones: Riverine (stillwater from rivers and streams), Coastal A (coastal with moderate 1-3 foot waves), and Coastal V (coastal with high-velocity 3+ foot waves)
- 2 coverage types: Structure (the building itself) and Contents (everything inside it)
Coastal V zones produce the highest damage at any given depth because wave impact and velocity forces compound the hydrostatic pressure damage. A building at 4 feet of flooding in a Coastal V zone will sustain more damage than the same building at 4 feet in a riverine zone.
How to Read a HAZUS Curve
Each HAZUS curve contains 29 data points at 1-foot intervals from -4 to +24 feet. The depth axis measures water level relative to the first finished floor, not relative to ground level. A depth of 0 means water is exactly at floor level. Negative depths (-4 to -1) capture basement flooding for buildings with basements.
The damage axis shows percentage of replacement value. A structural damage value of 30 at depth 4 means 30% of the building’s structural replacement cost is destroyed at 4 feet of flooding above the first floor. Between the 29 integer depth points, damage is calculated using linear interpolation.
Key observations from the curves:
- Structural damage maxes out at approximately 50-65% even at extreme depths because the building frame and foundation survive complete inundation
- Contents damage can reach 80-100% because ground-floor items are destroyed at relatively shallow depths
- Two-story buildings show lower damage ratios than one-story buildings at the same depth because upper-floor contents stay dry
- All curves are monotonically non-decreasing: more water never reduces damage
The 33 HAZUS Building Types
HAZUS classifies every building into one of 33 specific occupancy types across 7 categories. Each occupancy type has its own set of depth-damage curves because different building uses sustain different levels of damage at the same flood depth.
Residential (12 Types)
The residential category covers everything from single-family homes to nursing homes:
- RES1: Single Family Dwelling (the most commonly modeled type, with curves for 1-story, 2-story, 3+ story, and split-level)
- RES2: Mobile Home / Manufactured Housing (higher vulnerability, pier/block foundations)
- RES3A through RES3F: Multi-Family Dwellings ranging from duplexes (3A) to 50+ unit complexes (3F)
- RES4: Temporary Lodging (hotels and motels)
- RES5: Institutional Dormitory
- RES6: Nursing Home
Commercial (10 Types)
Commercial buildings cover the full range of business occupancies:
- COM1: Retail Trade
- COM2: Wholesale Trade (warehouses, distribution centers)
- COM3: Personal and Repair Services
- COM4: Professional/Technical/Business Services (office buildings)
- COM5: Banks and Financial Institutions
- COM6-COM7: Hospital and Medical Office/Clinic
- COM8-COM9: Entertainment/Recreation and Theaters
- COM10: Parking
Industrial and Other (11 Types)
The remaining categories cover industrial, agricultural, religious, government, and educational buildings:
- IND1-IND6: Heavy Industrial through Construction
- AGR1: Agriculture
- REL1: Church / Religious / Non-Profit
- GOV1-GOV2: General Government and Emergency Response
- EDU1-EDU2: Schools (K-12) and Colleges/Universities
Why Occupancy Type Matters
A warehouse (COM2) and an office building (COM4) respond differently to the same flood. Warehouses store inventory at ground level, so shallow flooding destroys high-value goods immediately. Office buildings keep most equipment on desks and shelves, so damage initiates at higher depths.
Contents value ratios also differ by occupancy type. HAZUS defaults assume residential contents are worth 50% of the building’s replacement value, commercial contents equal 100%, and industrial contents reach 150% (machinery and raw materials often exceed the building’s structural value). These ratios significantly affect total commercial flood damage estimates.
First Floor Height and Why It Matters
What Is First Floor Height?
First floor height (FFH) is the vertical distance from ground grade to the first finished floor of a building. HAZUS depth-damage curves measure flood depth relative to the first finished floor, not relative to the ground. This means FFH acts as a critical offset: it determines how much flooding at ground level actually reaches the building’s living or working space.
HAZUS Default FFH Values
When users don’t specify FFH, HAZUS applies defaults based on building characteristics:
- Buildings with basements: 4.0 feet (the first finished floor sits 4 feet above grade, with the basement below)
- Manufactured housing (RES2): 3.0 feet (pier or block foundations raise the unit above grade)
- All other buildings: 1.0 foot (standard slab-on-grade construction)
These defaults come from a 2021 USACE economist survey of foundation characteristics documented in the HAZUS Inventory Technical Manual.
Impact on Damage Estimation
First floor elevation creates dramatically different outcomes at the same flood depth. Consider 3 feet of flooding at ground level:
- A slab-on-grade office (1-foot FFH) has 2 feet of water inside the first floor. At that depth, HAZUS estimates roughly 15-20% structural damage.
- A building with a basement (4-foot FFH) has water only in the basement, 1 foot below the first floor. Structural damage to the first floor is near zero, though basement contents and mechanical systems take losses.
This is why flood damage estimates are meaningless without knowing first floor height. Two identical buildings on the same block with different foundations will produce completely different loss numbers.
HAZUS Versions: From HAZUS-MH to HAZUS 7.0
Legacy: HAZUS-MH
HAZUS-MH (Multi-Hazard) was the original multi-hazard version of HAZUS, built for ArcMap. It combined flood, earthquake, and hurricane loss estimation in a single desktop application. Many older academic papers and government reports still reference HAZUS-MH, and the term appears frequently in literature searches.
HAZUS 4.0 Through 7.0
HAZUS 4.0 (2018) updated the depth-damage curve data using FIA claims records and USACE empirical studies. These are the curves most commonly cited in peer-reviewed flood risk research and the ones used in most commercial implementations.
HAZUS 7.0, the current release, migrated the platform from ArcMap to ArcGIS Pro. The underlying damage curves remain consistent with HAZUS 4.0, but the software interface, data management, and processing engine were rebuilt for the modern ArcGIS platform.
Downloading HAZUS
HAZUS is free to download from the FEMA Map Service Center. The catch: it requires an ArcGIS Pro license, which costs thousands of dollars per year. This makes HAZUS effectively inaccessible to organizations that don’t already use Esri’s GIS platform.
The alternative is using the underlying HAZUS damage curves through an API. Continuuiti’s damage estimation tool implements the same HAZUS 4.0 curves and adds JRC global coverage, allowing users to estimate flood damage for any building type without installing desktop GIS software.
HAZUS vs. JRC: US Curves vs. Global Curves
HAZUS covers the United States. For buildings outside the US, a different set of curves is needed. The most widely used alternative is the JRC Huizinga methodology, published by the European Commission’s Joint Research Centre.
HAZUS (United States)
- 33 specific occupancy types with building-level granularity
- Structure and contents damage calculated separately
- Depth range: -4 to +24 feet (captures basement flooding)
- 29 data points at 1-foot intervals
- No uncertainty bounds (all values are deterministic point estimates)
JRC Huizinga (Global)
- 6 broad sectors (residential, commercial, industrial, agriculture, transport, infrastructure)
- 7 continental groupings covering 214 countries
- Structure and contents combined into a single damage ratio
- Depth range: 0 to 6 meters (no basement modeling)
- 9 data points at non-uniform spacing
- Standard deviations available for some continent/sector combinations
The two methodologies are not directly comparable. HAZUS structural damage at 4 feet might read 25%, while JRC combined damage at the same depth reads 45%. This difference reflects their measurement basis: HAZUS measures structural damage alone against user-provided replacement value, while JRC measures total damage (structure plus contents) against a country-average maximum damage value in EUR per square meter.
HAZUS for Financial Risk Assessment
HAZUS was built for emergency planners, but financial institutions have adopted its curves for a different purpose: quantifying flood exposure across building portfolios.
Portfolio-level damage estimation. Banks with thousands of commercial real estate loans run HAZUS curves across their entire book to identify concentration risk. Which loans have the highest flood exposure? Which regions carry the most aggregate loss potential? HAZUS curves answer these questions at the individual property level.
TCFD and ISSB climate disclosure. Both frameworks require quantified, scenario-based financial impact analysis. HAZUS curves feed directly into climate value at risk calculations by providing the vulnerability component: how much damage does this building type sustain at this flood depth?
Insurance underwriting. Insurers use HAZUS-style curves to price flood coverage and set portfolio reserves. The curves provide a standardized baseline for estimating probable maximum loss across an insured portfolio.
Mortgage risk screening. Lenders screen mortgage applications against HAZUS curves to flag properties with high flood damage potential before approving loans. Properties in high-risk zones may require additional flood insurance or higher reserves.
The common thread: HAZUS curves translate a physical hazard (flood depth) into a financial metric (damage as percentage of value). That translation is what makes flood risk calculable, comparable, and actionable for financial decision-making.
Frequently Asked Questions
What does HAZUS stand for?
HAZUS stands for Hazards United States. FEMA developed it as a GIS-based tool for estimating losses from floods, earthquakes, and hurricanes. The flood module and its depth-damage curves are the most widely used components.
What is a HAZUS damage function?
A HAZUS damage function maps flood depth to building damage as a percentage of replacement value. Each curve has 29 data points at 1-foot intervals from -4 to +24 feet relative to the first finished floor. Damage follows a sigmoid pattern: minimal below the floor, steep between 0-8 feet, flattening above 8 feet.
How many building types does HAZUS include?
HAZUS includes 33 occupancy types in 7 categories: Residential (12), Commercial (10), Industrial (6), Agriculture (1), Religious (1), Government (2), and Education (2). Each type has its own depth-damage curves for both structure and contents.
Can HAZUS be used outside the United States?
HAZUS curves are based on US building construction practices, so applying them internationally introduces systematic bias. For global flood damage estimation, the JRC Huizinga methodology covers 214 countries with continent-specific damage functions across 6 building sectors.
Is HAZUS free to download?
The HAZUS software is free from FEMA’s Map Service Center, but it requires an ArcGIS Pro license to run. The underlying damage curve data is publicly available and can be accessed through APIs without the desktop software.
What is the difference between structural and contents damage?
HAZUS calculates them separately. Structural damage covers the building itself (walls, floors, foundation, mechanical systems) and typically maxes out at 50-65% because the frame survives deep flooding. Contents damage covers everything inside (furniture, equipment, inventory) and can reach 80-100% since ground-floor items are destroyed at shallow depths.
