Building Code Glossary
Floodway: Building Code Definition
How the IBC 2009 define floodway, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.
Direct answer
Floodway is a defined term in the International Building Code (IBC) 2009, in Structural Design. The code's own words are: “The channel of the river, creek or other water-course and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.” No other I-Code in this corpus defines it, so the IBC 2009 definition is the one to work from. The term is used in 6 chapters of this corpus, most often in Structural Design (IBC 2009), Building Planning (IRC 2009), Scope and Administration (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted.
Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Floodway — IBC 2009, Structural Design:
The channel of the river, creek or other water-course and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.
What must be verified before using this guidance?
Floodway is defined once in this corpus, in the Structural Design chapter of the International Building Code (IBC) 2009:
The channel of the river, creek or other water-course and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.
Where floodway is used in the code
The term appears in 6 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Structural Design | IBC 2009 | 13 |
| Building Planning | IRC 2009 | 10 |
| Scope and Administration | IRC 2009 | 4 |
| Scope and Administration | IBC 2009 | 2 |
| Soils and Foundations | IBC 2009 | 2 |
| Definitions | IBC 2009 | 1 |
The term in use
How the code actually writes about floodway, quoted from the 2009 text hosted here:
The flood hazard map shall include, at a minimum, areas of special flood hazard as identified by the Federal Emergency Management Agency in an engineering report entitled "The Flood Insurance Study for [INSERT NAME OF JURISDICTION]," dated [INSERT DATE OF ISSUANCE], as amended or revised with the accompanying Flood Insurance Rate Map (FIRM) and Flood Boundary and Floodway Map (FBFM) …
The terms floodway is built out of
The definition above leans on 1 other defined term. Each carries its own code definition, and a local amendment to any of them changes what floodway covers:
- Base Flood — IBC 2009: The flood having a I-percent chance of being equaled or exceeded in any given year.
Floodway: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IBC | Structural Design | |
| Re-check the requirement that uses it | Structural Design (IBC 2009) | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IRC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IBC 2009) | |
| Confirm the dependent definition | Base Flood | |
| Local amendment to any of the above | Jurisdiction's amendment list |
A research aid, not a code determination. The authority having jurisdiction decides which edition and which amendments apply.
Where can you explore related guidance?
- Explore all glossary guidance
- Base Flood: Building Code Definition
- Design Flood Elevation: Building Code Definition
- Loads: Building Code Definition
- Seismic Design Category: Building Code Definition
Sources and method
Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The ICC code library publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of floodway?
The International Building Code (IBC) 2009 defines it in Structural Design as: “The channel of the river, creek or other water-course and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.
Which parts of the code depend on floodway?
In this corpus the term is used across 6 chapters, led by Structural Design in the IBC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.
What is considered a floodway?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Structural Design: “The channel of the river, creek or other water-course and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.” It is defined in IBC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
Related pages
- Flood Insurance Rate Map (FIRM): Building Code Definition
Flood Insurance Rate Map (FIRM) — IBC 2009 definition: An official map of a community on which the Federal Emergency Management Agency (FEMA) has delineated …
- Flood Insurance Study: Building Code Definition
Flood Insurance Study — IBC 2009 definition: The official report provided by the Federal Emergency Management Agency containing the Flood Insurance Rate Map …
- Flood Level Rim: Building Code Definition
Flood Level Rim — IPC 2009 definition: The edge of the receptacle from which water overflows.
- Floor Area, Gross: Building Code Definition
Floor Area, Gross — IBC 2009 definition: The floor area within the inside perimeter of the exterior walls of the building under consideration …
- Floor Area, Net: Building Code Definition
Floor Area, Net — IBC 2009 definition: The actual occupied area not including unoccupied accessory areas such as corridors, stairways, toilet rooms, mechanical …
- Floor Drain: Building Code Definition
Floor Drain — IRC 2009 definition: A plumbing fixture for recess in the floor having a floor-level strainer intended for the purpose …