INDIANA — The Indiana Department of Natural Resources (DNR) Division of Water has completed its July 2026 update to the state’s Best Available Flood Hazard Layer, incorporating revised hydraulic modeling and updated stream boundaries across 12 Hoosier counties.
The updates affect specific waterways and stream reaches, providing property owners, developers, and local government officials with the most current modeling available to evaluate flood risks and navigate local permitting requirements.
Affected Counties and Streams
The July 2026 revisions reflect updated modeling for specific stream segments in the following areas:
- Allen County: UNT Grover Ditch
- Boone County: Wells Ditch
- Gibson County: Coffee Bayou
- Greene County: Flyblow Branch
- Hamilton County: Sly Run East Fork Creek
- Lawrence County: UNT Indian Creek
- Monroe County: Indiana Creek
- Orange County: UNT South Fork Beaver Creek
- Pike County: Lick Creek
- St. Joseph County: UNT Dixon West Place Ditch
- Warrick County: Plum Branch
- Washington County: NC Area
Understanding “Best Available” Data vs. FEMA Maps
The DNR Division of Water routinely updates the Best Available Flood Hazard Layer by merging official Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs) with supplemental engineering studies, hydraulic model reviews, and local “Zone A” mapping projects.
Key distinctions between mapping layers include:
- Regulatory & Permitting Use: While FEMA FIRMs are used strictly for federal flood insurance requirements, Indiana’s Best Available data defines state jurisdiction under the Indiana Flood Control Act and assists local planning departments in enforcing community floodplain management ordinances.
- Increased Coverage: The state’s ongoing mapping initiative adds detailed Base Flood Elevations (BFEs) and approximate floodway boundaries to thousands of miles of smaller streams and tributaries that have not yet undergone formal FEMA publication.
- General Planning: Because Best Available data contains the most recently reviewed studies, state officials advise utilizing these updated layers for general site planning, construction proposals, and hazard mitigation efforts.
Accessing Map Services and Public Tools
Property owners, engineers, and GIS specialists can access and review the updated flood hazard data through several state portals:
- ArcGIS REST Services: GIS professionals can integrate the raw spatial layer directly into custom mapping applications via the DNR Best Available Flood Hazard Layer Server.
- Indiana Floodplain Information Portal (INFIP): The public can view interactive map overlays and generate site-specific Floodplain Analysis and Regulatory Assessment (FARA) reports by visiting the Indiana DNR Division of Water Page.
